* [PATCH tip v5 1/5] wait.[ch]: Introduce the simple waitqueue (swait) implementation
2015-11-30 13:38 [PATCH tip v5 0/5] Simple wait queue support Daniel Wagner
@ 2015-11-30 13:38 ` Daniel Wagner
2015-11-30 13:38 ` [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error Daniel Wagner
` (4 subsequent siblings)
5 siblings, 0 replies; 11+ messages in thread
From: Daniel Wagner @ 2015-11-30 13:38 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Peter Zijlstra (Intel), Daniel Wagner, Paul Gortmaker,
linux-kbuild, Marcelo Tosatti, Paolo Bonzini, Paul E. McKenney,
Thomas Gleixner, Steven Rostedt, Boqun Feng
From: "Peter Zijlstra (Intel)" <peterz@infradead.org>
The existing wait queue support has support for custom wake up call
backs, wake flags, wake key (passed to call back) and exclusive
flags that allow wakers to be tagged as exclusive, for limiting
the number of wakers.
In a lot of cases, none of these features are used, and hence we
can benefit from a slimmed down version that lowers memory overhead
and reduces runtime overhead.
The concept originated from -rt, where waitqueues are a constant
source of trouble, as we can't convert the head lock to a raw
spinlock due to fancy and long lasting callbacks.
With the removal of custom callbacks, we can use a raw lock for
queue list manipulations, hence allowing the simple wait support
to be used in -rt.
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Mostly-Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
[Patch is from PeterZ which is based on Thomas version.
Commit message is written by Paul G.
Daniel:
- And some compile issues fixed.
- Added non-lazy implementation of swake_up_locked as suggested by Boqun Feng.]
---
include/linux/swait.h | 172 ++++++++++++++++++++++++++++++++++++++++++++++++++
kernel/sched/Makefile | 2 +-
kernel/sched/swait.c | 123 ++++++++++++++++++++++++++++++++++++
3 files changed, 296 insertions(+), 1 deletion(-)
create mode 100644 include/linux/swait.h
create mode 100644 kernel/sched/swait.c
diff --git a/include/linux/swait.h b/include/linux/swait.h
new file mode 100644
index 0000000..c1f9c62
--- /dev/null
+++ b/include/linux/swait.h
@@ -0,0 +1,172 @@
+#ifndef _LINUX_SWAIT_H
+#define _LINUX_SWAIT_H
+
+#include <linux/list.h>
+#include <linux/stddef.h>
+#include <linux/spinlock.h>
+#include <asm/current.h>
+
+/*
+ * Simple wait queues
+ *
+ * While these are very similar to the other/complex wait queues (wait.h) the
+ * most important difference is that the simple waitqueue allows for
+ * deterministic behaviour -- IOW it has strictly bounded IRQ and lock hold
+ * times.
+ *
+ * In order to make this so, we had to drop a fair number of features of the
+ * other waitqueue code; notably:
+ *
+ * - mixing INTERRUPTIBLE and UNINTERRUPTIBLE sleeps on the same waitqueue;
+ * all wakeups are TASK_NORMAL in order to avoid O(n) lookups for the right
+ * sleeper state.
+ *
+ * - the exclusive mode; because this requires preserving the list order
+ * and this is hard.
+ *
+ * - custom wake functions; because you cannot give any guarantees about
+ * random code.
+ *
+ * As a side effect of this; the data structures are slimmer.
+ *
+ * One would recommend using this wait queue where possible.
+ */
+
+struct task_struct;
+
+struct swait_queue_head {
+ raw_spinlock_t lock;
+ struct list_head task_list;
+};
+
+struct swait_queue {
+ struct task_struct *task;
+ struct list_head task_list;
+};
+
+#define __SWAITQUEUE_INITIALIZER(name) { \
+ .task = current, \
+ .task_list = LIST_HEAD_INIT((name).task_list), \
+}
+
+#define DECLARE_SWAITQUEUE(name) \
+ struct swait_queue name = __SWAITQUEUE_INITIALIZER(name)
+
+#define __SWAIT_QUEUE_HEAD_INITIALIZER(name) { \
+ .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \
+ .task_list = LIST_HEAD_INIT((name).task_list), \
+}
+
+#define DECLARE_SWAIT_QUEUE_HEAD(name) \
+ struct swait_queue_head name = __SWAIT_QUEUE_HEAD_INITIALIZER(name)
+
+extern void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
+ struct lock_class_key *key);
+
+#define init_swait_queue_head(q) \
+ do { \
+ static struct lock_class_key __key; \
+ __init_swait_queue_head((q), #q, &__key); \
+ } while (0)
+
+#ifdef CONFIG_LOCKDEP
+# define __SWAIT_QUEUE_HEAD_INIT_ONSTACK(name) \
+ ({ init_swait_queue_head(&name); name; })
+# define DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(name) \
+ struct swait_queue_head name = __SWAIT_QUEUE_HEAD_INIT_ONSTACK(name)
+#else
+# define DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(name) \
+ DECLARE_SWAIT_QUEUE_HEAD(name)
+#endif
+
+static inline int swait_active(struct swait_queue_head *q)
+{
+ return !list_empty(&q->task_list);
+}
+
+extern void swake_up(struct swait_queue_head *q);
+extern void swake_up_all(struct swait_queue_head *q);
+extern void swake_up_locked(struct swait_queue_head *q);
+
+extern void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
+extern void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state);
+extern long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state);
+
+extern void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait);
+extern void finish_swait(struct swait_queue_head *q, struct swait_queue *wait);
+
+/* as per ___wait_event() but for swait, therefore "exclusive == 0" */
+#define ___swait_event(wq, condition, state, ret, cmd) \
+({ \
+ struct swait_queue __wait; \
+ long __ret = ret; \
+ \
+ INIT_LIST_HEAD(&__wait.task_list); \
+ for (;;) { \
+ long __int = prepare_to_swait_event(&wq, &__wait, state);\
+ \
+ if (condition) \
+ break; \
+ \
+ if (___wait_is_interruptible(state) && __int) { \
+ __ret = __int; \
+ break; \
+ } \
+ \
+ cmd; \
+ } \
+ finish_swait(&wq, &__wait); \
+ __ret; \
+})
+
+#define __swait_event(wq, condition) \
+ (void)___swait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, \
+ schedule())
+
+#define swait_event(wq, condition) \
+do { \
+ if (condition) \
+ break; \
+ __swait_event(wq, condition); \
+} while (0)
+
+#define __swait_event_timeout(wq, condition, timeout) \
+ ___swait_event(wq, ___wait_cond_timeout(condition), \
+ TASK_UNINTERRUPTIBLE, timeout, \
+ __ret = schedule_timeout(__ret))
+
+#define swait_event_timeout(wq, condition, timeout) \
+({ \
+ long __ret = timeout; \
+ if (!___wait_cond_timeout(condition)) \
+ __ret = __swait_event_timeout(wq, condition, timeout); \
+ __ret; \
+})
+
+#define __swait_event_interruptible(wq, condition) \
+ ___swait_event(wq, condition, TASK_INTERRUPTIBLE, 0, \
+ schedule())
+
+#define swait_event_interruptible(wq, condition) \
+({ \
+ int __ret = 0; \
+ if (!(condition)) \
+ __ret = __swait_event_interruptible(wq, condition); \
+ __ret; \
+})
+
+#define __swait_event_interruptible_timeout(wq, condition, timeout) \
+ ___swait_event(wq, ___wait_cond_timeout(condition), \
+ TASK_INTERRUPTIBLE, timeout, \
+ __ret = schedule_timeout(__ret))
+
+#define swait_event_interruptible_timeout(wq, condition, timeout) \
+({ \
+ long __ret = timeout; \
+ if (!___wait_cond_timeout(condition)) \
+ __ret = __swait_event_interruptible_timeout(wq, \
+ condition, timeout); \
+ __ret; \
+})
+
+#endif /* _LINUX_SWAIT_H */
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 6768797..7d4cba2 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -13,7 +13,7 @@ endif
obj-y += core.o loadavg.o clock.o cputime.o
obj-y += idle_task.o fair.o rt.o deadline.o stop_task.o
-obj-y += wait.o completion.o idle.o
+obj-y += wait.o swait.o completion.o idle.o
obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o
obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o
obj-$(CONFIG_SCHEDSTATS) += stats.o
diff --git a/kernel/sched/swait.c b/kernel/sched/swait.c
new file mode 100644
index 0000000..82f0dff
--- /dev/null
+++ b/kernel/sched/swait.c
@@ -0,0 +1,123 @@
+#include <linux/sched.h>
+#include <linux/swait.h>
+
+void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
+ struct lock_class_key *key)
+{
+ raw_spin_lock_init(&q->lock);
+ lockdep_set_class_and_name(&q->lock, key, name);
+ INIT_LIST_HEAD(&q->task_list);
+}
+EXPORT_SYMBOL(__init_swait_queue_head);
+
+/*
+ * The thing about the wake_up_state() return value; I think we can ignore it.
