* Re: [RFC] Thread Migration Preemption - v2
2007-07-11 16:36 ` Oleg Nesterov
@ 2007-07-14 18:27 ` Mathieu Desnoyers
2007-07-14 19:56 ` Oleg Nesterov
2007-07-14 18:40 ` [RFC] Thread Migration Preemption - v3 Mathieu Desnoyers
2007-07-14 18:42 ` [RFC] Thread Migration Preemption - v4 Mathieu Desnoyers
2 siblings, 1 reply; 16+ messages in thread
From: Mathieu Desnoyers @ 2007-07-14 18:27 UTC (permalink / raw)
To: Oleg Nesterov; +Cc: linux-kernel, Ingo Molnar, Steven Rostedt
* Oleg Nesterov (oleg@tv-sign.ru) wrote:
> On 07/11, Mathieu Desnoyers wrote:
> >
> > This patch adds the ability to protect critical sections from migration to
> > another CPU without disabling preemption.
> >
> > This will be useful to minimize the amount of preemption disabling for the -rt
> > patch. It will help leveraging improvements brought by the local_t types in
> > asm/local.h (see Documentation/local_ops.txt). Note that the updates done to
> > variables protected by migrate_disable must be either atomic or protected from
> > concurrent updates done by other threads.
> >
> > Typical use:
> >
> > migrate_disable();
> > local_inc(&__get_cpu_var(&my_local_t_var));
> > migrate_enable();
> >
> > Which will increment the variable atomically wrt the local CPU.
>
> Well, I am not a maintainer, but I personally think this patch is too complex.
>
> Mathieu, please use "diff -p", it is very difficult to read it. I am not sure
> I understand this patch correctly, I don't have a -git tree.
>
man quilt... echo "QUILT_DIFF_OPTS="-p" > ~/.quiltrc. done. :) Thanks
for pointing this out, the next patches should include this.
> > static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
> > {
> > @@ -4829,13 +4888,19 @@
> >
> > double_rq_lock(rq_src, rq_dest);
> > /* Already moved. */
> > - if (task_cpu(p) != src_cpu)
> > + if (task_cpu(p) != src_cpu) {
> > + ret = 1;
> > goto out;
> > + }
>
> This is a strange change. Why we return success when migration failed ?
> OK, I guess this is a special hack for the modified migration_thread()...
>
Yes, I wanted to change __migrate_task so it returns true if, after it
has been called to migrate a task out of a source CPU, the task is
indeed now migrated out the this CPU.
It follows a comment already at the beginning of this function:
* So we race with normal scheduler movements, but that's OK, as long
* as the task is no longer on this CPU.
The comment at the beginning explains the new convention:
- * Returns non-zero if task was successfully migrated.
+ * Returns non-zero if task is on dest_cpu when this function ends.
Well.. my comment is not perfect. It should read:
- * Returns non-zero if task was successfully migrated.
+ * Returns non-zero if task is not on src_cpu when this function ends.
My assumption is that if migrate_task races with the scheduler movement
to move a task out of a CPU, it should return non-zero in every case
when the task has been migrated out of the src_cpu.
> > /* Affinity changed (again). */
> > if (!cpu_isset(dest_cpu, p->cpus_allowed))
> > goto out;
> >
> > on_rq = p->se.on_rq;
> > +#ifdef CONFIG_PREEMPT
> > + if (!on_rq && task_thread_info(p)->migrate_count)
> > + goto out;
> > +#endif
>
> This means that move_task_off_dead_cpu() will spin until the task will be scheduled
> on the dead CPU. Given that we hold tasklist_lock and irqs are disabled, this may
> never happen.
>
Yes. My idea to fix this issue is the following:
If a thread has non zero migrate_count, we should still move it to a
different CPU upon hotplug cpu removal, even if this thread resists
migration. Care should be taken to send _all_ such threads to the _same_
CPU so they don't race for the per-cpu ressources. Does it make sense ?
We would have to keep the CPU affinity of the threads running on the
wrong CPU until they end their migrate disabled section, so that we can
put them back on their original CPU if it goes back online, otherwise we
could end up with concurrent per-cpu variables accesses.
(I'll wait for reply before coding a solution for this CPU HOTPLUG
related problem)
> (This patch adds a lot of #ifdef's, I think it could be simplified if you add
> get_migrate_count() which is defined as 0 when !CONFIG_PREEMPT).
Sure. Added migrate_count() and task_migrate_count(task).
>
> > @@ -4891,10 +4957,22 @@
> > list_del_init(head->next);
> >
> > spin_unlock(&rq->lock);
> > - __migrate_task(req->task, cpu, req->dest_cpu);
> > + migrated = __migrate_task(req->task, cpu, req->dest_cpu);
> > local_irq_enable();
> > -
> > - complete(&req->done);
> > + if (!migrated) {
> > + /*
> > + * If the process has not been migrated, let it run
> > + * until it reaches a migration_check() so it can
> > + * wake us up.
> > + */
> > + spin_lock_irq(&rq->lock);
> > + head = &rq->migration_queue;
> > + list_add(&req->list, head);
> > + set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
> > + spin_unlock_irq(&rq->lock);
> > + wake_up_process(req->task);
> > + } else
> > + complete(&req->done);
>
> I guess this is migration_thread(). The wake_up_process(req->task) looks strange,
> why? It can't help if the task waits for the event/mutex.
>
Hrm, the idea was to wake up the thread that is in the migrate disabled
section, which is what I seem to do req->task points to the process we
try to migrate. We poke it like this until is ends its critical
section. At that moment, the thread will wake up the migration thread,
and only then do we let sched_migrate_task, which is waiting for
completion, finish.
> And this is racy. What if check_migrate() is in progress, and the task has already
> checked TIF_NEED_MIGRATE?
>
The idea is to take the rq->lock to make sure the thread is not running
when we do this. Since the runqueue lock is released between the tests
in __migrate_task and this code, I should test again to see if it is
running. Currently, the migration thread retries actively if the thread
we are trying to migrate is in its critical section. The change I am
about to do does 2 things:
If the thread is on the runqueue, retry actively.
If the thread is not on the runqueue, set the NEED MIGRATE flag and go
to sleep, waiting for it to wake us up.
> Hm. We re-add "req" to rq->migration_queue. This means that migration_thread() will
> do a busy-wait loop. Not good and deadlockable, migration/X is SCHED_FIFO.
Yup. The comment above should hopefully fix it.
> And what if __migrate_task() failed because ->cpus_allowed was changed in between?
>
Right, we should check for this. Will fix.
Thanks for the thorough review.
Mathieu
> Oleg.
>
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [RFC] Thread Migration Preemption - v2
2007-07-14 18:27 ` Mathieu Desnoyers
@ 2007-07-14 19:56 ` Oleg Nesterov
0 siblings, 0 replies; 16+ messages in thread
From: Oleg Nesterov @ 2007-07-14 19:56 UTC (permalink / raw)
To: Mathieu Desnoyers; +Cc: linux-kernel, Ingo Molnar, Steven Rostedt
On 07/14, Mathieu Desnoyers wrote:
>
> * Oleg Nesterov (oleg@tv-sign.ru) wrote:
> > > /* Affinity changed (again). */
> > > if (!cpu_isset(dest_cpu, p->cpus_allowed))
> > > goto out;
> > >
> > > on_rq = p->se.on_rq;
> > > +#ifdef CONFIG_PREEMPT
> > > + if (!on_rq && task_thread_info(p)->migrate_count)
> > > + goto out;
> > > +#endif
> >
> > This means that move_task_off_dead_cpu() will spin until the task will be scheduled
> > on the dead CPU. Given that we hold tasklist_lock and irqs are disabled, this may
> > never happen.
> >
>
> Yes. My idea to fix this issue is the following:
>
> If a thread has non zero migrate_count, we should still move it to a
> different CPU upon hotplug cpu removal, even if this thread resists
> migration. Care should be taken to send _all_ such threads to the _same_
> CPU so they don't race for the per-cpu ressources. Does it make sense ?
>
> We would have to keep the CPU affinity of the threads running on the
> wrong CPU until they end their migrate disabled section, so that we can
> put them back on their original CPU if it goes back online, otherwise we
> could end up with concurrent per-cpu variables accesses.
Well, this means that migrate_disable() doesn't guarantee a stable
smp_processor_id(), not good.
> > > @@ -4891,10 +4957,22 @@
> > > list_del_init(head->next);
> > >
> > > spin_unlock(&rq->lock);
> > > - __migrate_task(req->task, cpu, req->dest_cpu);
> > > + migrated = __migrate_task(req->task, cpu, req->dest_cpu);
> > > local_irq_enable();
> > > -
> > > - complete(&req->done);
> > > + if (!migrated) {
> > > + /*
> > > + * If the process has not been migrated, let it run
> > > + * until it reaches a migration_check() so it can
> > > + * wake us up.
> > > + */
> > > + spin_lock_irq(&rq->lock);
> > > + head = &rq->migration_queue;
> > > + list_add(&req->list, head);
> > > + set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
> > > + spin_unlock_irq(&rq->lock);
> > > + wake_up_process(req->task);
> > > + } else
> > > + complete(&req->done);
> >
> > I guess this is migration_thread(). The wake_up_process(req->task) looks strange,
> > why? It can't help if the task waits for the event/mutex.
> >
>
> Hrm, the idea was to wake up the thread that is in the migrate disabled
> section, which is what I seem to do req->task points to the process we
> try to migrate. We poke it like this until is ends its critical
> section.
But this can only waste CPU, nothing more, no? Suppose that req->thread
sleeps waiting for the mutex. You can wake it up, and it will call schedule()
again.
This can help if req->thread does something like schedule_timeout(), but
I don't think this is a common case.
Oleg.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [RFC] Thread Migration Preemption - v3
2007-07-11 16:36 ` Oleg Nesterov
2007-07-14 18:27 ` Mathieu Desnoyers
@ 2007-07-14 18:40 ` Mathieu Desnoyers
2007-07-14 18:42 ` [RFC] Thread Migration Preemption - v4 Mathieu Desnoyers
2 siblings, 0 replies; 16+ messages in thread
From: Mathieu Desnoyers @ 2007-07-14 18:40 UTC (permalink / raw)
To: Oleg Nesterov; +Cc: linux-kernel, Ingo Molnar, Steven Rostedt
Thread Migration Preemption
This patch adds the ability to protect critical sections from migration to
another CPU without disabling preemption.
This will be useful to minimize the amount of preemption disabling for the -rt
patch. It will help leveraging improvements brought by the local_t types in
asm/local.h (see Documentation/local_ops.txt). Note that the updates done to
variables protected by migrate_disable must be either atomic or protected from
concurrent updates done by other threads.
Typical use:
migrate_disable();
local_inc(&__get_cpu_var(&my_local_t_var));
migrate_enable();
Which will increment the variable atomically wrt the local CPU.
Changes:
Do a check_migrate() upon migrate_enable() to answer to the migration
thread waiting for us to exit the migration disabled critical section. Use a
NEED_MIGRATE thread flag for this.
Note: (or we could say FIXME)
Is we ever want to check migration pending in assembly code, we will have to
make sure we test the right thread flag bits on each architectures. Care should
also be taken to check that the thread flags used won't trigger false positives
in non selective asm thread flag checks.
FIXME (HOTPLUG) :
> > /* Affinity changed (again). */
> > if (!cpu_isset(dest_cpu, p->cpus_allowed))
> > goto out;
> >
> > on_rq = p->se.on_rq;
> > +#ifdef CONFIG_PREEMPT
> > + if (!on_rq && task_thread_info(p)->migrate_count)
> > + goto out;
> > +#endif
>
> This means that move_task_off_dead_cpu() will spin until the task will be
> scheduled
> on the dead CPU. Given that we hold tasklist_lock and irqs are disabled, this
> may
> never happen.
>
Yes. My idea to fix this issue is the following:
If a thread has non zero migrate_count, we should still move it to a
different CPU upon hotplug cpu removal, even if this thread resists
migration. Care should be taken to send _all_ such threads to the _same_
CPU so they don't race for the per-cpu ressources. Does it make sense ?