+ *
+ * If for some reason it would return 0, that means the previously waiting
+ * task is already running, so it will observe condition true (or has already).
+ */
+void swake_up_locked(struct swait_queue_head *q)
+{
+ struct swait_queue *curr;
+
+ if (list_empty(&q->task_list))
+ return;
+
+ curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
+ wake_up_process(curr->task);
+ list_del_init(&curr->task_list);
+}
+EXPORT_SYMBOL(swake_up_locked);
+
+void swake_up(struct swait_queue_head *q)
+{
+ unsigned long flags;
+
+ if (!swait_active(q))
+ return;
+
+ raw_spin_lock_irqsave(&q->lock, flags);
+ swake_up_locked(q);
+ raw_spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(swake_up);
+
+/*
+ * Does not allow usage from IRQ disabled, since we must be able to
+ * release IRQs to guarantee bounded hold time.
+ */
+void swake_up_all(struct swait_queue_head *q)
+{
+ struct swait_queue *curr;
+ LIST_HEAD(tmp);
+
+ if (!swait_active(q))
+ return;
+
+ raw_spin_lock_irq(&q->lock);
+ list_splice_init(&q->task_list, &tmp);
+ while (!list_empty(&tmp)) {
+ curr = list_first_entry(&tmp, typeof(*curr), task_list);
+
+ wake_up_state(curr->task, TASK_NORMAL);
+ list_del_init(&curr->task_list);
+
+ if (list_empty(&tmp))
+ break;
+
+ raw_spin_unlock_irq(&q->lock);
+ raw_spin_lock_irq(&q->lock);
+ }
+ raw_spin_unlock_irq(&q->lock);
+}
+EXPORT_SYMBOL(swake_up_all);
+
+void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
+{
+ wait->task = current;
+ if (list_empty(&wait->task_list))
+ list_add(&wait->task_list, &q->task_list);
+}
+
+void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&q->lock, flags);
+ __prepare_to_swait(q, wait);
+ set_current_state(state);
+ raw_spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(prepare_to_swait);
+
+long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
+{
+ if (signal_pending_state(state, current))
+ return -ERESTARTSYS;
+
+ prepare_to_swait(q, wait, state);
+
+ return 0;
+}
+EXPORT_SYMBOL(prepare_to_swait_event);
+
+void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
+{
+ __set_current_state(TASK_RUNNING);
+ if (!list_empty(&wait->task_list))
+ list_del_init(&wait->task_list);
+}
+
+void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
+{
+ unsigned long flags;
+
+ __set_current_state(TASK_RUNNING);
+
+ if (!list_empty_careful(&wait->task_list)) {
+ raw_spin_lock_irqsave(&q->lock, flags);
+ list_del_init(&wait->task_list);
+ raw_spin_unlock_irqrestore(&q->lock, flags);
+ }
+}
+EXPORT_SYMBOL(finish_swait);
--
2.4.3
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error
2015-11-30 13:38 [PATCH tip v5 0/5] Simple wait queue support Daniel Wagner
2015-11-30 13:38 ` [PATCH tip v5 1/5] wait.[ch]: Introduce the simple waitqueue (swait) implementation Daniel Wagner
@ 2015-11-30 13:38 ` Daniel Wagner
2015-11-30 15:26 ` Daniel Wagner
2016-01-27 12:03 ` Thomas Gleixner
2015-11-30 13:38 ` [PATCH tip v5 3/5] KVM: use simple waitqueue for vcpu->wq Daniel Wagner
` (3 subsequent siblings)
5 siblings, 2 replies; 11+ messages in thread
From: Daniel Wagner @ 2015-11-30 13:38 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Daniel Wagner, Thomas Gleixner, Peter Zijlstra, linux-kbuild,
Marcelo Tosatti, Paolo Bonzini, Paul E. McKenney, Paul Gortmaker,
Steven Rostedt, Boqun Feng
With the introduction of the simple wait API we have two very
similar APIs in the kernel. For example wake_up() and swake_up()
is only one character away. Although the compiler will warn
happily the wrong usage it keeps on going an even links the kernel.
Thomas and Peter would rather like to see early missuses reported
as error early on.
In a first attempt we tried to wrap all swait and wait calls
into a macro which has an compile time type assertion. The result
was pretty ugly and wasn't able to catch all wrong usages.
woken_wake_function(), autoremove_wake_function() and wake_bit_function()
are assigned as function pointers. Wrapping them with a macro around is
not possible. Prefixing them with '_' was also not a real option
because there some users in the kernel which do use them as well.
All in all this attempt looked to intrusive and too ugly.
An alternative is to turn the pointer type check into an error which
catches wrong type uses. Obviously not only the swait/wait ones. That
isn't a bad thing either. Though for the beginning let's introduce it
as options in the kernel hacking section.
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
---
Makefile | 4 ++++
lib/Kconfig.debug | 7 +++++++
2 files changed, 11 insertions(+)
diff --git a/Makefile b/Makefile
index 416660d..8817273 100644
--- a/Makefile
+++ b/Makefile
@@ -625,6 +625,10 @@ KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks,) \
$(call cc-option,-fno-partial-inlining)
endif
+ifdef CONFIG_ENABLE_ERR_TYPE_CHECK
+KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
+endif
+
ifneq ($(CONFIG_FRAME_WARN),0)
KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ab76b99..21c0193 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -194,6 +194,13 @@ config ENABLE_MUST_CHECK
suppress the "warning: ignoring return value of 'foo', declared with
attribute warn_unused_result" messages.
+config ENABLE_ERR_TYPE_CHECK
+ bool "Turn pointer type check into an error"
+ default n
+ help
+ Instead of just warning that a wrong pointer type is used,
+ bail with a proper compile error.
+
config FRAME_WARN
int "Warn for stack frames larger than (needs gcc 4.4)"
range 0 8192
--
2.4.3
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error
2015-11-30 13:38 ` [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error Daniel Wagner
@ 2015-11-30 15:26 ` Daniel Wagner
2015-11-30 17:38 ` Paul E. McKenney
2016-01-27 12:03 ` Thomas Gleixner
1 sibling, 1 reply; 11+ messages in thread
From: Daniel Wagner @ 2015-11-30 15:26 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Peter Zijlstra, linux-kbuild, Marcelo Tosatti,
Paolo Bonzini, Paul E. McKenney, Paul Gortmaker, Steven Rostedt,
Boqun Feng
On 11/30/2015 02:38 PM, Daniel Wagner wrote:
> With the introduction of the simple wait API we have two very
> similar APIs in the kernel. For example wake_up() and swake_up()
> is only one character away. Although the compiler will warn
> happily the wrong usage it keeps on going an even links the kernel.
> Thomas and Peter would rather like to see early missuses reported
> as error early on.
>
> In a first attempt we tried to wrap all swait and wait calls
> into a macro which has an compile time type assertion. The result
> was pretty ugly and wasn't able to catch all wrong usages.
> woken_wake_function(), autoremove_wake_function() and wake_bit_function()
> are assigned as function pointers. Wrapping them with a macro around is
> not possible. Prefixing them with '_' was also not a real option
> because there some users in the kernel which do use them as well.
> All in all this attempt looked to intrusive and too ugly.
>
> An alternative is to turn the pointer type check into an error which
> catches wrong type uses. Obviously not only the swait/wait ones. That
> isn't a bad thing either. Though for the beginning let's introduce it
> as options in the kernel hacking section.
The kbuild bot found one problem for allmodconfig. I just send a fix for
it ("regmap: Fix leftover from struct reg_default to struct reg_sequence
change").
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error
2015-11-30 15:26 ` Daniel Wagner
@ 2015-11-30 17:38 ` Paul E. McKenney
2015-11-30 18:52 ` Daniel Wagner
0 siblings, 1 reply; 11+ messages in thread
From: Paul E. McKenney @ 2015-11-30 17:38 UTC (permalink / raw)
To: Daniel Wagner
Cc: linux-kernel, linux-rt-users, Thomas Gleixner, Peter Zijlstra,
linux-kbuild, Marcelo Tosatti, Paolo Bonzini, Paul Gortmaker,
Steven Rostedt, Boqun Feng
On Mon, Nov 30, 2015 at 04:26:03PM +0100, Daniel Wagner wrote:
> On 11/30/2015 02:38 PM, Daniel Wagner wrote:
> > With the introduction of the simple wait API we have two very
> > similar APIs in the kernel. For example wake_up() and swake_up()
> > is only one character away. Although the compiler will warn
> > happily the wrong usage it keeps on going an even links the kernel.
> > Thomas and Peter would rather like to see early missuses reported
> > as error early on.
> >
> > In a first attempt we tried to wrap all swait and wait calls
> > into a macro which has an compile time type assertion. The result
> > was pretty ugly and wasn't able to catch all wrong usages.
> > woken_wake_function(), autoremove_wake_function() and wake_bit_function()
> > are assigned as function pointers. Wrapping them with a macro around is
> > not possible. Prefixing them with '_' was also not a real option
> > because there some users in the kernel which do use them as well.
> > All in all this attempt looked to intrusive and too ugly.
> >
> > An alternative is to turn the pointer type check into an error which
> > catches wrong type uses. Obviously not only the swait/wait ones. That
> > isn't a bad thing either. Though for the beginning let's introduce it
> > as options in the kernel hacking section.
>
> The kbuild bot found one problem for allmodconfig. I just send a fix for
> it ("regmap: Fix leftover from struct reg_default to struct reg_sequence
> change").
This will result in an updated series, correct?
Thanx, Paul
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error
2015-11-30 17:38 ` Paul E. McKenney
@ 2015-11-30 18:52 ` Daniel Wagner
0 siblings, 0 replies; 11+ messages in thread
From: Daniel Wagner @ 2015-11-30 18:52 UTC (permalink / raw)
To: paulmck, Daniel Wagner
Cc: linux-kernel, linux-rt-users, Thomas Gleixner, Peter Zijlstra,
linux-kbuild, Marcelo Tosatti, Paolo Bonzini, Paul Gortmaker,
Steven Rostedt, Boqun Feng
Hi Paul,
On 11/30/2015 06:38 PM, Paul E. McKenney wrote:
> On Mon, Nov 30, 2015 at 04:26:03PM +0100, Daniel Wagner wrote:
>> On 11/30/2015 02:38 PM, Daniel Wagner wrote:
>>> With the introduction of the simple wait API we have two very
>>> similar APIs in the kernel. For example wake_up() and swake_up()
>>> is only one character away. Although the compiler will warn
>>> happily the wrong usage it keeps on going an even links the kernel.
>>> Thomas and Peter would rather like to see early missuses reported
>>> as error early on.
>>>
>>> In a first attempt we tried to wrap all swait and wait calls
>>> into a macro which has an compile time type assertion. The result
>>> was pretty ugly and wasn't able to catch all wrong usages.
>>> woken_wake_function(), autoremove_wake_function() and wake_bit_function()
>>> are assigned as function pointers. Wrapping them with a macro around is
>>> not possible. Prefixing them with '_' was also not a real option
>>> because there some users in the kernel which do use them as well.
>>> All in all this attempt looked to intrusive and too ugly.
>>>
>>> An alternative is to turn the pointer type check into an error which
>>> catches wrong type uses. Obviously not only the swait/wait ones. That
>>> isn't a bad thing either. Though for the beginning let's introduce it
>>> as options in the kernel hacking section.
>>
>> The kbuild bot found one problem for allmodconfig. I just send a fix for
>> it ("regmap: Fix leftover from struct reg_default to struct reg_sequence
>> change").
>
> This will result in an updated series, correct?
Not necessarily. This patch just points very verbose the incorrect
pointer usage in regmap_register_path() users with allmodconfig. This
series itself should be okay (unless I missed something).
cheers,
daniel
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error
2015-11-30 13:38 ` [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error Daniel Wagner
2015-11-30 15:26 ` Daniel Wagner
@ 2016-01-27 12:03 ` Thomas Gleixner
1 sibling, 0 replies; 11+ messages in thread
From: Thomas Gleixner @ 2016-01-27 12:03 UTC (permalink / raw)
To: Daniel Wagner
Cc: linux-kernel, linux-rt-users, Peter Zijlstra, linux-kbuild,
Marcelo Tosatti, Paolo Bonzini, Paul E. McKenney, Paul Gortmaker,
Steven Rostedt, Boqun Feng
On Mon, 30 Nov 2015, Daniel Wagner wrote:
>
> +ifdef CONFIG_ENABLE_ERR_TYPE_CHECK
> +KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
> +endif
I don't see a value for making this configurable. If the compiler supports it,
we should use it. It already found a bug, so why would we make that optional?