We would have to keep the CPU affinity of the threads running on the
wrong CPU until they end their migrate disabled section, so that we can
put them back on their original CPU if it goes back online, otherwise we
could end up with concurrent per-cpu variables accesses.
(I'll wait for reply before coding a solution for this CPU HOTPLUG
related problem)
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
include/asm-alpha/thread_info.h | 3 +
include/asm-arm/thread_info.h | 5 +
include/asm-arm26/thread_info.h | 5 +
include/asm-avr32/thread_info.h | 4 +
include/asm-blackfin/thread_info.h | 4 +
include/asm-cris/thread_info.h | 4 +
include/asm-frv/thread_info.h | 4 +
include/asm-h8300/thread_info.h | 4 +
include/asm-i386/thread_info.h | 6 +-
include/asm-ia64/thread_info.h | 4 +
include/asm-m32r/thread_info.h | 4 +
include/asm-m68k/thread_info.h | 2
include/asm-m68knommu/thread_info.h | 3 +
include/asm-mips/thread_info.h | 4 +
include/asm-parisc/thread_info.h | 4 +
include/asm-powerpc/thread_info.h | 4 +
include/asm-s390/thread_info.h | 4 +
include/asm-sh/thread_info.h | 4 +
include/asm-sh64/thread_info.h | 4 +
include/asm-sparc/thread_info.h | 4 +
include/asm-sparc64/thread_info.h | 5 +
include/asm-um/thread_info.h | 4 +
include/asm-v850/thread_info.h | 4 +
include/asm-x86_64/thread_info.h | 4 +
include/asm-xtensa/thread_info.h | 4 +
include/linux/preempt.h | 47 ++++++++++++++++-
kernel/sched.c | 98 +++++++++++++++++++++++++++++++++---
lib/smp_processor_id.c | 6 +-
28 files changed, 240 insertions(+), 12 deletions(-)
Index: linux-2.6-lttng/include/asm-i386/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-i386/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-i386/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -31,8 +31,7 @@ struct thread_info {
unsigned long status; /* thread-synchronous flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
-
-
+ int migrate_count;/* 0: can migrate, <0: BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thead
0-0xFFFFFFFF for kernel-thread
@@ -74,6 +73,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -132,6 +132,7 @@ static inline struct thread_info *curren
#define TIF_SYSCALL_AUDIT 6 /* syscall auditing active */
#define TIF_SECCOMP 7 /* secure computing */
#define TIF_RESTORE_SIGMASK 8 /* restore signal mask in do_signal() */
+#define TIF_NEED_MIGRATE 9 /* migration necessary */
#define TIF_MEMDIE 16
#define TIF_DEBUG 17 /* uses debug registers */
#define TIF_IO_BITMAP 18 /* uses I/O bitmap */
@@ -147,6 +148,7 @@ static inline struct thread_info *curren
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_DEBUG (1<<TIF_DEBUG)
#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
#define _TIF_FREEZE (1<<TIF_FREEZE)
Index: linux-2.6-lttng/include/linux/preempt.h
===================================================================
--- linux-2.6-lttng.orig/include/linux/preempt.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/linux/preempt.h 2007-07-14 13:45:10.000000000 -0400
@@ -12,15 +12,22 @@
#ifdef CONFIG_DEBUG_PREEMPT
extern void fastcall add_preempt_count(int val);
extern void fastcall sub_preempt_count(int val);
+ extern void fastcall add_migrate_count(int val);
+ extern void fastcall sub_migrate_count(int val);
#else
# define add_preempt_count(val) do { preempt_count() += (val); } while (0)
# define sub_preempt_count(val) do { preempt_count() -= (val); } while (0)
+# define add_migrate_count(val) do { migrate_count() += (val); } while (0)
+# define sub_migrate_count(val) do { migrate_count() -= (val); } while (0)
#endif
#define inc_preempt_count() add_preempt_count(1)
#define dec_preempt_count() sub_preempt_count(1)
-#define preempt_count() (current_thread_info()->preempt_count)
+#define preempt_count() (current_thread_info()->preempt_count)
+
+#define inc_migrate_count() add_migrate_count(1)
+#define dec_migrate_count() sub_migrate_count(1)
#ifdef CONFIG_PREEMPT
@@ -51,6 +58,38 @@ do { \
preempt_check_resched(); \
} while (0)
+#define migrate_count() (current_thread_info()->migrate_count)
+#define task_migrate_count(task) (task_thread_info(task)->migrate_count)
+
+#define migrate_disable() \
+do { \
+ inc_migrate_count(); \
+ barrier(); \
+} while (0)
+
+#define migrate_enable_no_check() \
+do { \
+ barrier(); \
+ dec_migrate_count(); \
+} while (0)
+
+#ifdef CONFIG_SMP
+#define check_migrate() \
+do { \
+ if (unlikely(test_thread_flag(TIF_NEED_MIGRATE))) \
+ do_check_migrate(); \
+} while (0)
+#else
+#define check_migrate()
+#endif
+
+#define migrate_enable() \
+do { \
+ migrate_enable_no_check(); \
+ barrier(); \
+ check_migrate(); \
+} while (0)
+
#else
#define preempt_disable() do { } while (0)
@@ -58,6 +97,12 @@ do { \
#define preempt_enable() do { } while (0)
#define preempt_check_resched() do { } while (0)
+#define migrate_count() 0
+#define task_migrate_count(task) 0
+
+#define migrate_disable() do { } while (0)
+#define migrate_enable() do { } while (0)
+
#endif
#endif /* __LINUX_PREEMPT_H */
Index: linux-2.6-lttng/kernel/sched.c
===================================================================
--- linux-2.6-lttng.orig/kernel/sched.c 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/kernel/sched.c 2007-07-14 14:18:07.000000000 -0400
@@ -946,7 +946,7 @@ migrate_task(struct task_struct *p, int
* If the task is not on a runqueue (and not running), then
* it is sufficient to simply update the task's cpu field.
*/
- if (!p->se.on_rq && !task_running(rq, p)) {
+ if (!p->se.on_rq && !task_running(rq, p) && !task_migrate_count(p)) {
set_task_cpu(p, dest_cpu);
return 0;
}
@@ -1347,7 +1347,8 @@ static int try_to_wake_up(struct task_st
#ifdef CONFIG_SMP
if (unlikely(task_running(rq, p)))
goto out_activate;
-
+ if (task_migrate_count(p))
+ goto out_activate;
new_cpu = cpu;
schedstat_inc(rq, ttwu_cnt);
@@ -1534,6 +1535,7 @@ void sched_fork(struct task_struct *p, i
#ifdef CONFIG_PREEMPT
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = 1;
+ task_thread_info(p)->migrate_count = 0;
#endif
put_cpu();
}
@@ -1933,6 +1935,8 @@ static void sched_migrate_task(struct ta
if (!cpu_isset(dest_cpu, p->cpus_allowed)
|| unlikely(cpu_is_offline(dest_cpu)))
goto out;
+ if (task_migrate_count(p))
+ goto out;
trace_mark(kernel_sched_migrate_task, "%d %ld %d",
p->pid, p->state, dest_cpu);
@@ -1996,6 +2000,7 @@ int can_migrate_task(struct task_struct
* 1) running (obviously), or
* 2) cannot be migrated to this CPU due to cpus_allowed, or
* 3) are cache-hot on their current CPU.
+ * 4) migration preemption is non 0 for this non running task.
*/
if (!cpu_isset(this_cpu, p->cpus_allowed))
return 0;
@@ -2003,6 +2008,8 @@ int can_migrate_task(struct task_struct
if (task_running(rq, p))
return 0;
+ if (task_migrate_count(p))
+ return 0;
/*
* Aggressive migration if too many balance attempts have failed:
@@ -3220,6 +3227,29 @@ void fastcall sub_preempt_count(int val)
}
EXPORT_SYMBOL(sub_preempt_count);
+void fastcall add_migrate_count(int val)
+{
+ /*
+ * Underflow?
+ */
+ if (DEBUG_LOCKS_WARN_ON((migrate_count() < 0)))
+ return;
+ migrate_count() += val;
+}
+EXPORT_SYMBOL(add_migrate_count);
+
+void fastcall sub_migrate_count(int val)
+{
+ /*
+ * Underflow?
+ */
+ if (DEBUG_LOCKS_WARN_ON(val > migrate_count()))
+ return;
+
+ migrate_count() -= val;
+}
+EXPORT_SYMBOL(sub_migrate_count);
+
#endif
/*
@@ -3353,6 +3383,28 @@ need_resched_nonpreemptible:
EXPORT_SYMBOL(schedule);
#ifdef CONFIG_PREEMPT
+
+#ifdef CONFIG_SMP
+/*
+ * Wake up the migration thread to deal with our pending migration.
+ * If we have been moved since, we will just wake up the migration thread from
+ * the wrong CPU, which does not hurt anyone. (that's why we use
+ * raw_smp_processor_id()).
+ */
+void __sched do_check_migrate(void)
+{
+ struct rq *rq;
+
+ if (migrate_count())
+ return;
+
+ clear_thread_flag(TIF_NEED_MIGRATE);
+ rq = cpu_rq(raw_smp_processor_id());
+ wake_up_process(rq->migration_thread);
+}
+EXPORT_SYMBOL(do_check_migrate);
+#endif
+
/*
* this is the entry point to schedule() from in-kernel preemption
* off of preempt_enable. Kernel preemptions off return from interrupt
@@ -4814,7 +4866,7 @@ EXPORT_SYMBOL_GPL(set_cpus_allowed);
* So we race with normal scheduler movements, but that's OK, as long
* as the task is no longer on this CPU.
*
- * Returns non-zero if task was successfully migrated.
+ * Returns non-zero if task is not on src_cpu when this function ends.
*/
static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
@@ -4829,13 +4881,17 @@ static int __migrate_task(struct task_st
double_rq_lock(rq_src, rq_dest);
/* Already moved. */
- if (task_cpu(p) != src_cpu)
+ if (task_cpu(p) != src_cpu) {
+ ret = 1;
goto out;
+ }
/* Affinity changed (again). */
if (!cpu_isset(dest_cpu, p->cpus_allowed))
goto out;
on_rq = p->se.on_rq;
+ if (!on_rq && task_migrate_count(p))
+ goto out;
if (on_rq)
deactivate_task(rq_src, p, 0);
set_task_cpu(p, dest_cpu);
@@ -4858,6 +4914,7 @@ static int migration_thread(void *data)
{
int cpu = (long)data;
struct rq *rq;
+ int migrated;
rq = cpu_rq(cpu);
BUG_ON(rq->migration_thread != current);
@@ -4891,10 +4948,37 @@ static int migration_thread(void *data)
list_del_init(head->next);
spin_unlock(&rq->lock);
- __migrate_task(req->task, cpu, req->dest_cpu);
+ migrated = __migrate_task(req->task, cpu, req->dest_cpu);
local_irq_enable();
-
- complete(&req->done);
+ if (!migrated) {
+ /*
+ * If the process has not been migrated, let it run
+ * until it reaches a migration_check() so it can
+ * wake us up.
+ */
+ spin_lock_irq(&rq->lock);
+ head = &rq->migration_queue;
+ list_add(&req->list, head);
+ if (p->se.on_rq) {
+ /*
+ * The process is on the runqueue, it could
+ * exit its critical section at any moment,
+ * don't race with it and retry actively.
+ */
+ spin_unlock_irq(&rq->lock);
+ continue;
+ }
+ set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
+ set_current_state(TASK_INTERRUPTIBLE);
+ spin_unlock_irq(&rq->lock);
+ /*
+ * Wait for the process currently in its critical
+ * section.