Thanks,
tglx
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH tip v5 3/5] KVM: use simple waitqueue for vcpu->wq
2015-11-30 13:38 [PATCH tip v5 0/5] Simple wait queue support Daniel Wagner
2015-11-30 13:38 ` [PATCH tip v5 1/5] wait.[ch]: Introduce the simple waitqueue (swait) implementation Daniel Wagner
2015-11-30 13:38 ` [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error Daniel Wagner
@ 2015-11-30 13:38 ` Daniel Wagner
2015-11-30 13:38 ` [PATCH tip v5 4/5] rcu: Do not call rcu_nocb_gp_cleanup() while holding rnp->lock Daniel Wagner
` (2 subsequent siblings)
5 siblings, 0 replies; 11+ messages in thread
From: Daniel Wagner @ 2015-11-30 13:38 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Marcelo Tosatti, Daniel Wagner, Paolo Bonzini, linux-kbuild,
Paul E. McKenney, Paul Gortmaker, Peter Zijlstra (Intel),
Thomas Gleixner, Steven Rostedt, Boqun Feng
From: Marcelo Tosatti <mtosatti@redhat.com>
The problem:
On -rt, an emulated LAPIC timer instances has the following path:
1) hard interrupt
2) ksoftirqd is scheduled
3) ksoftirqd wakes up vcpu thread
4) vcpu thread is scheduled
This extra context switch introduces unnecessary latency in the
LAPIC path for a KVM guest.
The solution:
Allow waking up vcpu thread from hardirq context,
thus avoiding the need for ksoftirqd to be scheduled.
Normal waitqueues make use of spinlocks, which on -RT
are sleepable locks. Therefore, waking up a waitqueue
waiter involves locking a sleeping lock, which
is not allowed from hard interrupt context.
cyclictest command line:
This patch reduces the average latency in my tests from 14us to 11us.
Daniel writes:
Paolo asked for numbers from kvm-unit-tests/tscdeadline_latency
benchmark on mainline. The test was run 382, respectively 300 times:
./x86-run x86/tscdeadline_latency.flat -cpu host
with idle=poll.
The test seems not to deliver really stable numbers though most of
them are smaller. Paolo write:
"Anything above ~10000 cycles means that the host went to C1 or
lower---the number means more or less nothing in that case.
The mean shows an improvement indeed."
Before:
min max mean std
count 382.000000 382.000000 382.000000 382.000000
mean 6068.552356 269502.528796 8056.016198 3912.128273
std 707.404966 848866.474783 1062.472704 9835.891707
min 2335.000000 29828.000000 7337.426000 445.738750
25% 6004.500000 44237.500000 7471.094250 1078.834837
50% 6372.000000 64175.000000 7663.133700 1783.172446
75% 6465.500000 150384.500000 8210.771900 2759.734524
max 6886.000000 10188451.000000 15466.434000 120469.205668
After
min max mean std
count 300.000000 300.000000 300.000000 300.000000
mean 5618.380000 217464.786667 7745.545114 3258.483272
std 824.719741 516371.888369 847.391685 5632.943904
min 3494.000000 31410.000000 7083.574800 438.445477
25% 4937.000000 45446.000000 7214.102850 1045.536261
50% 6118.000000 67023.000000 7417.330800 1699.574075
75% 6224.000000 134191.500000 7871.625600 2809.536185
max 6654.000000 4570896.000000 13528.788600 52206.226799
[Patch was originaly based on the swait implementation found in the -rt
tree. Daniel ported it to mainline's version and gathered the
benchmark numbers for tscdeadline_latency test.]
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
---
arch/arm/kvm/arm.c | 4 ++--
arch/arm/kvm/psci.c | 4 ++--
arch/mips/kvm/mips.c | 8 ++++----
arch/powerpc/include/asm/kvm_host.h | 4 ++--
arch/powerpc/kvm/book3s_hv.c | 23 +++++++++++------------
arch/s390/include/asm/kvm_host.h | 2 +-
arch/s390/kvm/interrupt.c | 8 ++++----
arch/x86/kvm/lapic.c | 6 +++---
include/linux/kvm_host.h | 5 +++--
virt/kvm/async_pf.c | 4 ++--
virt/kvm/kvm_main.c | 17 ++++++++---------
11 files changed, 42 insertions(+), 43 deletions(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index dc017ad..97e8336 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -470,9 +470,9 @@ bool kvm_arch_intc_initialized(struct kvm *kvm)
static void vcpu_pause(struct kvm_vcpu *vcpu)
{
- wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
+ struct swait_queue_head *wq = kvm_arch_vcpu_wq(vcpu);
- wait_event_interruptible(*wq, !vcpu->arch.pause);
+ swait_event_interruptible(*wq, !vcpu->arch.pause);
}
static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
index ad6f642..2b93577 100644
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -70,7 +70,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
{
struct kvm *kvm = source_vcpu->kvm;
struct kvm_vcpu *vcpu = NULL;
- wait_queue_head_t *wq;
+ struct swait_queue_head *wq;
unsigned long cpu_id;
unsigned long context_id;
phys_addr_t target_pc;
@@ -119,7 +119,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
smp_mb(); /* Make sure the above is visible */
wq = kvm_arch_vcpu_wq(vcpu);
- wake_up_interruptible(wq);
+ swake_up(wq);
return PSCI_RET_SUCCESS;
}
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 49ff3bf..290161d 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -442,8 +442,8 @@ int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu,
dvcpu->arch.wait = 0;
- if (waitqueue_active(&dvcpu->wq))
- wake_up_interruptible(&dvcpu->wq);
+ if (swait_active(&dvcpu->wq))
+ swake_up(&dvcpu->wq);
return 0;
}
@@ -1171,8 +1171,8 @@ static void kvm_mips_comparecount_func(unsigned long data)
kvm_mips_callbacks->queue_timer_int(vcpu);
vcpu->arch.wait = 0;
- if (waitqueue_active(&vcpu->wq))
- wake_up_interruptible(&vcpu->wq);
+ if (swait_active(&vcpu->wq))
+ swake_up(&vcpu->wq);
}
/* low level hrtimer wake routine */
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 827a38d..12e9835 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -286,7 +286,7 @@ struct kvmppc_vcore {
struct list_head runnable_threads;
struct list_head preempt_list;
spinlock_t lock;
- wait_queue_head_t wq;
+ struct swait_queue_head wq;
spinlock_t stoltb_lock; /* protects stolen_tb and preempt_tb */
u64 stolen_tb;
u64 preempt_tb;
@@ -628,7 +628,7 @@ struct kvm_vcpu_arch {
u8 prodded;
u32 last_inst;
- wait_queue_head_t *wqp;
+ struct swait_queue_head *wqp;
struct kvmppc_vcore *vcore;
int ret;
int trap;
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 2280497..f534e15 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -121,11 +121,11 @@ static bool kvmppc_ipi_thread(int cpu)
static void kvmppc_fast_vcpu_kick_hv(struct kvm_vcpu *vcpu)
{
int cpu;
- wait_queue_head_t *wqp;
+ struct swait_queue_head *wqp;
wqp = kvm_arch_vcpu_wq(vcpu);
- if (waitqueue_active(wqp)) {
- wake_up_interruptible(wqp);
+ if (swait_active(wqp)) {
+ swake_up(wqp);
++vcpu->stat.halt_wakeup;
}
@@ -708,8 +708,8 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
tvcpu->arch.prodded = 1;
smp_mb();
if (vcpu->arch.ceded) {
- if (waitqueue_active(&vcpu->wq)) {
- wake_up_interruptible(&vcpu->wq);
+ if (swait_active(&vcpu->wq)) {
+ swake_up(&vcpu->wq);
vcpu->stat.halt_wakeup++;
}
}