+ */
+ wake_up_process(req->task);
+ schedule();
+ } else
+ complete(&req->done);
}
__set_current_state(TASK_RUNNING);
return 0;
Index: linux-2.6-lttng/include/asm-alpha/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-alpha/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-alpha/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -21,6 +21,7 @@ struct thread_info {
mm_segment_t addr_limit; /* thread address space */
unsigned cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
int bpt_nsaved;
unsigned long bpt_addr[2]; /* breakpoint handling */
@@ -77,6 +78,7 @@ register struct thread_info *__current_t
#define TIF_MEMDIE 8
#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal */
#define TIF_SYSCALL_AUDIT 10
+#define TIF_NEED_MIGRATE 11 /* migration necessary */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
@@ -84,6 +86,7 @@ register struct thread_info *__current_t
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
/* Work to do on interrupt/exception return. */
#define _TIF_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED)
Index: linux-2.6-lttng/include/asm-arm/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-arm/thread_info.h 2007-07-14 13:20:10.000000000 -0400
+++ linux-2.6-lttng/include/asm-arm/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -51,6 +51,7 @@ struct cpu_context_save {
struct thread_info {
unsigned long flags; /* low level flags */
int preempt_count; /* 0 => preemptable, <0 => bug */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* address limit */
struct task_struct *task; /* main task structure */
struct exec_domain *exec_domain; /* execution domain */
@@ -72,6 +73,7 @@ struct thread_info {
.exec_domain = &default_exec_domain, \
.flags = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.cpu_domain = domain_val(DOMAIN_USER, DOMAIN_MANAGER) | \
domain_val(DOMAIN_KERNEL, DOMAIN_MANAGER) | \
@@ -137,12 +139,14 @@ extern void iwmmxt_task_switch(struct th
* TIF_SYSCALL_TRACE - syscall trace active
* TIF_SIGPENDING - signal pending
* TIF_NEED_RESCHED - rescheduling necessary
+ * TIF_NEED_MIGRATE - migration necessary
* TIF_USEDFPU - FPU was used by this task this quantum (SMP)
* TIF_POLLING_NRFLAG - true if poll_idle() is polling TIF_NEED_RESCHED
* TIF_SYSCALL_AUDIT - Syscall audting active - LTTng
*/
#define TIF_SIGPENDING 0
#define TIF_NEED_RESCHED 1
+#define TIF_NEED_MIGRATE 2
#define TIF_SYSCALL_AUDIT 7
#define TIF_SYSCALL_TRACE 8
#define TIF_POLLING_NRFLAG 16
@@ -152,6 +156,7 @@ extern void iwmmxt_task_switch(struct th
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-arm26/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-arm26/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-arm26/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -45,6 +45,7 @@ struct cpu_context_save {
struct thread_info {
unsigned long flags; /* low level flags */
int preempt_count; /* 0 => preemptable, <0 => bug */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* address limit */
struct task_struct *task; /* main task structure */
struct exec_domain *exec_domain; /* execution domain */
@@ -60,6 +61,7 @@ struct thread_info {
.exec_domain &default_exec_domain, \
.flags 0, \
.preempt_count 0, \
+ .migrate_count 0, \
.addr_limit KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -112,11 +114,13 @@ extern void free_thread_info(struct thre
* TIF_SYSCALL_TRACE - syscall trace active
* TIF_SIGPENDING - signal pending
* TIF_NEED_RESCHED - rescheduling necessary
+ * TIF_NEED_MIGRATE - migration necessary
* TIF_USEDFPU - FPU was used by this task this quantum (SMP)
* TIF_POLLING_NRFLAG - true if poll_idle() is polling TIF_NEED_RESCHED
*/
#define TIF_SIGPENDING 0
#define TIF_NEED_RESCHED 1
+#define TIF_NEED_MIGRATE 2
#define TIF_SYSCALL_TRACE 8
#define TIF_USED_FPU 16
#define TIF_POLLING_NRFLAG 17
@@ -124,6 +128,7 @@ extern void free_thread_info(struct thre
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_USED_FPU (1 << TIF_USED_FPU)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-avr32/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-avr32/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-avr32/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -25,6 +25,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
__u32 cpu;
__s32 preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
__u8 supervisor_stack[0];
};
@@ -36,6 +37,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall \
} \
@@ -83,6 +85,7 @@ static inline struct thread_info *curren
#define TIF_MEMDIE 6
#define TIF_RESTORE_SIGMASK 7 /* restore signal mask in do_signal */
#define TIF_CPU_GOING_TO_SLEEP 8 /* CPU is entering sleep 0 mode */
+#define TIF_NEED_MIGRATE 9 /* migration necessary */
#define TIF_USERSPACE 31 /* true if FS sets userspace */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
@@ -94,6 +97,7 @@ static inline struct thread_info *curren
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_CPU_GOING_TO_SLEEP (1 << TIF_CPU_GOING_TO_SLEEP)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
/* XXX: These two masks must never span more than 16 bits! */
/* work to do on interrupt/exception return */
Index: linux-2.6-lttng/include/asm-blackfin/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-blackfin/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-blackfin/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -54,6 +54,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* address limit */
struct restart_block restart_block;
struct l1_scratch_task_info l1_task_info;
@@ -69,6 +70,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -125,6 +127,7 @@ static inline struct thread_info *curren
#define TIF_MEMDIE 4
#define TIF_RESTORE_SIGMASK 5 /* restore signal mask in do_signal() */
#define TIF_FREEZE 6 /* is freezing for suspend */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -133,6 +136,7 @@ static inline struct thread_info *curren
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_FREEZE (1<<TIF_FREEZE)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
Index: linux-2.6-lttng/include/asm-cris/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-cris/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-cris/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -32,6 +32,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thead
@@ -58,6 +59,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -81,6 +83,7 @@ struct thread_info {
#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
#define TIF_SIGPENDING 1 /* signal pending */
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
+#define TIF_NEED_MIGRATE 3 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17
@@ -88,6 +91,7 @@ struct thread_info {
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
#define _TIF_ALLWORK_MASK 0x0000FFFF /* work to do on any return to u-space */
Index: linux-2.6-lttng/include/asm-frv/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-frv/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-frv/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -36,6 +36,7 @@ struct thread_info {
unsigned long status; /* thread-synchronous flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thead
@@ -68,6 +69,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -113,6 +115,7 @@ register struct thread_info *__current_t
#define TIF_SINGLESTEP 3 /* restore singlestep on return to user mode */
#define TIF_IRET 4 /* return with iret */
#define TIF_RESTORE_SIGMASK 5 /* restore signal mask in do_signal() */
+#define TIF_NEED_MIGRATE 6 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17 /* OOM killer killed process */
#define TIF_FREEZE 18 /* freezing for suspend */
@@ -125,6 +128,7 @@ register struct thread_info *__current_t
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_FREEZE (1 << TIF_FREEZE)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
#define _TIF_ALLWORK_MASK 0x0000FFFF /* work to do on any return to u-space */
Index: linux-2.6-lttng/include/asm-h8300/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-h8300/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-h8300/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -24,6 +24,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -37,6 +38,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -91,12 +93,14 @@ static inline struct thread_info *curren
#define TIF_POLLING_NRFLAG 3 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 4
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
Index: linux-2.6-lttng/include/asm-ia64/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-ia64/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-ia64/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -30,6 +30,7 @@ struct thread_info {
__u32 status; /* Thread synchronous flags */
mm_segment_t addr_limit; /* user-level address space limit */
int preempt_count; /* 0=premptable, <0=BUG; will also serve as bh-counter */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -43,6 +44,7 @@ struct thread_info {
.cpu = 0, \
.addr_limit = KERNEL_DS, \
.preempt_count = 0, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -86,6 +88,7 @@ struct thread_info {
#define TIF_SINGLESTEP 4 /* restore singlestep on return to user mode */
#define TIF_RESTORE_SIGMASK 5 /* restore signal mask in do_signal() */
#define TIF_PERFMON_WORK 6 /* work for pfm_handle_work() */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17
#define TIF_MCA_INIT 18 /* this task is processing MCA or INIT */
@@ -98,6 +101,7 @@ struct thread_info {
#define _TIF_SYSCALL_TRACEAUDIT (_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_PERFMON_WORK (1 << TIF_PERFMON_WORK)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-m32r/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-m32r/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-m32r/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -29,6 +29,7 @@ struct thread_info {
unsigned long status; /* thread-synchronous flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thread
@@ -69,6 +70,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -150,6 +152,7 @@ static inline unsigned int get_thread_fa
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
#define TIF_SINGLESTEP 3 /* restore singlestep on return to user mode */
#define TIF_IRET 4 /* return with iret */
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
/* 31..28 fault code */
#define TIF_MEMDIE 17
@@ -160,6 +163,7 @@ static inline unsigned int get_thread_fa
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_IRET (1<<TIF_IRET)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
#define _TIF_ALLWORK_MASK 0x0000FFFF /* work to do on any return to u-space */
Index: linux-2.6-lttng/include/asm-m68k/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-m68k/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-m68k/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -9,6 +9,7 @@ struct thread_info {
unsigned long flags;
struct exec_domain *exec_domain; /* execution domain */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
__u32 cpu; /* should always be 0 on m68k */
struct restart_block restart_block;
};
@@ -59,5 +60,6 @@ struct thread_info {
#define TIF_DELAYED_TRACE 14 /* single step a syscall */
#define TIF_SYSCALL_TRACE 15 /* syscall trace active */
#define TIF_MEMDIE 16
+#define TIF_NEED_MIGRATE 17 /* migration necessary */
#endif /* _ASM_M68K_THREAD_INFO_H */
Index: linux-2.6-lttng/include/asm-m68knommu/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-m68knommu/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-m68knommu/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -37,6 +37,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -88,6 +89,7 @@ static inline struct thread_info *curren
#define TIF_POLLING_NRFLAG 3 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 4
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
/* as above, but as bit values */
@@ -96,6 +98,7 @@ static inline struct thread_info *curren
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_MEMDIE (1<<TIF_MEMDIE)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
Index: linux-2.6-lttng/include/asm-mips/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-mips/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-mips/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -28,6 +28,7 @@ struct thread_info {
unsigned long tp_value; /* thread pointer */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thead
@@ -49,6 +50,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -113,6 +115,7 @@ register struct thread_info *__current_t
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
#define TIF_SYSCALL_AUDIT 3 /* syscall auditing active */
#define TIF_SECCOMP 4 /* secure computing */
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal() */
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling TIF_NEED_RESCHED */
@@ -125,6 +128,7 @@ register struct thread_info *__current_t
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_USEDFPU (1<<TIF_USEDFPU)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-parisc/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-parisc/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-parisc/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -13,6 +13,7 @@ struct thread_info {
mm_segment_t addr_limit; /* user-level address space limit */
__u32 cpu; /* current CPU */
int preempt_count; /* 0=premptable, <0=BUG; will also serve as bh-counter */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -24,6 +25,7 @@ struct thread_info {
.cpu = 0, \
.addr_limit = KERNEL_DS, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall \
} \
@@ -62,6 +64,7 @@ struct thread_info {
#define TIF_32BIT 4 /* 32 bit binary */
#define TIF_MEMDIE 5