@@ -1448,7 +1448,7 @@ static struct kvmppc_vcore *kvmppc_vcore_create(struct kvm *kvm, int core)
INIT_LIST_HEAD(&vcore->runnable_threads);
spin_lock_init(&vcore->lock);
spin_lock_init(&vcore->stoltb_lock);
- init_waitqueue_head(&vcore->wq);
+ init_swait_queue_head(&vcore->wq);
vcore->preempt_tb = TB_NIL;
vcore->lpcr = kvm->arch.lpcr;
vcore->first_vcpuid = core * threads_per_subcore;
@@ -2560,10 +2560,9 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc)
{
struct kvm_vcpu *vcpu;
int do_sleep = 1;
+ DECLARE_SWAITQUEUE(wait);
- DEFINE_WAIT(wait);
-
- prepare_to_wait(&vc->wq, &wait, TASK_INTERRUPTIBLE);
+ prepare_to_swait(&vc->wq, &wait, TASK_INTERRUPTIBLE);
/*
* Check one last time for pending exceptions and ceded state after
@@ -2577,7 +2576,7 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc)
}
if (!do_sleep) {
- finish_wait(&vc->wq, &wait);
+ finish_swait(&vc->wq, &wait);
return;
}
@@ -2585,7 +2584,7 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc)
trace_kvmppc_vcore_blocked(vc, 0);
spin_unlock(&vc->lock);
schedule();
- finish_wait(&vc->wq, &wait);
+ finish_swait(&vc->wq, &wait);
spin_lock(&vc->lock);
vc->vcore_state = VCORE_INACTIVE;
trace_kvmppc_vcore_blocked(vc, 1);
@@ -2641,7 +2640,7 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
kvmppc_start_thread(vcpu, vc);
trace_kvm_guest_enter(vcpu);
} else if (vc->vcore_state == VCORE_SLEEPING) {
- wake_up(&vc->wq);
+ swake_up(&vc->wq);
}
}
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 8ced426..a044ddb 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -427,7 +427,7 @@ struct kvm_s390_irq_payload {
struct kvm_s390_local_interrupt {
spinlock_t lock;
struct kvm_s390_float_interrupt *float_int;
- wait_queue_head_t *wq;
+ struct swait_queue_head *wq;
atomic_t *cpuflags;
DECLARE_BITMAP(sigp_emerg_pending, KVM_MAX_VCPUS);
struct kvm_s390_irq_payload irq;
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 5c2c169..78625fa 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -884,13 +884,13 @@ no_timer:
void kvm_s390_vcpu_wakeup(struct kvm_vcpu *vcpu)
{
- if (waitqueue_active(&vcpu->wq)) {
+ if (swait_active(&vcpu->wq)) {
/*
* The vcpu gave up the cpu voluntarily, mark it as a good
* yield-candidate.
*/
vcpu->preempted = true;
- wake_up_interruptible(&vcpu->wq);
+ swake_up(&vcpu->wq);
vcpu->stat.halt_wakeup++;
}
}
@@ -994,7 +994,7 @@ int kvm_s390_inject_program_int(struct kvm_vcpu *vcpu, u16 code)
spin_lock(&li->lock);
irq.u.pgm.code = code;
__inject_prog(vcpu, &irq);
- BUG_ON(waitqueue_active(li->wq));
+ BUG_ON(swait_active(li->wq));
spin_unlock(&li->lock);
return 0;
}
@@ -1009,7 +1009,7 @@ int kvm_s390_inject_prog_irq(struct kvm_vcpu *vcpu,
spin_lock(&li->lock);
irq.u.pgm = *pgm_info;
rc = __inject_prog(vcpu, &irq);
- BUG_ON(waitqueue_active(li->wq));
+ BUG_ON(swait_active(li->wq));
spin_unlock(&li->lock);
return rc;
}
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 8d9013c..a59aead 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1117,7 +1117,7 @@ static void apic_update_lvtt(struct kvm_lapic *apic)
static void apic_timer_expired(struct kvm_lapic *apic)
{
struct kvm_vcpu *vcpu = apic->vcpu;
- wait_queue_head_t *q = &vcpu->wq;
+ struct swait_queue_head *q = &vcpu->wq;
struct kvm_timer *ktimer = &apic->lapic_timer;
if (atomic_read(&apic->lapic_timer.pending))
@@ -1126,8 +1126,8 @@ static void apic_timer_expired(struct kvm_lapic *apic)
atomic_inc(&apic->lapic_timer.pending);
kvm_set_pending_timer(vcpu);
- if (waitqueue_active(q))
- wake_up_interruptible(q);
+ if (swait_active(q))
+ swake_up(q);
if (apic_lvtt_tscdeadline(apic))
ktimer->expired_tscdeadline = ktimer->tscdeadline;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1bef9e2..7b6231e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -24,6 +24,7 @@
#include <linux/err.h>
#include <linux/irqflags.h>
#include <linux/context_tracking.h>
+#include <linux/swait.h>
#include <asm/signal.h>
#include <linux/kvm.h>
@@ -237,7 +238,7 @@ struct kvm_vcpu {
int fpu_active;
int guest_fpu_loaded, guest_xcr0_loaded;
unsigned char fpu_counter;
- wait_queue_head_t wq;
+ struct swait_queue_head wq;
struct pid *pid;
int sigset_active;
sigset_t sigset;
@@ -759,7 +760,7 @@ static inline bool kvm_arch_has_assigned_device(struct kvm *kvm)
}
#endif
-static inline wait_queue_head_t *kvm_arch_vcpu_wq(struct kvm_vcpu *vcpu)
+static inline struct swait_queue_head *kvm_arch_vcpu_wq(struct kvm_vcpu *vcpu)
{
#ifdef __KVM_HAVE_ARCH_WQP
return vcpu->arch.wqp;
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 44660ae..ff4891c 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -94,8 +94,8 @@ static void async_pf_execute(struct work_struct *work)
trace_kvm_async_pf_completed(addr, gva);
- if (waitqueue_active(&vcpu->wq))
- wake_up_interruptible(&vcpu->wq);
+ if (swait_active(&vcpu->wq))
+ swake_up(&vcpu->wq);
mmput(mm);
kvm_put_kvm(vcpu->kvm);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8db1d93..45ab55f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -226,8 +226,7 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
vcpu->kvm = kvm;
vcpu->vcpu_id = id;
vcpu->pid = NULL;
- vcpu->halt_poll_ns = 0;
- init_waitqueue_head(&vcpu->wq);
+ init_swait_queue_head(&vcpu->wq);
kvm_async_pf_vcpu_init(vcpu);
page = alloc_page(GFP_KERNEL | __GFP_ZERO);
@@ -1996,7 +1995,7 @@ static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
void kvm_vcpu_block(struct kvm_vcpu *vcpu)
{
ktime_t start, cur;
- DEFINE_WAIT(wait);
+ DECLARE_SWAITQUEUE(wait);
bool waited = false;
u64 block_ns;
@@ -2019,7 +2018,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
}
for (;;) {
- prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
+ prepare_to_swait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
if (kvm_vcpu_check_block(vcpu) < 0)
break;
@@ -2028,7 +2027,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
schedule();
}
- finish_wait(&vcpu->wq, &wait);
+ finish_swait(&vcpu->wq, &wait);
cur = ktime_get();
out:
@@ -2059,11 +2058,11 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
{
int me;
int cpu = vcpu->cpu;
- wait_queue_head_t *wqp;
+ struct swait_queue_head *wqp;
wqp = kvm_arch_vcpu_wq(vcpu);
- if (waitqueue_active(wqp)) {
- wake_up_interruptible(wqp);
+ if (swait_active(wqp)) {
+ swake_up(wqp);
++vcpu->stat.halt_wakeup;
}
@@ -2164,7 +2163,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
continue;
if (vcpu == me)
continue;
- if (waitqueue_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
+ if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
continue;
if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
continue;
--
2.4.3
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH tip v5 4/5] rcu: Do not call rcu_nocb_gp_cleanup() while holding rnp->lock
2015-11-30 13:38 [PATCH tip v5 0/5] Simple wait queue support Daniel Wagner
` (2 preceding siblings ...)