#define TIF_RESTORE_SIGMASK 6 /* restore saved signal mask */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
@@ -69,6 +72,7 @@ struct thread_info {
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_32BIT (1 << TIF_32BIT)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | \
_TIF_NEED_RESCHED | _TIF_RESTORE_SIGMASK)
Index: linux-2.6-lttng/include/asm-powerpc/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-powerpc/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-powerpc/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -35,6 +35,7 @@ struct thread_info {
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
unsigned long local_flags; /* private flags for thread */
@@ -53,6 +54,7 @@ struct thread_info {
.exec_domain = &default_exec_domain, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -124,6 +126,7 @@ static inline struct thread_info *curren
#define TIF_FREEZE 14 /* Freezing for suspend */
#define TIF_RUNLATCH 15 /* Is the runlatch enabled? */
#define TIF_ABI_PENDING 16 /* 32/64 bit switch needed */
+#define TIF_NEED_MIGRATE 17 /* migration necessary */
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -142,6 +145,7 @@ static inline struct thread_info *curren
#define _TIF_FREEZE (1<<TIF_FREEZE)
#define _TIF_RUNLATCH (1<<TIF_RUNLATCH)
#define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_SYSCALL_T_OR_A (_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP)
#define _TIF_USER_WORK_MASK ( _TIF_SIGPENDING | \
Index: linux-2.6-lttng/include/asm-s390/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-s390/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-s390/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -51,6 +51,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
unsigned int cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -64,6 +65,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -96,6 +98,7 @@ static inline struct thread_info *curren
#define TIF_SYSCALL_AUDIT 5 /* syscall auditing active */
#define TIF_SINGLE_STEP 6 /* deliver sigtrap on return to user */
#define TIF_MCCK_PENDING 7 /* machine check handling is pending */
+#define TIF_NEED_MIGRATE 8 /* migration necessary */
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
@@ -110,6 +113,7 @@ static inline struct thread_info *curren
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SINGLE_STEP (1<<TIF_SINGLE_STEP)
#define _TIF_MCCK_PENDING (1<<TIF_MCCK_PENDING)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_USEDFPU (1<<TIF_USEDFPU)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_31BIT (1<<TIF_31BIT)
Index: linux-2.6-lttng/include/asm-sh/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-sh/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-sh/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -21,6 +21,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
__u32 cpu;
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space */
struct restart_block restart_block;
unsigned long previous_sp; /* sp of previous stack in case
@@ -58,6 +59,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -112,6 +114,7 @@ static inline struct thread_info *curren
#define TIF_RESTORE_SIGMASK 3 /* restore signal mask in do_signal() */
#define TIF_SINGLESTEP 4 /* singlestepping active */
#define TIF_SYSCALL_AUDIT 6 /* syscall audit active */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 18
@@ -123,6 +126,7 @@ static inline struct thread_info *curren
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_USEDFPU (1<<TIF_USEDFPU)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_FREEZE (1<<TIF_FREEZE)
Index: linux-2.6-lttng/include/asm-sh64/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-sh64/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-sh64/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -23,6 +23,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
/* Put the 4 32-bit fields together to make asm offsetting easier. */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
__u16 cpu;
mm_segment_t addr_limit;
@@ -41,6 +42,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -80,12 +82,14 @@ static inline struct thread_info *curren
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_MEMDIE 4
#define TIF_RESTORE_SIGMASK 5 /* Restore signal mask in do_signal */
+#define TIF_NEED_MIGRATE 6 /* migration necessary */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#endif /* __KERNEL__ */
Index: linux-2.6-lttng/include/asm-sparc/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-sparc/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-sparc/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -33,6 +33,7 @@ struct thread_info {
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
int softirq_count;
int hardirq_count;
@@ -65,6 +66,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -132,6 +134,7 @@ BTFIXUPDEF_CALL(void, free_thread_info,
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
#define TIF_USEDFPU 8 /* FPU was used by this task
* this quantum (SMP) */
#define TIF_POLLING_NRFLAG 9 /* true if poll_idle() is polling
@@ -144,6 +147,7 @@ BTFIXUPDEF_CALL(void, free_thread_info,
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_USEDFPU (1<<TIF_USEDFPU)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-sparc64/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-sparc64/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-sparc64/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -47,6 +47,7 @@ struct thread_info {
struct pt_regs *kregs;
struct exec_domain *exec_domain;
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
__u8 new_child;
__u8 syscall_noerror;
__u16 cpu;
@@ -137,6 +138,7 @@ struct thread_info {
.flags = ((unsigned long)ASI_P) << TI_FLAG_CURRENT_DS_SHIFT, \
.exec_domain = &default_exec_domain, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -225,7 +227,7 @@ register struct thread_info *current_thr
#define TIF_UNALIGNED 5 /* allowed to do unaligned accesses */
#define TIF_NEWSIGNALS 6 /* wants new-style signals */
#define TIF_32BIT 7 /* 32-bit binary */
-/* flag bit 8 is available */
+#define TIF_NEED_MIGRATE 8 /* migration necessary */
#define TIF_SECCOMP 9 /* secure computing */
#define TIF_SYSCALL_AUDIT 10 /* syscall auditing active */
/* flag bit 11 is available */
@@ -244,6 +246,7 @@ register struct thread_info *current_thr
#define _TIF_UNALIGNED (1<<TIF_UNALIGNED)
#define _TIF_NEWSIGNALS (1<<TIF_NEWSIGNALS)
#define _TIF_32BIT (1<<TIF_32BIT)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
Index: linux-2.6-lttng/include/asm-um/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-um/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-um/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -18,6 +18,7 @@ struct thread_info {
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user
0-0xFFFFFFFF for kernel */
@@ -32,6 +33,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -82,6 +84,7 @@ static inline struct thread_info *curren
#define TIF_MEMDIE 5
#define TIF_SYSCALL_AUDIT 6
#define TIF_RESTORE_SIGMASK 7
+#define TIF_NEED_MIGRATE 8 /* migration necessary */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
@@ -90,5 +93,6 @@ static inline struct thread_info *curren
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#endif
Index: linux-2.6-lttng/include/asm-v850/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-v850/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-v850/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -32,6 +32,7 @@ struct thread_info {
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -42,6 +43,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -82,12 +84,14 @@ struct thread_info {
#define TIF_POLLING_NRFLAG 3 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 4
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
/* Size of kernel stack for each process. */
Index: linux-2.6-lttng/include/asm-x86_64/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-x86_64/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-x86_64/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -30,6 +30,7 @@ struct thread_info {
__u32 status; /* thread synchronous flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit;
struct restart_block restart_block;
@@ -48,6 +49,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -115,6 +117,7 @@ static inline struct thread_info *stack_
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal */
#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */
+#define TIF_NEED_MIGRATE 11 /* migration necessary */
/* 16 free */
#define TIF_IA32 17 /* 32bit process */
#define TIF_FORK 18 /* ret_from_fork */
@@ -133,6 +136,7 @@ static inline struct thread_info *stack_
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_MCE_NOTIFY (1<<TIF_MCE_NOTIFY)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_IA32 (1<<TIF_IA32)
#define _TIF_FORK (1<<TIF_FORK)
#define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING)
Index: linux-2.6-lttng/include/asm-xtensa/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-xtensa/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-xtensa/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -34,6 +34,7 @@ struct thread_info {
unsigned long status; /* thread-synchronous flags */
__u32 cpu; /* current CPU */
__s32 preempt_count; /* 0 => preemptable,< 0 => BUG*/
+ __s32 migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space */
struct restart_block restart_block;
@@ -72,6 +73,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -116,6 +118,7 @@ static inline struct thread_info *curren
#define TIF_IRET 4 /* return with iret */
#define TIF_MEMDIE 5
#define TIF_RESTORE_SIGMASK 6 /* restore signal mask in do_signal() */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -123,6 +126,7 @@ static inline struct thread_info *curren
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_IRET (1<<TIF_IRET)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
Index: linux-2.6-lttng/lib/smp_processor_id.c
===================================================================
--- linux-2.6-lttng.orig/lib/smp_processor_id.c 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/lib/smp_processor_id.c 2007-07-14 13:20:12.000000000 -0400
@@ -10,12 +10,16 @@
unsigned int debug_smp_processor_id(void)
{
unsigned long preempt_count = preempt_count();
+ unsigned long migrate_count = migrate_count();
int this_cpu = raw_smp_processor_id();
cpumask_t this_mask;
if (likely(preempt_count))
goto out;
+ if (likely(migrate_count))
+ goto out;
+
if (irqs_disabled())
goto out;
@@ -42,7 +46,7 @@ unsigned int debug_smp_processor_id(void
if (!printk_ratelimit())
goto out_enable;
- printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] code: %s/%d\n", preempt_count(), current->comm, current->pid);
+ printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] migration [%08x] code: %s/%d\n", preempt_count(), migrate_count(), current->comm, current->pid);
print_symbol("caller is %s\n", (long)__builtin_return_address(0));
dump_stack();
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
^ permalink raw reply [flat|nested] 16+ messages in thread* [RFC] Thread Migration Preemption - v4
2007-07-11 16:36 ` Oleg Nesterov
2007-07-14 18:27 ` Mathieu Desnoyers
2007-07-14 18:40 ` [RFC] Thread Migration Preemption - v3 Mathieu Desnoyers
@ 2007-07-14 18:42 ` Mathieu Desnoyers
2007-07-14 19:14 ` Peter Zijlstra
` (2 more replies)
2 siblings, 3 replies; 16+ messages in thread
From: Mathieu Desnoyers @ 2007-07-14 18:42 UTC (permalink / raw)
To: Oleg Nesterov; +Cc: linux-kernel, Ingo Molnar, Steven Rostedt
Thread Migration Preemption
(v3 did not have the latest updates from Oleg review)
This patch adds the ability to protect critical sections from migration to
another CPU without disabling preemption.
This will be useful to minimize the amount of preemption disabling for the -rt
patch. It will help leveraging improvements brought by the local_t types in
asm/local.h (see Documentation/local_ops.txt). Note that the updates done to
variables protected by migrate_disable must be either atomic or protected from
concurrent updates done by other threads.
Typical use:
migrate_disable();
local_inc(&__get_cpu_var(&my_local_t_var));
migrate_enable();
Which will increment the variable atomically wrt the local CPU.
Changes:
Do a check_migrate() upon migrate_enable() to answer to the migration
thread waiting for us to exit the migration disabled critical section. Use a
NEED_MIGRATE thread flag for this.
Note: (or we could say FIXME)
Is we ever want to check migration pending in assembly code, we will have to
make sure we test the right thread flag bits on each architectures. Care should
also be taken to check that the thread flags used won't trigger false positives
in non selective asm thread flag checks.
FIXME (HOTPLUG) :
> > /* Affinity changed (again). */
> > if (!cpu_isset(dest_cpu, p->cpus_allowed))
> > goto out;
> >
> > on_rq = p->se.on_rq;
> > +#ifdef CONFIG_PREEMPT
> > + if (!on_rq && task_thread_info(p)->migrate_count)
> > + goto out;
> > +#endif
>
> This means that move_task_off_dead_cpu() will spin until the task will be
> scheduled
> on the dead CPU. Given that we hold tasklist_lock and irqs are disabled, this
> may
> never happen.
>
Yes. My idea to fix this issue is the following:
If a thread has non zero migrate_count, we should still move it to a
different CPU upon hotplug cpu removal, even if this thread resists
migration. Care should be taken to send _all_ such threads to the _same_
CPU so they don't race for the per-cpu ressources. Does it make sense ?
We would have to keep the CPU affinity of the threads running on the
wrong CPU until they end their migrate disabled section, so that we can
put them back on their original CPU if it goes back online, otherwise we
could end up with concurrent per-cpu variables accesses.
(I'll wait for reply before coding a solution for this CPU HOTPLUG
related problem)
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
include/asm-alpha/thread_info.h | 3 +
include/asm-arm/thread_info.h | 5 +
include/asm-arm26/thread_info.h | 5 +
include/asm-avr32/thread_info.h | 4 +
include/asm-blackfin/thread_info.h | 4 +
include/asm-cris/thread_info.h | 4 +
include/asm-frv/thread_info.h | 4 +
include/asm-h8300/thread_info.h | 4 +
include/asm-i386/thread_info.h | 6 +-
include/asm-ia64/thread_info.h | 4 +
include/asm-m32r/thread_info.h | 4 +
include/asm-m68k/thread_info.h | 2
include/asm-m68knommu/thread_info.h | 3 +
include/asm-mips/thread_info.h | 4 +
include/asm-parisc/thread_info.h | 4 +
include/asm-powerpc/thread_info.h | 4 +
include/asm-s390/thread_info.h | 4 +
include/asm-sh/thread_info.h | 4 +
include/asm-sh64/thread_info.h | 4 +
include/asm-sparc/thread_info.h | 4 +
include/asm-sparc64/thread_info.h | 5 +
include/asm-um/thread_info.h | 4 +
include/asm-v850/thread_info.h | 4 +
include/asm-x86_64/thread_info.h | 4 +
include/asm-xtensa/thread_info.h | 4 +
include/linux/preempt.h | 47 ++++++++++++++++
kernel/sched.c | 103 +++++++++++++++++++++++++++++++++---
lib/smp_processor_id.c | 6 +-
28 files changed, 245 insertions(+), 12 deletions(-)
Index: linux-2.6-lttng/include/asm-i386/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-i386/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-i386/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -31,8 +31,7 @@ struct thread_info {
unsigned long status; /* thread-synchronous flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
-
-
+ int migrate_count;/* 0: can migrate, <0: BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thead
0-0xFFFFFFFF for kernel-thread
@@ -74,6 +73,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -132,6 +132,7 @@ static inline struct thread_info *curren
#define TIF_SYSCALL_AUDIT 6 /* syscall auditing active */
#define TIF_SECCOMP 7 /* secure computing */
#define TIF_RESTORE_SIGMASK 8 /* restore signal mask in do_signal() */
+#define TIF_NEED_MIGRATE 9 /* migration necessary */
#define TIF_MEMDIE 16
#define TIF_DEBUG 17 /* uses debug registers */
#define TIF_IO_BITMAP 18 /* uses I/O bitmap */
@@ -147,6 +148,7 @@ static inline struct thread_info *curren
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_DEBUG (1<<TIF_DEBUG)
#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
#define _TIF_FREEZE (1<<TIF_FREEZE)
Index: linux-2.6-lttng/include/linux/preempt.h
===================================================================
--- linux-2.6-lttng.orig/include/linux/preempt.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/linux/preempt.h 2007-07-14 13:45:10.000000000 -0400
@@ -12,15 +12,22 @@
#ifdef CONFIG_DEBUG_PREEMPT
extern void fastcall add_preempt_count(int val);
extern void fastcall sub_preempt_count(int val);
+ extern void fastcall add_migrate_count(int val);
+ extern void fastcall sub_migrate_count(int val);
#else
# define add_preempt_count(val) do { preempt_count() += (val); } while (0)
# define sub_preempt_count(val) do { preempt_count() -= (val); } while (0)
+# define add_migrate_count(val) do { migrate_count() += (val); } while (0)
+# define sub_migrate_count(val) do { migrate_count() -= (val); } while (0)
#endif
#define inc_preempt_count() add_preempt_count(1)
#define dec_preempt_count() sub_preempt_count(1)
-#define preempt_count() (current_thread_info()->preempt_count)
+#define preempt_count() (current_thread_info()->preempt_count)
+
+#define inc_migrate_count() add_migrate_count(1)
+#define dec_migrate_count() sub_migrate_count(1)
#ifdef CONFIG_PREEMPT
@@ -51,6 +58,38 @@ do { \
preempt_check_resched(); \
} while (0)
+#define migrate_count() (current_thread_info()->migrate_count)
+#define task_migrate_count(task) (task_thread_info(task)->migrate_count)
+
+#define migrate_disable() \
+do { \
+ inc_migrate_count(); \
+ barrier(); \
+} while (0)
+
+#define migrate_enable_no_check() \
+do { \
+ barrier(); \
+ dec_migrate_count(); \
+} while (0)
+
+#ifdef CONFIG_SMP
+#define check_migrate() \
+do { \
+ if (unlikely(test_thread_flag(TIF_NEED_MIGRATE))) \
+ do_check_migrate(); \
+} while (0)
+#else
+#define check_migrate()
+#endif
+
+#define migrate_enable() \
+do { \
+ migrate_enable_no_check(); \
+ barrier(); \
+ check_migrate(); \
+} while (0)
+
#else
#define preempt_disable() do { } while (0)
@@ -58,6 +97,12 @@ do { \
#define preempt_enable() do { } while (0)
#define preempt_check_resched() do { } while (0)
+#define migrate_count() 0
+#define task_migrate_count(task) 0
+
+#define migrate_disable() do { } while (0)
+#define migrate_enable() do { } while (0)
+
#endif
#endif /* __LINUX_PREEMPT_H */
Index: linux-2.6-lttng/kernel/sched.c
===================================================================
--- linux-2.6-lttng.orig/kernel/sched.c 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/kernel/sched.c 2007-07-14 14:25:33.000000000 -0400
@@ -946,7 +946,7 @@ migrate_task(struct task_struct *p, int
* If the task is not on a runqueue (and not running), then
* it is sufficient to simply update the task's cpu field.
*/
- if (!p->se.on_rq && !task_running(rq, p)) {
+ if (!p->se.on_rq && !task_running(rq, p) && !task_migrate_count(p)) {
set_task_cpu(p, dest_cpu);
return 0;
}
@@ -1347,7 +1347,8 @@ static int try_to_wake_up(struct task_st
#ifdef CONFIG_SMP
if (unlikely(task_running(rq, p)))
goto out_activate;
-
+ if (task_migrate_count(p))
+ goto out_activate;
new_cpu = cpu;
schedstat_inc(rq, ttwu_cnt);
@@ -1534,6 +1535,7 @@ void sched_fork(struct task_struct *p, i
#ifdef CONFIG_PREEMPT
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = 1;
+ task_thread_info(p)->migrate_count = 0;
#endif
put_cpu();
}
@@ -1933,6 +1935,8 @@ static void sched_migrate_task(struct ta
if (!cpu_isset(dest_cpu, p->cpus_allowed)
|| unlikely(cpu_is_offline(dest_cpu)))
goto out;
+ if (task_migrate_count(p))
+ goto out;
trace_mark(kernel_sched_migrate_task, "%d %ld %d",
p->pid, p->state, dest_cpu);
@@ -1996,6 +2000,7 @@ int can_migrate_task(struct task_struct
* 1) running (obviously), or
* 2) cannot be migrated to this CPU due to cpus_allowed, or
* 3) are cache-hot on their current CPU.
+ * 4) migration preemption is non 0 for this non running task.
*/
if (!cpu_isset(this_cpu, p->cpus_allowed))
return 0;
@@ -2003,6 +2008,8 @@ int can_migrate_task(struct task_struct
if (task_running(rq, p))
return 0;
+ if (task_migrate_count(p))
+ return 0;
/*
* Aggressive migration if too many balance attempts have failed:
@@ -3220,6 +3227,29 @@ void fastcall sub_preempt_count(int val)
}
EXPORT_SYMBOL(sub_preempt_count);
+void fastcall add_migrate_count(int val)
+{
+ /*
+ * Underflow?
+ */
+ if (DEBUG_LOCKS_WARN_ON((migrate_count() < 0)))
+ return;
+ migrate_count() += val;
+}
+EXPORT_SYMBOL(add_migrate_count);
+
+void fastcall sub_migrate_count(int val)
+{
+ /*
+ * Underflow?
+ */
+ if (DEBUG_LOCKS_WARN_ON(val > migrate_count()))
+ return;
+
+ migrate_count() -= val;
+}
+EXPORT_SYMBOL(sub_migrate_count);
+
#endif
/*
@@ -3353,6 +3383,28 @@ need_resched_nonpreemptible:
EXPORT_SYMBOL(schedule);
#ifdef CONFIG_PREEMPT
+
+#ifdef CONFIG_SMP
+/*
+ * Wake up the migration thread to deal with our pending migration.
+ * If we have been moved since, we will just wake up the migration thread from
+ * the wrong CPU, which does not hurt anyone. (that's why we use
+ * raw_smp_processor_id()).
+ */
+void __sched do_check_migrate(void)
+{
+ struct rq *rq;
+
+ if (migrate_count())
+ return;
+
+ clear_thread_flag(TIF_NEED_MIGRATE);
+ rq = cpu_rq(raw_smp_processor_id());
+ wake_up_process(rq->migration_thread);
+}
+EXPORT_SYMBOL(do_check_migrate);
+#endif
+
/*
* this is the entry point to schedule() from in-kernel preemption
* off of preempt_enable. Kernel preemptions off return from interrupt
@@ -4814,7 +4866,7 @@ EXPORT_SYMBOL_GPL(set_cpus_allowed);
* So we race with normal scheduler movements, but that's OK, as long
* as the task is no longer on this CPU.
*
- * Returns non-zero if task was successfully migrated.
+ * Returns non-zero if task is not on src_cpu when this function ends.
*/
static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
@@ -4829,13 +4881,17 @@ static int __migrate_task(struct task_st
double_rq_lock(rq_src, rq_dest);
/* Already moved. */
- if (task_cpu(p) != src_cpu)
+ if (task_cpu(p) != src_cpu) {
+ ret = 1;
goto out;
+ }
/* Affinity changed (again). */
if (!cpu_isset(dest_cpu, p->cpus_allowed))
goto out;
on_rq = p->se.on_rq;
+ if (!on_rq && task_migrate_count(p))
+ goto out;
if (on_rq)
deactivate_task(rq_src, p, 0);
set_task_cpu(p, dest_cpu);
@@ -4858,6 +4914,7 @@ static int migration_thread(void *data)
{
int cpu = (long)data;
struct rq *rq;
+ int migrated;
rq = cpu_rq(cpu);
BUG_ON(rq->migration_thread != current);
@@ -4891,10 +4948,42 @@ static int migration_thread(void *data)
list_del_init(head->next);
spin_unlock(&rq->lock);
- __migrate_task(req->task, cpu, req->dest_cpu);
+ migrated = __migrate_task(req->task, cpu, req->dest_cpu);
local_irq_enable();
-
- complete(&req->done);
+ if (!migrated) {
+ /*
+ * If the process has not been migrated, let it run
+ * until it reaches a migration_check() so it can
+ * wake us up.
+ */
+ spin_lock_irq(&rq->lock);
+ head = &rq->migration_queue;
+ list_add(&req->list, head);
+ if (req->task->se.on_rq
+ || !task_migrate_count(req->task)) {
+ /*
+ * The process is on the runqueue, it could
+ * exit its critical section at any moment,
+ * don't race with it and retry actively.
+ * Also, if the thread is not on the runqueue
+ * and has a zero migration count
+ * (__migrate_task failed because cpus allowed
+ * changed), just retry.
+ */
+ spin_unlock_irq(&rq->lock);
+ continue;
+ }
+ set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
+ set_current_state(TASK_INTERRUPTIBLE);
+ spin_unlock_irq(&rq->lock);
+ /*
+ * Wait for the process currently in its critical
+ * section.