2015-11-30 13:38 ` [PATCH tip v5 3/5] KVM: use simple waitqueue for vcpu->wq Daniel Wagner
@ 2015-11-30 13:38 ` Daniel Wagner
2015-11-30 13:38 ` [PATCH tip v5 5/5] rcu: use simple wait queues where possible in rcutree Daniel Wagner
2016-01-27 12:08 ` [PATCH tip v5 0/5] Simple wait queue support Peter Zijlstra
5 siblings, 0 replies; 11+ messages in thread
From: Daniel Wagner @ 2015-11-30 13:38 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Daniel Wagner, Paul E. McKenney, Peter Zijlstra, Thomas Gleixner,
linux-kbuild, Marcelo Tosatti, Paolo Bonzini, Paul Gortmaker,
Steven Rostedt, Boqun Feng
rcu_nocb_gp_cleanup() is called while holding rnp->lock. Currently,
this is okay because the wake_up_all() in rcu_nocb_gp_cleanup() will
not enable the IRQs. lockdep is happy.
By switching over using swait this is not true anymore. swake_up_all()
enables the IRQs while processing the waiters. __do_softirq() can now
run and will eventually call rcu_process_callbacks() which wants to
grap nrp->lock.
Let's move the rcu_nocb_gp_cleanup() call outside the lock before we
switch over to swait.
If we would hold the rnp->lock and use swait, lockdep reports
following:
=================================
[ INFO: inconsistent lock state ]
4.2.0-rc5-00025-g9a73ba0 #136 Not tainted
---------------------------------
inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
rcu_preempt/8 [HC0[0]:SC0[0]:HE1:SE1] takes:
(rcu_node_1){+.?...}, at: [<ffffffff811387c7>] rcu_gp_kthread+0xb97/0xeb0
{IN-SOFTIRQ-W} state was registered at:
[<ffffffff81109b9f>] __lock_acquire+0xd5f/0x21e0
[<ffffffff8110be0f>] lock_acquire+0xdf/0x2b0
[<ffffffff81841cc9>] _raw_spin_lock_irqsave+0x59/0xa0
[<ffffffff81136991>] rcu_process_callbacks+0x141/0x3c0
[<ffffffff810b1a9d>] __do_softirq+0x14d/0x670
[<ffffffff810b2214>] irq_exit+0x104/0x110
[<ffffffff81844e96>] smp_apic_timer_interrupt+0x46/0x60
[<ffffffff81842e70>] apic_timer_interrupt+0x70/0x80
[<ffffffff810dba66>] rq_attach_root+0xa6/0x100
[<ffffffff810dbc2d>] cpu_attach_domain+0x16d/0x650
[<ffffffff810e4b42>] build_sched_domains+0x942/0xb00
[<ffffffff821777c2>] sched_init_smp+0x509/0x5c1
[<ffffffff821551e3>] kernel_init_freeable+0x172/0x28f
[<ffffffff8182cdce>] kernel_init+0xe/0xe0
[<ffffffff8184231f>] ret_from_fork+0x3f/0x70
irq event stamp: 76
hardirqs last enabled at (75): [<ffffffff81841330>] _raw_spin_unlock_irq+0x30/0x60
hardirqs last disabled at (76): [<ffffffff8184116f>] _raw_spin_lock_irq+0x1f/0x90
softirqs last enabled at (0): [<ffffffff810a8df2>] copy_process.part.26+0x602/0x1cf0
softirqs last disabled at (0): [< (null)>] (null)
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(rcu_node_1);
<Interrupt>
lock(rcu_node_1);
*** DEADLOCK ***
1 lock held by rcu_preempt/8:
#0: (rcu_node_1){+.?...}, at: [<ffffffff811387c7>] rcu_gp_kthread+0xb97/0xeb0
stack backtrace:
CPU: 0 PID: 8 Comm: rcu_preempt Not tainted 4.2.0-rc5-00025-g9a73ba0 #136
Hardware name: Dell Inc. PowerEdge R820/066N7P, BIOS 2.0.20 01/16/2014
0000000000000000 000000006d7e67d8 ffff881fb081fbd8 ffffffff818379e0
0000000000000000 ffff881fb0812a00 ffff881fb081fc38 ffffffff8110813b
0000000000000000 0000000000000001 ffff881f00000001 ffffffff8102fa4f
Call Trace:
[<ffffffff818379e0>] dump_stack+0x4f/0x7b
[<ffffffff8110813b>] print_usage_bug+0x1db/0x1e0
[<ffffffff8102fa4f>] ? save_stack_trace+0x2f/0x50
[<ffffffff811087ad>] mark_lock+0x66d/0x6e0
[<ffffffff81107790>] ? check_usage_forwards+0x150/0x150
[<ffffffff81108898>] mark_held_locks+0x78/0xa0
[<ffffffff81841330>] ? _raw_spin_unlock_irq+0x30/0x60
[<ffffffff81108a28>] trace_hardirqs_on_caller+0x168/0x220
[<ffffffff81108aed>] trace_hardirqs_on+0xd/0x10
[<ffffffff81841330>] _raw_spin_unlock_irq+0x30/0x60
[<ffffffff810fd1c7>] swake_up_all+0xb7/0xe0
[<ffffffff811386e1>] rcu_gp_kthread+0xab1/0xeb0
[<ffffffff811089bf>] ? trace_hardirqs_on_caller+0xff/0x220
[<ffffffff81841341>] ? _raw_spin_unlock_irq+0x41/0x60
[<ffffffff81137c30>] ? rcu_barrier+0x20/0x20
[<ffffffff810d2014>] kthread+0x104/0x120
[<ffffffff81841330>] ? _raw_spin_unlock_irq+0x30/0x60
[<ffffffff810d1f10>] ? kthread_create_on_node+0x260/0x260
[<ffffffff8184231f>] ret_from_fork+0x3f/0x70
[<ffffffff810d1f10>] ? kthread_create_on_node+0x260/0x260
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
kernel/rcu/tree.c | 4 +++-
kernel/rcu/tree.h | 3 ++-
kernel/rcu/tree_plugin.h | 16 +++++++++++++---
3 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 775d36c..ff02ffb 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1568,7 +1568,6 @@ static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
int needmore;
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
- rcu_nocb_gp_cleanup(rsp, rnp);
rnp->need_future_gp[c & 0x1] = 0;
needmore = rnp->need_future_gp[(c + 1) & 0x1];
trace_rcu_future_gp(rnp, rdp, c,
@@ -1972,6 +1971,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
int nocb = 0;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
+ wait_queue_head_t *sq;
WRITE_ONCE(rsp->gp_activity, jiffies);
raw_spin_lock_irq(&rnp->lock);
@@ -2010,7 +2010,9 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
needgp = __note_gp_changes(rsp, rnp, rdp) || needgp;
/* smp_mb() provided by prior unlock-lock pair. */
nocb += rcu_future_gp_cleanup(rsp, rnp);
+ sq = rcu_nocb_gp_get(rnp);
raw_spin_unlock_irq(&rnp->lock);
+ rcu_nocb_gp_cleanup(sq);
cond_resched_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
rcu_gp_slow(rsp, gp_cleanup_delay);
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 2e991f8..00a12b7 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -608,7 +608,8 @@ static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static void increment_cpu_stall_ticks(void);
static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
-static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp);
+static wait_queue_head_t *rcu_nocb_gp_get(struct rcu_node *rnp);
+static void rcu_nocb_gp_cleanup(wait_queue_head_t *sq);
static void rcu_init_one_nocb(struct rcu_node *rnp);
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
bool lazy, unsigned long flags);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index b2bf396..07019b4 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1777,9 +1777,9 @@ early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
* Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
* grace period.