+ */
+ wake_up_process(req->task);
+ schedule();
+ } else
+ complete(&req->done);
}
__set_current_state(TASK_RUNNING);
return 0;
Index: linux-2.6-lttng/include/asm-alpha/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-alpha/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-alpha/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -21,6 +21,7 @@ struct thread_info {
mm_segment_t addr_limit; /* thread address space */
unsigned cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
int bpt_nsaved;
unsigned long bpt_addr[2]; /* breakpoint handling */
@@ -77,6 +78,7 @@ register struct thread_info *__current_t
#define TIF_MEMDIE 8
#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal */
#define TIF_SYSCALL_AUDIT 10
+#define TIF_NEED_MIGRATE 11 /* migration necessary */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
@@ -84,6 +86,7 @@ register struct thread_info *__current_t
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
/* Work to do on interrupt/exception return. */
#define _TIF_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED)
Index: linux-2.6-lttng/include/asm-arm/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-arm/thread_info.h 2007-07-14 13:20:10.000000000 -0400
+++ linux-2.6-lttng/include/asm-arm/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -51,6 +51,7 @@ struct cpu_context_save {
struct thread_info {
unsigned long flags; /* low level flags */
int preempt_count; /* 0 => preemptable, <0 => bug */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* address limit */
struct task_struct *task; /* main task structure */
struct exec_domain *exec_domain; /* execution domain */
@@ -72,6 +73,7 @@ struct thread_info {
.exec_domain = &default_exec_domain, \
.flags = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.cpu_domain = domain_val(DOMAIN_USER, DOMAIN_MANAGER) | \
domain_val(DOMAIN_KERNEL, DOMAIN_MANAGER) | \
@@ -137,12 +139,14 @@ extern void iwmmxt_task_switch(struct th
* TIF_SYSCALL_TRACE - syscall trace active
* TIF_SIGPENDING - signal pending
* TIF_NEED_RESCHED - rescheduling necessary
+ * TIF_NEED_MIGRATE - migration necessary
* TIF_USEDFPU - FPU was used by this task this quantum (SMP)
* TIF_POLLING_NRFLAG - true if poll_idle() is polling TIF_NEED_RESCHED
* TIF_SYSCALL_AUDIT - Syscall audting active - LTTng
*/
#define TIF_SIGPENDING 0
#define TIF_NEED_RESCHED 1
+#define TIF_NEED_MIGRATE 2
#define TIF_SYSCALL_AUDIT 7
#define TIF_SYSCALL_TRACE 8
#define TIF_POLLING_NRFLAG 16
@@ -152,6 +156,7 @@ extern void iwmmxt_task_switch(struct th
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-arm26/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-arm26/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-arm26/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -45,6 +45,7 @@ struct cpu_context_save {
struct thread_info {
unsigned long flags; /* low level flags */
int preempt_count; /* 0 => preemptable, <0 => bug */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* address limit */
struct task_struct *task; /* main task structure */
struct exec_domain *exec_domain; /* execution domain */
@@ -60,6 +61,7 @@ struct thread_info {
.exec_domain &default_exec_domain, \
.flags 0, \
.preempt_count 0, \
+ .migrate_count 0, \
.addr_limit KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -112,11 +114,13 @@ extern void free_thread_info(struct thre
* TIF_SYSCALL_TRACE - syscall trace active
* TIF_SIGPENDING - signal pending
* TIF_NEED_RESCHED - rescheduling necessary
+ * TIF_NEED_MIGRATE - migration necessary
* TIF_USEDFPU - FPU was used by this task this quantum (SMP)
* TIF_POLLING_NRFLAG - true if poll_idle() is polling TIF_NEED_RESCHED
*/
#define TIF_SIGPENDING 0
#define TIF_NEED_RESCHED 1
+#define TIF_NEED_MIGRATE 2
#define TIF_SYSCALL_TRACE 8
#define TIF_USED_FPU 16
#define TIF_POLLING_NRFLAG 17
@@ -124,6 +128,7 @@ extern void free_thread_info(struct thre
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_USED_FPU (1 << TIF_USED_FPU)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-avr32/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-avr32/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-avr32/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -25,6 +25,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
__u32 cpu;
__s32 preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
__u8 supervisor_stack[0];
};
@@ -36,6 +37,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall \
} \
@@ -83,6 +85,7 @@ static inline struct thread_info *curren
#define TIF_MEMDIE 6
#define TIF_RESTORE_SIGMASK 7 /* restore signal mask in do_signal */
#define TIF_CPU_GOING_TO_SLEEP 8 /* CPU is entering sleep 0 mode */
+#define TIF_NEED_MIGRATE 9 /* migration necessary */
#define TIF_USERSPACE 31 /* true if FS sets userspace */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
@@ -94,6 +97,7 @@ static inline struct thread_info *curren
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_CPU_GOING_TO_SLEEP (1 << TIF_CPU_GOING_TO_SLEEP)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
/* XXX: These two masks must never span more than 16 bits! */
/* work to do on interrupt/exception return */
Index: linux-2.6-lttng/include/asm-blackfin/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-blackfin/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-blackfin/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -54,6 +54,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* address limit */
struct restart_block restart_block;
struct l1_scratch_task_info l1_task_info;
@@ -69,6 +70,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -125,6 +127,7 @@ static inline struct thread_info *curren
#define TIF_MEMDIE 4
#define TIF_RESTORE_SIGMASK 5 /* restore signal mask in do_signal() */
#define TIF_FREEZE 6 /* is freezing for suspend */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -133,6 +136,7 @@ static inline struct thread_info *curren
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_FREEZE (1<<TIF_FREEZE)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
Index: linux-2.6-lttng/include/asm-cris/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-cris/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-cris/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -32,6 +32,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thead
@@ -58,6 +59,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -81,6 +83,7 @@ struct thread_info {
#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
#define TIF_SIGPENDING 1 /* signal pending */
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
+#define TIF_NEED_MIGRATE 3 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17
@@ -88,6 +91,7 @@ struct thread_info {
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
#define _TIF_ALLWORK_MASK 0x0000FFFF /* work to do on any return to u-space */
Index: linux-2.6-lttng/include/asm-frv/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-frv/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-frv/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -36,6 +36,7 @@ struct thread_info {
unsigned long status; /* thread-synchronous flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thead
@@ -68,6 +69,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -113,6 +115,7 @@ register struct thread_info *__current_t
#define TIF_SINGLESTEP 3 /* restore singlestep on return to user mode */
#define TIF_IRET 4 /* return with iret */
#define TIF_RESTORE_SIGMASK 5 /* restore signal mask in do_signal() */
+#define TIF_NEED_MIGRATE 6 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17 /* OOM killer killed process */
#define TIF_FREEZE 18 /* freezing for suspend */
@@ -125,6 +128,7 @@ register struct thread_info *__current_t
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_FREEZE (1 << TIF_FREEZE)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
#define _TIF_ALLWORK_MASK 0x0000FFFF /* work to do on any return to u-space */
Index: linux-2.6-lttng/include/asm-h8300/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-h8300/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-h8300/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -24,6 +24,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -37,6 +38,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -91,12 +93,14 @@ static inline struct thread_info *curren
#define TIF_POLLING_NRFLAG 3 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 4
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
Index: linux-2.6-lttng/include/asm-ia64/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-ia64/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-ia64/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -30,6 +30,7 @@ struct thread_info {
__u32 status; /* Thread synchronous flags */
mm_segment_t addr_limit; /* user-level address space limit */
int preempt_count; /* 0=premptable, <0=BUG; will also serve as bh-counter */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -43,6 +44,7 @@ struct thread_info {
.cpu = 0, \
.addr_limit = KERNEL_DS, \
.preempt_count = 0, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -86,6 +88,7 @@ struct thread_info {
#define TIF_SINGLESTEP 4 /* restore singlestep on return to user mode */
#define TIF_RESTORE_SIGMASK 5 /* restore signal mask in do_signal() */
#define TIF_PERFMON_WORK 6 /* work for pfm_handle_work() */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17
#define TIF_MCA_INIT 18 /* this task is processing MCA or INIT */
@@ -98,6 +101,7 @@ struct thread_info {
#define _TIF_SYSCALL_TRACEAUDIT (_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_PERFMON_WORK (1 << TIF_PERFMON_WORK)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-m32r/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-m32r/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-m32r/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -29,6 +29,7 @@ struct thread_info {
unsigned long status; /* thread-synchronous flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thread
@@ -69,6 +70,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -150,6 +152,7 @@ static inline unsigned int get_thread_fa
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
#define TIF_SINGLESTEP 3 /* restore singlestep on return to user mode */
#define TIF_IRET 4 /* return with iret */
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
/* 31..28 fault code */
#define TIF_MEMDIE 17
@@ -160,6 +163,7 @@ static inline unsigned int get_thread_fa
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_IRET (1<<TIF_IRET)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
#define _TIF_ALLWORK_MASK 0x0000FFFF /* work to do on any return to u-space */
Index: linux-2.6-lttng/include/asm-m68k/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-m68k/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-m68k/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -9,6 +9,7 @@ struct thread_info {
unsigned long flags;
struct exec_domain *exec_domain; /* execution domain */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
__u32 cpu; /* should always be 0 on m68k */
struct restart_block restart_block;
};
@@ -59,5 +60,6 @@ struct thread_info {
#define TIF_DELAYED_TRACE 14 /* single step a syscall */
#define TIF_SYSCALL_TRACE 15 /* syscall trace active */
#define TIF_MEMDIE 16
+#define TIF_NEED_MIGRATE 17 /* migration necessary */
#endif /* _ASM_M68K_THREAD_INFO_H */
Index: linux-2.6-lttng/include/asm-m68knommu/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-m68knommu/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-m68knommu/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -37,6 +37,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -88,6 +89,7 @@ static inline struct thread_info *curren
#define TIF_POLLING_NRFLAG 3 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 4
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
/* as above, but as bit values */
@@ -96,6 +98,7 @@ static inline struct thread_info *curren
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_MEMDIE (1<<TIF_MEMDIE)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_WORK_MASK 0x0000FFFE /* work to do on interrupt/exception return */
Index: linux-2.6-lttng/include/asm-mips/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-mips/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-mips/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -28,6 +28,7 @@ struct thread_info {
unsigned long tp_value; /* thread pointer */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user-thead
@@ -49,6 +50,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -113,6 +115,7 @@ register struct thread_info *__current_t
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
#define TIF_SYSCALL_AUDIT 3 /* syscall auditing active */
#define TIF_SECCOMP 4 /* secure computing */
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal() */
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling TIF_NEED_RESCHED */
@@ -125,6 +128,7 @@ register struct thread_info *__current_t
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_USEDFPU (1<<TIF_USEDFPU)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-parisc/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-parisc/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-parisc/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -13,6 +13,7 @@ struct thread_info {
mm_segment_t addr_limit; /* user-level address space limit */
__u32 cpu; /* current CPU */
int preempt_count; /* 0=premptable, <0=BUG; will also serve as bh-counter */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -24,6 +25,7 @@ struct thread_info {
.cpu = 0, \
.addr_limit = KERNEL_DS, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall \
} \
@@ -62,6 +64,7 @@ struct thread_info {
#define TIF_32BIT 4 /* 32 bit binary */
#define TIF_MEMDIE 5
#define TIF_RESTORE_SIGMASK 6 /* restore saved signal mask */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
@@ -69,6 +72,7 @@ struct thread_info {
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_32BIT (1 << TIF_32BIT)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | \
_TIF_NEED_RESCHED | _TIF_RESTORE_SIGMASK)
Index: linux-2.6-lttng/include/asm-powerpc/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-powerpc/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-powerpc/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -35,6 +35,7 @@ struct thread_info {
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int migrate_count; /* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
unsigned long local_flags; /* private flags for thread */
@@ -53,6 +54,7 @@ struct thread_info {
.exec_domain = &default_exec_domain, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -124,6 +126,7 @@ static inline struct thread_info *curren
#define TIF_FREEZE 14 /* Freezing for suspend */
#define TIF_RUNLATCH 15 /* Is the runlatch enabled? */
#define TIF_ABI_PENDING 16 /* 32/64 bit switch needed */
+#define TIF_NEED_MIGRATE 17 /* migration necessary */
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -142,6 +145,7 @@ static inline struct thread_info *curren
#define _TIF_FREEZE (1<<TIF_FREEZE)
#define _TIF_RUNLATCH (1<<TIF_RUNLATCH)
#define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_SYSCALL_T_OR_A (_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP)