*/
-static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
+static void rcu_nocb_gp_cleanup(wait_queue_head_t *sq)
{
- wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]);
+ wake_up_all(sq);
}
/*
@@ -1795,6 +1795,11 @@ static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq;
}
+static wait_queue_head_t *rcu_nocb_gp_get(struct rcu_node *rnp)
+{
+ return &rnp->nocb_gp_wq[rnp->completed & 0x1];
+}
+
static void rcu_init_one_nocb(struct rcu_node *rnp)
{
init_waitqueue_head(&rnp->nocb_gp_wq[0]);
@@ -2469,7 +2474,7 @@ static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
return false;
}
-static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
+static void rcu_nocb_gp_cleanup(wait_queue_head_t *sq)
{
}
@@ -2477,6 +2482,11 @@ static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
{
}
+static wait_queue_head_t *rcu_nocb_gp_get(struct rcu_node *rnp)
+{
+ return NULL;
+}
+
static void rcu_init_one_nocb(struct rcu_node *rnp)
{
}
--
2.4.3
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH tip v5 5/5] rcu: use simple wait queues where possible in rcutree
2015-11-30 13:38 [PATCH tip v5 0/5] Simple wait queue support Daniel Wagner
` (3 preceding siblings ...)
2015-11-30 13:38 ` [PATCH tip v5 4/5] rcu: Do not call rcu_nocb_gp_cleanup() while holding rnp->lock Daniel Wagner
@ 2015-11-30 13:38 ` Daniel Wagner
2016-01-27 12:08 ` [PATCH tip v5 0/5] Simple wait queue support Peter Zijlstra
5 siblings, 0 replies; 11+ messages in thread
From: Daniel Wagner @ 2015-11-30 13:38 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Paul Gortmaker, Daniel Wagner, Paul E. McKenney,
Peter Zijlstra (Intel), Thomas Gleixner, linux-kbuild,
Marcelo Tosatti, Paolo Bonzini, Steven Rostedt, Boqun Feng
From: Paul Gortmaker <paul.gortmaker@windriver.com>
As of commit dae6e64d2bcfd4b06304ab864c7e3a4f6b5fedf4 ("rcu: Introduce
proper blocking to no-CBs kthreads GP waits") the RCU subsystem started
making use of wait queues.
Here we convert all additions of RCU wait queues to use simple wait queues,
since they don't need the extra overhead of the full wait queue features.
Originally this was done for RT kernels[1], since we would get things like...
BUG: sleeping function called from invalid context at kernel/rtmutex.c:659
in_atomic(): 1, irqs_disabled(): 1, pid: 8, name: rcu_preempt
Pid: 8, comm: rcu_preempt Not tainted
Call Trace:
[<ffffffff8106c8d0>] __might_sleep+0xd0/0xf0
[<ffffffff817d77b4>] rt_spin_lock+0x24/0x50
[<ffffffff8106fcf6>] __wake_up+0x36/0x70
[<ffffffff810c4542>] rcu_gp_kthread+0x4d2/0x680
[<ffffffff8105f910>] ? __init_waitqueue_head+0x50/0x50
[<ffffffff810c4070>] ? rcu_gp_fqs+0x80/0x80
[<ffffffff8105eabb>] kthread+0xdb/0xe0
[<ffffffff8106b912>] ? finish_task_switch+0x52/0x100
[<ffffffff817e0754>] kernel_thread_helper+0x4/0x10
[<ffffffff8105e9e0>] ? __init_kthread_worker+0x60/0x60
[<ffffffff817e0750>] ? gs_change+0xb/0xb
...and hence simple wait queues were deployed on RT out of necessity
(as simple wait uses a raw lock), but mainline might as well take
advantage of the more streamline support as well.
[1] This is a carry forward of work from v3.10-rt; the original conversion
was by Thomas on an earlier -rt version, and Sebastian extended it to
additional post-3.10 added RCU waiters; here I've added a commit log and
unified the RCU changes into one, and uprev'd it to match mainline RCU.
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
kernel/rcu/tree.c | 22 +++++++++++-----------
kernel/rcu/tree.h | 13 +++++++------
kernel/rcu/tree_plugin.h | 26 +++++++++++++-------------
3 files changed, 31 insertions(+), 30 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index ff02ffb..628ffb5 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1588,7 +1588,7 @@ static void rcu_gp_kthread_wake(struct rcu_state *rsp)
!READ_ONCE(rsp->gp_flags) ||
!rsp->gp_kthread)
return;
- wake_up(&rsp->gp_wq);
+ swake_up(&rsp->gp_wq);
}
/*
@@ -1971,7 +1971,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
int nocb = 0;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
- wait_queue_head_t *sq;
+ struct swait_queue_head *sq;
WRITE_ONCE(rsp->gp_activity, jiffies);
raw_spin_lock_irq(&rnp->lock);
@@ -2059,7 +2059,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
READ_ONCE(rsp->gpnum),
TPS("reqwait"));
rsp->gp_state = RCU_GP_WAIT_GPS;
- wait_event_interruptible(rsp->gp_wq,
+ swait_event_interruptible(rsp->gp_wq,
READ_ONCE(rsp->gp_flags) &
RCU_GP_FLAG_INIT);
rsp->gp_state = RCU_GP_DONE_GPS;
@@ -2089,7 +2089,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
READ_ONCE(rsp->gpnum),
TPS("fqswait"));
rsp->gp_state = RCU_GP_WAIT_FQS;
- ret = wait_event_interruptible_timeout(rsp->gp_wq,
+ ret = swait_event_interruptible_timeout(rsp->gp_wq,
rcu_gp_fqs_check_wake(rsp, &gf), j);
rsp->gp_state = RCU_GP_DOING_FQS;
/* Locking provides needed memory barriers. */
@@ -2212,7 +2212,7 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS);
raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
- rcu_gp_kthread_wake(rsp);
+ swake_up(&rsp->gp_wq); /* Memory barrier implied by swake_up() path. */
}
/*
@@ -2873,7 +2873,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
}
WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS);
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
- rcu_gp_kthread_wake(rsp);
+ swake_up(&rsp->gp_wq); /* Memory barrier implied by swake_up() path. */
}
/*
@@ -3465,7 +3465,7 @@ static int synchronize_sched_expedited_cpu_stop(void *data)
/* We are here: If we are last, do the wakeup. */
rdp->exp_done = true;
if (atomic_dec_and_test(&rsp->expedited_need_qs))
- wake_up(&rsp->expedited_wq);
+ swake_up(&rsp->expedited_wq);
return 0;
}
@@ -3481,7 +3481,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
jiffies_start = jiffies;
for (;;) {
- ret = wait_event_interruptible_timeout(
+ ret = swait_event_timeout(
rsp->expedited_wq,
!atomic_read(&rsp->expedited_need_qs),
jiffies_stall);
@@ -3489,7 +3489,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
return;
if (ret < 0) {
/* Hit a signal, disable CPU stall warnings. */
- wait_event(rsp->expedited_wq,
+ swait_event(rsp->expedited_wq,
!atomic_read(&rsp->expedited_need_qs));
return;
}
@@ -3558,7 +3558,7 @@ void synchronize_sched_expedited(void)
rcu_exp_gp_seq_start(rsp);
/* Stop each CPU that is online, non-idle, and not us. */
- init_waitqueue_head(&rsp->expedited_wq);
+ init_swait_queue_head(&rsp->expedited_wq);
atomic_set(&rsp->expedited_need_qs, 1); /* Extra count avoids race. */
for_each_online_cpu(cpu) {
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
@@ -4180,7 +4180,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
}
}
- init_waitqueue_head(&rsp->gp_wq);
+ init_swait_queue_head(&rsp->gp_wq);
rnp = rsp->level[rcu_num_lvls - 1];
for_each_possible_cpu(i) {
while (i > rnp->grphi)
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 00a12b7..02c29d3 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -27,6 +27,7 @@
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
+#include <linux/swait.h>
#include <linux/stop_machine.h>
/*
@@ -244,7 +245,7 @@ struct rcu_node {
/* Refused to boost: not sure why, though. */
/* This can happen due to race conditions. */
#ifdef CONFIG_RCU_NOCB_CPU
- wait_queue_head_t nocb_gp_wq[2];
+ struct swait_queue_head nocb_gp_wq[2];
/* Place for rcu_nocb_kthread() to wait GP. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
int need_future_gp[2];
@@ -388,7 +389,7 @@ struct rcu_data {
atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */
struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
struct rcu_head **nocb_follower_tail;
- wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */
+ struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */
struct task_struct *nocb_kthread;
int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
@@ -475,7 +476,7 @@ struct rcu_state {
unsigned long gpnum; /* Current gp number. */
unsigned long completed; /* # of last completed gp. */
struct task_struct *gp_kthread; /* Task for grace periods. */
- wait_queue_head_t gp_wq; /* Where GP task waits. */
+ struct swait_queue_head gp_wq; /* Where GP task waits. */
short gp_flags; /* Commands for GP task. */
short gp_state; /* GP kthread sleep state. */
@@ -507,7 +508,7 @@ struct rcu_state {
atomic_long_t expedited_workdone3; /* # done by others #3. */
atomic_long_t expedited_normal; /* # fallbacks to normal. */
atomic_t expedited_need_qs; /* # CPUs left to check in. */
- wait_queue_head_t expedited_wq; /* Wait for check-ins. */
+ struct swait_queue_head expedited_wq; /* Wait for check-ins. */
unsigned long jiffies_force_qs; /* Time at which to invoke */
/* force_quiescent_state(). */
@@ -608,8 +609,8 @@ static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static void increment_cpu_stall_ticks(void);
static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
-static wait_queue_head_t *rcu_nocb_gp_get(struct rcu_node *rnp);
-static void rcu_nocb_gp_cleanup(wait_queue_head_t *sq);
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
static void rcu_init_one_nocb(struct rcu_node *rnp);
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
bool lazy, unsigned long flags);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 07019b4..0c69868 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1777,9 +1777,9 @@ early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
* Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
* grace period.
*/
-static void rcu_nocb_gp_cleanup(wait_queue_head_t *sq)
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
{
- wake_up_all(sq);
+ swake_up_all(sq);
}
/*
@@ -1795,15 +1795,15 @@ static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq;
}
-static wait_queue_head_t *rcu_nocb_gp_get(struct rcu_node *rnp)
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
{
return &rnp->nocb_gp_wq[rnp->completed & 0x1];
}
static void rcu_init_one_nocb(struct rcu_node *rnp)
{
- init_waitqueue_head(&rnp->nocb_gp_wq[0]);
- init_waitqueue_head(&rnp->nocb_gp_wq[1]);
+ init_swait_queue_head(&rnp->nocb_gp_wq[0]);
+ init_swait_queue_head(&rnp->nocb_gp_wq[1]);
}
#ifndef CONFIG_RCU_NOCB_CPU_ALL
@@ -1828,7 +1828,7 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force)
if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) {
/* Prior smp_mb__after_atomic() orders against prior enqueue. */
WRITE_ONCE(rdp_leader->nocb_leader_sleep, false);
- wake_up(&rdp_leader->nocb_wq);
+ swake_up(&rdp_leader->nocb_wq);
}
}
@@ -2041,7 +2041,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
*/
trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait"));
for (;;) {
- wait_event_interruptible(
+ swait_event_interruptible(
rnp->nocb_gp_wq[c & 0x1],
(d = ULONG_CMP_GE(READ_ONCE(rnp->completed), c)));
if (likely(d))
@@ -2069,7 +2069,7 @@ wait_again:
/* Wait for callbacks to appear. */
if (!rcu_nocb_poll) {
trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep");
- wait_event_interruptible(my_rdp->nocb_wq,
+ swait_event_interruptible(my_rdp->nocb_wq,
!READ_ONCE(my_rdp->nocb_leader_sleep));
/* Memory barrier handled by smp_mb() calls below and repoll. */
} else if (firsttime) {
@@ -2144,7 +2144,7 @@ wait_again:
* List was empty, wake up the follower.
* Memory barriers supplied by atomic_long_add().
*/
- wake_up(&rdp->nocb_wq);
+ swake_up(&rdp->nocb_wq);
}
}
@@ -2165,7 +2165,7 @@ static void nocb_follower_wait(struct rcu_data *rdp)
if (!rcu_nocb_poll) {
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
"FollowerSleep");
- wait_event_interruptible(rdp->nocb_wq,
+ swait_event_interruptible(rdp->nocb_wq,
READ_ONCE(rdp->nocb_follower_head));
} else if (firsttime) {
/* Don't drown trace log with "Poll"! */
@@ -2324,7 +2324,7 @@ void __init rcu_init_nohz(void)
static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
{
rdp->nocb_tail = &rdp->nocb_head;
- init_waitqueue_head(&rdp->nocb_wq);
+ init_swait_queue_head(&rdp->nocb_wq);
rdp->nocb_follower_tail = &rdp->nocb_follower_head;
}
@@ -2474,7 +2474,7 @@ static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
return false;
}
-static void rcu_nocb_gp_cleanup(wait_queue_head_t *sq)
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
{
}
@@ -2482,7 +2482,7 @@ static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
{
}
-static wait_queue_head_t *rcu_nocb_gp_get(struct rcu_node *rnp)
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
{
return NULL;
}
--
2.4.3
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH tip v5 0/5] Simple wait queue support
2015-11-30 13:38 [PATCH tip v5 0/5] Simple wait queue support Daniel Wagner
` (4 preceding siblings ...)
2015-11-30 13:38 ` [PATCH tip v5 5/5] rcu: use simple wait queues where possible in rcutree Daniel Wagner
@ 2016-01-27 12:08 ` Peter Zijlstra
5 siblings, 0 replies; 11+ messages in thread
From: Peter Zijlstra @ 2016-01-27 12:08 UTC (permalink / raw)
To: Daniel Wagner
Cc: linux-kernel, linux-rt-users, linux-kbuild, Marcelo Tosatti,
Paolo Bonzini, Paul E. McKenney, Paul Gortmaker, Thomas Gleixner,
Steven Rostedt, Boqun Feng
Thanks!
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
^ permalink raw reply [flat|nested] 11+ messages in thread