#define _TIF_USER_WORK_MASK ( _TIF_SIGPENDING | \
Index: linux-2.6-lttng/include/asm-s390/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-s390/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-s390/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -51,6 +51,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
unsigned int cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -64,6 +65,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -96,6 +98,7 @@ static inline struct thread_info *curren
#define TIF_SYSCALL_AUDIT 5 /* syscall auditing active */
#define TIF_SINGLE_STEP 6 /* deliver sigtrap on return to user */
#define TIF_MCCK_PENDING 7 /* machine check handling is pending */
+#define TIF_NEED_MIGRATE 8 /* migration necessary */
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
@@ -110,6 +113,7 @@ static inline struct thread_info *curren
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SINGLE_STEP (1<<TIF_SINGLE_STEP)
#define _TIF_MCCK_PENDING (1<<TIF_MCCK_PENDING)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_USEDFPU (1<<TIF_USEDFPU)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_31BIT (1<<TIF_31BIT)
Index: linux-2.6-lttng/include/asm-sh/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-sh/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-sh/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -21,6 +21,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
__u32 cpu;
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space */
struct restart_block restart_block;
unsigned long previous_sp; /* sp of previous stack in case
@@ -58,6 +59,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -112,6 +114,7 @@ static inline struct thread_info *curren
#define TIF_RESTORE_SIGMASK 3 /* restore signal mask in do_signal() */
#define TIF_SINGLESTEP 4 /* singlestepping active */
#define TIF_SYSCALL_AUDIT 6 /* syscall audit active */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 18
@@ -123,6 +126,7 @@ static inline struct thread_info *curren
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_USEDFPU (1<<TIF_USEDFPU)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_FREEZE (1<<TIF_FREEZE)
Index: linux-2.6-lttng/include/asm-sh64/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-sh64/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-sh64/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -23,6 +23,7 @@ struct thread_info {
unsigned long flags; /* low level flags */
/* Put the 4 32-bit fields together to make asm offsetting easier. */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
__u16 cpu;
mm_segment_t addr_limit;
@@ -41,6 +42,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -80,12 +82,14 @@ static inline struct thread_info *curren
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_MEMDIE 4
#define TIF_RESTORE_SIGMASK 5 /* Restore signal mask in do_signal */
+#define TIF_NEED_MIGRATE 6 /* migration necessary */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#endif /* __KERNEL__ */
Index: linux-2.6-lttng/include/asm-sparc/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-sparc/thread_info.h 2007-07-14 13:20:11.000000000 -0400
+++ linux-2.6-lttng/include/asm-sparc/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -33,6 +33,7 @@ struct thread_info {
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
int softirq_count;
int hardirq_count;
@@ -65,6 +66,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -132,6 +134,7 @@ BTFIXUPDEF_CALL(void, free_thread_info,
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
#define TIF_USEDFPU 8 /* FPU was used by this task
* this quantum (SMP) */
#define TIF_POLLING_NRFLAG 9 /* true if poll_idle() is polling
@@ -144,6 +147,7 @@ BTFIXUPDEF_CALL(void, free_thread_info,
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_USEDFPU (1<<TIF_USEDFPU)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
Index: linux-2.6-lttng/include/asm-sparc64/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-sparc64/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-sparc64/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -47,6 +47,7 @@ struct thread_info {
struct pt_regs *kregs;
struct exec_domain *exec_domain;
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
__u8 new_child;
__u8 syscall_noerror;
__u16 cpu;
@@ -137,6 +138,7 @@ struct thread_info {
.flags = ((unsigned long)ASI_P) << TI_FLAG_CURRENT_DS_SHIFT, \
.exec_domain = &default_exec_domain, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -225,7 +227,7 @@ register struct thread_info *current_thr
#define TIF_UNALIGNED 5 /* allowed to do unaligned accesses */
#define TIF_NEWSIGNALS 6 /* wants new-style signals */
#define TIF_32BIT 7 /* 32-bit binary */
-/* flag bit 8 is available */
+#define TIF_NEED_MIGRATE 8 /* migration necessary */
#define TIF_SECCOMP 9 /* secure computing */
#define TIF_SYSCALL_AUDIT 10 /* syscall auditing active */
/* flag bit 11 is available */
@@ -244,6 +246,7 @@ register struct thread_info *current_thr
#define _TIF_UNALIGNED (1<<TIF_UNALIGNED)
#define _TIF_NEWSIGNALS (1<<TIF_NEWSIGNALS)
#define _TIF_32BIT (1<<TIF_32BIT)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
Index: linux-2.6-lttng/include/asm-um/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-um/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-um/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -18,6 +18,7 @@ struct thread_info {
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space:
0-0xBFFFFFFF for user
0-0xFFFFFFFF for kernel */
@@ -32,6 +33,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -82,6 +84,7 @@ static inline struct thread_info *curren
#define TIF_MEMDIE 5
#define TIF_SYSCALL_AUDIT 6
#define TIF_RESTORE_SIGMASK 7
+#define TIF_NEED_MIGRATE 8 /* migration necessary */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
@@ -90,5 +93,6 @@ static inline struct thread_info *curren
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
+#define _TIF_NEED_MIGRATE (1 << TIF_NEED_MIGRATE)
#endif
Index: linux-2.6-lttng/include/asm-v850/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-v850/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-v850/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -32,6 +32,7 @@ struct thread_info {
int cpu; /* cpu we're on */
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
struct restart_block restart_block;
};
@@ -42,6 +43,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
@@ -82,12 +84,14 @@ struct thread_info {
#define TIF_POLLING_NRFLAG 3 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 4
+#define TIF_NEED_MIGRATE 5 /* migration necessary */
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
/* Size of kernel stack for each process. */
Index: linux-2.6-lttng/include/asm-x86_64/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-x86_64/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-x86_64/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -30,6 +30,7 @@ struct thread_info {
__u32 status; /* thread synchronous flags */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
+ int migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit;
struct restart_block restart_block;
@@ -48,6 +49,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -115,6 +117,7 @@ static inline struct thread_info *stack_
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal */
#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */
+#define TIF_NEED_MIGRATE 11 /* migration necessary */
/* 16 free */
#define TIF_IA32 17 /* 32bit process */
#define TIF_FORK 18 /* ret_from_fork */
@@ -133,6 +136,7 @@ static inline struct thread_info *stack_
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_MCE_NOTIFY (1<<TIF_MCE_NOTIFY)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_IA32 (1<<TIF_IA32)
#define _TIF_FORK (1<<TIF_FORK)
#define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING)
Index: linux-2.6-lttng/include/asm-xtensa/thread_info.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-xtensa/thread_info.h 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/include/asm-xtensa/thread_info.h 2007-07-14 13:20:12.000000000 -0400
@@ -34,6 +34,7 @@ struct thread_info {
unsigned long status; /* thread-synchronous flags */
__u32 cpu; /* current CPU */
__s32 preempt_count; /* 0 => preemptable,< 0 => BUG*/
+ __s32 migrate_count;/* 0: can migrate, <0 => BUG */
mm_segment_t addr_limit; /* thread address space */
struct restart_block restart_block;
@@ -72,6 +73,7 @@ struct thread_info {
.flags = 0, \
.cpu = 0, \
.preempt_count = 1, \
+ .migrate_count = 0, \
.addr_limit = KERNEL_DS, \
.restart_block = { \
.fn = do_no_restart_syscall, \
@@ -116,6 +118,7 @@ static inline struct thread_info *curren
#define TIF_IRET 4 /* return with iret */
#define TIF_MEMDIE 5
#define TIF_RESTORE_SIGMASK 6 /* restore signal mask in do_signal() */
+#define TIF_NEED_MIGRATE 7 /* migration necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -123,6 +126,7 @@ static inline struct thread_info *curren
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_IRET (1<<TIF_IRET)
+#define _TIF_NEED_MIGRATE (1<<TIF_NEED_MIGRATE)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
Index: linux-2.6-lttng/lib/smp_processor_id.c
===================================================================
--- linux-2.6-lttng.orig/lib/smp_processor_id.c 2007-07-13 14:18:26.000000000 -0400
+++ linux-2.6-lttng/lib/smp_processor_id.c 2007-07-14 13:20:12.000000000 -0400
@@ -10,12 +10,16 @@
unsigned int debug_smp_processor_id(void)
{
unsigned long preempt_count = preempt_count();
+ unsigned long migrate_count = migrate_count();
int this_cpu = raw_smp_processor_id();
cpumask_t this_mask;
if (likely(preempt_count))
goto out;
+ if (likely(migrate_count))
+ goto out;
+
if (irqs_disabled())
goto out;
@@ -42,7 +46,7 @@ unsigned int debug_smp_processor_id(void
if (!printk_ratelimit())
goto out_enable;
- printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] code: %s/%d\n", preempt_count(), current->comm, current->pid);
+ printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] migration [%08x] code: %s/%d\n", preempt_count(), migrate_count(), current->comm, current->pid);
print_symbol("caller is %s\n", (long)__builtin_return_address(0));
dump_stack();
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [RFC] Thread Migration Preemption - v4
2007-07-14 18:42 ` [RFC] Thread Migration Preemption - v4 Mathieu Desnoyers
@ 2007-07-14 19:14 ` Peter Zijlstra
2007-07-14 20:25 ` Mathieu Desnoyers
2007-07-14 19:30 ` Peter Zijlstra
2007-07-14 20:23 ` Oleg Nesterov
2 siblings, 1 reply; 16+ messages in thread
From: Peter Zijlstra @ 2007-07-14 19:14 UTC (permalink / raw)
To: Mathieu Desnoyers
Cc: Oleg Nesterov, linux-kernel, Ingo Molnar, Steven Rostedt
Would have been nice if you'd CC'ed me :-/
On Sat, 2007-07-14 at 14:42 -0400, Mathieu Desnoyers wrote:
> @@ -4891,10 +4948,42 @@ static int migration_thread(void *data)
> list_del_init(head->next);
>
> spin_unlock(&rq->lock);
> - __migrate_task(req->task, cpu, req->dest_cpu);
> + migrated = __migrate_task(req->task, cpu, req->dest_cpu);
> local_irq_enable();
> -
> - complete(&req->done);
> + if (!migrated) {
> + /*
> + * If the process has not been migrated, let it run
> + * until it reaches a migration_check() so it can
> + * wake us up.
> + */
> + spin_lock_irq(&rq->lock);
> + head = &rq->migration_queue;
> + list_add(&req->list, head);
> + if (req->task->se.on_rq
> + || !task_migrate_count(req->task)) {
> + /*
> + * The process is on the runqueue, it could
> + * exit its critical section at any moment,
> + * don't race with it and retry actively.
> + * Also, if the thread is not on the runqueue
> + * and has a zero migration count
> + * (__migrate_task failed because cpus allowed
> + * changed), just retry.
> + */
> + spin_unlock_irq(&rq->lock);
> + continue;
> + }
> + set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
> + set_current_state(TASK_INTERRUPTIBLE);
> + spin_unlock_irq(&rq->lock);
> + /*
> + * Wait for the process currently in its critical
> + * section.
> + */
> + wake_up_process(req->task);
> + schedule();
> + } else
> + complete(&req->done);
> }
> __set_current_state(TASK_RUNNING);
> return 0;
I'm not really liking this, this way we hold up all other migration
requests.
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [RFC] Thread Migration Preemption - v4
2007-07-14 19:14 ` Peter Zijlstra
@ 2007-07-14 20:25 ` Mathieu Desnoyers
0 siblings, 0 replies; 16+ messages in thread
From: Mathieu Desnoyers @ 2007-07-14 20:25 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: Oleg Nesterov, linux-kernel, Ingo Molnar, Steven Rostedt
* Peter Zijlstra (a.p.zijlstra@chello.nl) wrote:
> Would have been nice if you'd CC'ed me :-/
>
Sorry
> On Sat, 2007-07-14 at 14:42 -0400, Mathieu Desnoyers wrote:
>
> > @@ -4891,10 +4948,42 @@ static int migration_thread(void *data)
> > list_del_init(head->next);
> >
> > spin_unlock(&rq->lock);
> > - __migrate_task(req->task, cpu, req->dest_cpu);
> > + migrated = __migrate_task(req->task, cpu, req->dest_cpu);
> > local_irq_enable();
> > -
> > - complete(&req->done);
> > + if (!migrated) {
> > + /*
> > + * If the process has not been migrated, let it run
> > + * until it reaches a migration_check() so it can
> > + * wake us up.
> > + */
> > + spin_lock_irq(&rq->lock);
> > + head = &rq->migration_queue;
> > + list_add(&req->list, head);
> > + if (req->task->se.on_rq
> > + || !task_migrate_count(req->task)) {
> > + /*
> > + * The process is on the runqueue, it could
> > + * exit its critical section at any moment,
> > + * don't race with it and retry actively.
> > + * Also, if the thread is not on the runqueue
> > + * and has a zero migration count
> > + * (__migrate_task failed because cpus allowed
> > + * changed), just retry.
> > + */
> > + spin_unlock_irq(&rq->lock);
> > + continue;
> > + }
> > + set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
> > + set_current_state(TASK_INTERRUPTIBLE);
> > + spin_unlock_irq(&rq->lock);
> > + /*
> > + * Wait for the process currently in its critical
> > + * section.
> > + */
> > + wake_up_process(req->task);
> > + schedule();
> > + } else
> > + complete(&req->done);
> > }
> > __set_current_state(TASK_RUNNING);
> > return 0;
>
> I'm not really liking this, this way we hold up all other migration
> requests.
>
True. You approach of delayed migration helps on this.
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [RFC] Thread Migration Preemption - v4
2007-07-14 18:42 ` [RFC] Thread Migration Preemption - v4 Mathieu Desnoyers
2007-07-14 19:14 ` Peter Zijlstra
@ 2007-07-14 19:30 ` Peter Zijlstra
2007-07-14 20:26 ` Mathieu Desnoyers
2007-07-14 20:23 ` Oleg Nesterov
2 siblings, 1 reply; 16+ messages in thread
From: Peter Zijlstra @ 2007-07-14 19:30 UTC (permalink / raw)
To: Mathieu Desnoyers
Cc: Oleg Nesterov, linux-kernel, Ingo Molnar, Steven Rostedt
On Sat, 2007-07-14 at 14:42 -0400, Mathieu Desnoyers wrote:
> Note: (or we could say FIXME)
> Is we ever want to check migration pending in assembly code, we will have to
> make sure we test the right thread flag bits on each architectures. Care should
> also be taken to check that the thread flags used won't trigger false positives
> in non selective asm thread flag checks.
>
> FIXME (HOTPLUG) :
>
> > > /* Affinity changed (again). */
> > > if (!cpu_isset(dest_cpu, p->cpus_allowed))
> > > goto out;
> > >
> > > on_rq = p->se.on_rq;
> > > +#ifdef CONFIG_PREEMPT
> > > + if (!on_rq && task_thread_info(p)->migrate_count)
> > > + goto out;
> > > +#endif
> >
> > This means that move_task_off_dead_cpu() will spin until the task will be
> > scheduled
> > on the dead CPU. Given that we hold tasklist_lock and irqs are disabled, this
> > may
> > never happen.
> >
>
> Yes. My idea to fix this issue is the following:
>
> If a thread has non zero migrate_count, we should still move it to a
> different CPU upon hotplug cpu removal, even if this thread resists
> migration. Care should be taken to send _all_ such threads to the _same_
> CPU so they don't race for the per-cpu ressources. Does it make sense ?
>
> We would have to keep the CPU affinity of the threads running on the
> wrong CPU until they end their migrate disabled section, so that we can
> put them back on their original CPU if it goes back online, otherwise we
> could end up with concurrent per-cpu variables accesses.
>
> (I'll wait for reply before coding a solution for this CPU HOTPLUG
> related problem)
What would, aside from technical issues, be the problem with making
migration_disable() delay CPU_DOWN until migration_enable()?
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [RFC] Thread Migration Preemption - v4
2007-07-14 19:30 ` Peter Zijlstra
@ 2007-07-14 20:26 ` Mathieu Desnoyers
0 siblings, 0 replies; 16+ messages in thread
From: Mathieu Desnoyers @ 2007-07-14 20:26 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: Oleg Nesterov, linux-kernel, Ingo Molnar, Steven Rostedt
* Peter Zijlstra (a.p.zijlstra@chello.nl) wrote:
> On Sat, 2007-07-14 at 14:42 -0400, Mathieu Desnoyers wrote:
>
> > Note: (or we could say FIXME)
> > Is we ever want to check migration pending in assembly code, we will have to
> > make sure we test the right thread flag bits on each architectures. Care should
> > also be taken to check that the thread flags used won't trigger false positives
> > in non selective asm thread flag checks.
> >
> > FIXME (HOTPLUG) :
> >
> > > > /* Affinity changed (again). */
> > > > if (!cpu_isset(dest_cpu, p->cpus_allowed))
> > > > goto out;
> > > >
> > > > on_rq = p->se.on_rq;
> > > > +#ifdef CONFIG_PREEMPT
> > > > + if (!on_rq && task_thread_info(p)->migrate_count)
> > > > + goto out;
> > > > +#endif
> > >
> > > This means that move_task_off_dead_cpu() will spin until the task will be
> > > scheduled
> > > on the dead CPU. Given that we hold tasklist_lock and irqs are disabled, this
> > > may
> > > never happen.
> > >
> >
> > Yes. My idea to fix this issue is the following:
> >
> > If a thread has non zero migrate_count, we should still move it to a
> > different CPU upon hotplug cpu removal, even if this thread resists
> > migration. Care should be taken to send _all_ such threads to the _same_
> > CPU so they don't race for the per-cpu ressources. Does it make sense ?
> >
> > We would have to keep the CPU affinity of the threads running on the
> > wrong CPU until they end their migrate disabled section, so that we can
> > put them back on their original CPU if it goes back online, otherwise we
> > could end up with concurrent per-cpu variables accesses.
> >
> > (I'll wait for reply before coding a solution for this CPU HOTPLUG
> > related problem)
>
> What would, aside from technical issues, be the problem with making
> migration_disable() delay CPU_DOWN until migration_enable()?
>
Because if we thing a little further, migration disabling could be a
very interesting way to provide cheap per-cpu data structure access to
user-space. But we would not want user-space processes to hold CPU_DOWN
forever...
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [RFC] Thread Migration Preemption - v4
2007-07-14 18:42 ` [RFC] Thread Migration Preemption - v4 Mathieu Desnoyers
2007-07-14 19:14 ` Peter Zijlstra
2007-07-14 19:30 ` Peter Zijlstra
@ 2007-07-14 20:23 ` Oleg Nesterov
2007-07-14 20:33 ` Mathieu Desnoyers
2 siblings, 1 reply; 16+ messages in thread
From: Oleg Nesterov @ 2007-07-14 20:23 UTC (permalink / raw)
To: Mathieu Desnoyers; +Cc: linux-kernel, Ingo Molnar, Steven Rostedt
On 07/14, Mathieu Desnoyers wrote:
>
> @@ -4891,10 +4948,42 @@ static int migration_thread(void *data)
> list_del_init(head->next);
>
> spin_unlock(&rq->lock);
> - __migrate_task(req->task, cpu, req->dest_cpu);
> + migrated = __migrate_task(req->task, cpu, req->dest_cpu);
> local_irq_enable();
> -
> - complete(&req->done);
> + if (!migrated) {
> + /*
> + * If the process has not been migrated, let it run
> + * until it reaches a migration_check() so it can
> + * wake us up.
> + */
> + spin_lock_irq(&rq->lock);
> + head = &rq->migration_queue;
> + list_add(&req->list, head);
> + if (req->task->se.on_rq
> + || !task_migrate_count(req->task)) {
> + /*
> + * The process is on the runqueue, it could
> + * exit its critical section at any moment,
> + * don't race with it and retry actively.
> + * Also, if the thread is not on the runqueue
> + * and has a zero migration count
> + * (__migrate_task failed because cpus allowed
> + * changed), just retry.
> + */
> + spin_unlock_irq(&rq->lock);
> + continue;
Again, this can deadlock. migration_thread() is SCHED_FIFO, and it shares the
same CPU with req->task. We are doing a busy-wait loop, req->task may have no
chance to finish its critical section.
> + }
> + set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
> + set_current_state(TASK_INTERRUPTIBLE);
> + spin_unlock_irq(&rq->lock);
> + /*
> + * Wait for the process currently in its critical
> + * section.
> + */
> + wake_up_process(req->task);
> + schedule();
As Peter pointed out, we hold up all other migration requests.
And worse, this can hang forever (until another req comes). do_check_migrate()
can wake_up() the wrong rq.
set_current_state(TASK_INTERRUPTIBLE) is bogus, we can miss a wakeup from
(say) sched_migrate_task().
Oleg.
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [RFC] Thread Migration Preemption - v4
2007-07-14 20:23 ` Oleg Nesterov
@ 2007-07-14 20:33 ` Mathieu Desnoyers
2007-07-14 20:42 ` Oleg Nesterov
0 siblings, 1 reply; 16+ messages in thread
From: Mathieu Desnoyers @ 2007-07-14 20:33 UTC (permalink / raw)
To: Oleg Nesterov; +Cc: linux-kernel, Ingo Molnar, Steven Rostedt
* Oleg Nesterov (oleg@tv-sign.ru) wrote:
> On 07/14, Mathieu Desnoyers wrote:
> >
> > @@ -4891,10 +4948,42 @@ static int migration_thread(void *data)
> > list_del_init(head->next);
> >
> > spin_unlock(&rq->lock);
> > - __migrate_task(req->task, cpu, req->dest_cpu);
> > + migrated = __migrate_task(req->task, cpu, req->dest_cpu);
> > local_irq_enable();
> > -
> > - complete(&req->done);
> > + if (!migrated) {
> > + /*
> > + * If the process has not been migrated, let it run
> > + * until it reaches a migration_check() so it can
> > + * wake us up.
> > + */
> > + spin_lock_irq(&rq->lock);
> > + head = &rq->migration_queue;
> > + list_add(&req->list, head);
> > + if (req->task->se.on_rq
> > + || !task_migrate_count(req->task)) {
> > + /*
> > + * The process is on the runqueue, it could
> > + * exit its critical section at any moment,
> > + * don't race with it and retry actively.
> > + * Also, if the thread is not on the runqueue
> > + * and has a zero migration count
> > + * (__migrate_task failed because cpus allowed
> > + * changed), just retry.
> > + */
> > + spin_unlock_irq(&rq->lock);
> > + continue;
>
> Again, this can deadlock. migration_thread() is SCHED_FIFO, and it shares the
> same CPU with req->task. We are doing a busy-wait loop, req->task may have no
> chance to finish its critical section.
>
If we share the CPU with the other thread, it means that it won't be on
the runqueue while we are holding the rq lock. This first case will then
end up in the else branch.
The other case, !task_migrate_count(req->task), is meant to check if the
process has been scheduled between the unlock/lock of the rq. In this
case, it has already decremented its migrate_count to 0.
> > + }
> > + set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
> > + set_current_state(TASK_INTERRUPTIBLE);
> > + spin_unlock_irq(&rq->lock);
> > + /*
> > + * Wait for the process currently in its critical
> > + * section.
> > + */
> > + wake_up_process(req->task);
> > + schedule();
>
> As Peter pointed out, we hold up all other migration requests.
>
> And worse, this can hang forever (until another req comes). do_check_migrate()
> can wake_up() the wrong rq.
True.
>
> set_current_state(TASK_INTERRUPTIBLE) is bogus, we can miss a wakeup from
> (say) sched_migrate_task().
>
Yep, this is why it's an RFC. We will have to work on this a little
more.
Regards,
Mathieu
> Oleg.
>
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [RFC] Thread Migration Preemption - v4
2007-07-14 20:33 ` Mathieu Desnoyers
@ 2007-07-14 20:42 ` Oleg Nesterov
0 siblings, 0 replies; 16+ messages in thread
From: Oleg Nesterov @ 2007-07-14 20:42 UTC (permalink / raw)
To: Mathieu Desnoyers; +Cc: linux-kernel, Ingo Molnar, Steven Rostedt
On 07/14, Mathieu Desnoyers wrote:
>
> * Oleg Nesterov (oleg@tv-sign.ru) wrote:
> > On 07/14, Mathieu Desnoyers wrote:
> > >
> > > @@ -4891,10 +4948,42 @@ static int migration_thread(void *data)
> > > list_del_init(head->next);
> > >
> > > spin_unlock(&rq->lock);
> > > - __migrate_task(req->task, cpu, req->dest_cpu);
> > > + migrated = __migrate_task(req->task, cpu, req->dest_cpu);
> > > local_irq_enable();
> > > -
> > > - complete(&req->done);
> > > + if (!migrated) {
> > > + /*
> > > + * If the process has not been migrated, let it run
> > > + * until it reaches a migration_check() so it can
> > > + * wake us up.
> > > + */
> > > + spin_lock_irq(&rq->lock);
> > > + head = &rq->migration_queue;
> > > + list_add(&req->list, head);
> > > + if (req->task->se.on_rq
> > > + || !task_migrate_count(req->task)) {
> > > + /*
> > > + * The process is on the runqueue, it could
> > > + * exit its critical section at any moment,
> > > + * don't race with it and retry actively.
> > > + * Also, if the thread is not on the runqueue
> > > + * and has a zero migration count
> > > + * (__migrate_task failed because cpus allowed
> > > + * changed), just retry.
> > > + */
> > > + spin_unlock_irq(&rq->lock);
> > > + continue;
> >
> > Again, this can deadlock. migration_thread() is SCHED_FIFO, and it shares the
> > same CPU with req->task. We are doing a busy-wait loop, req->task may have no
> > chance to finish its critical section.
> >
>
> If we share the CPU with the other thread, it means that it won't be on
> the runqueue while we are holding the rq lock.
Why? The req->task could be runnable, but preempted by migration_thread().
In that case req->task->se.on_rq should be true.
I didn't read the new scheduler yet, but I belive on_rq == 0 only when
the task sleeps, it is like the current ->array = NULL. Please correct
me if I am wrong.
Oleg.
^ permalink raw reply [flat|nested] 16+ messages in thread