[GIT PULL] scheduler fixes

Ingo Molnar
2012-02-02T10:07:30Z

Linus,

Please pull the latest sched-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-for-linus

HEAD: cb297a3e433dbdcf7ad81e0564e7b804c941ff0d sched/rt: Fix task stack corruption under __ARCH_WANT_INTERRUPTS_ON_CTXSW

Thanks,

Ingo

------------------>
Chanho Min (1):
sched/rt: Fix task stack corruption under __ARCH_WANT_INTERRUPTS_ON_CTXSW

Christian Borntraeger (1):
sched/s390: Fix compile error in sched/core.c

Peter Zijlstra (1):
sched: Fix rq->nr_uninterruptible update race

Suresh Siddha (1):
sched/nohz: Fix nohz cpu idle load balancing state with cpu hotplug

Yasunori Goto (1):
sched: Fix ancient race in do_exit()

kernel/exit.c | 16 ++++++++++++++++
kernel/sched/core.c | 19 +++++++------------
kernel/sched/fair.c | 34 +++++++++++++++++++++++++++++-----
kernel/sched/rt.c | 5 +++++
4 files changed, 57 insertions(+), 17 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 294b170..4b4042f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1038,6 +1038,22 @@ void do_exit(long code)
if (tsk->nr_dirtied)
__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
exit_rcu();
+
+ /*
+ * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
+ * when the following two conditions become true.
+ * - There is race condition of mmap_sem (It is acquired by
+ * exit_mm()), and
+ * - SMI occurs before setting TASK_RUNINNG.
+ * (or hypervisor of virtual machine switches to other guest)
+ * As a result, we may become TASK_RUNNING after becoming TASK_DEAD
+ *
+ * To avoid it, we have to wait for releasing tsk->pi_lock which
+ * is held by try_to_wake_up()
+ */
+ smp_mb();
+ raw_spin_unlock_wait(&tsk->pi_lock);
+
/* causes final put_task_struct in finish_task_switch(). */
tsk->state = TASK_DEAD;
tsk->flags |= PF_NOFREEZE; /* tell freezer to ignore us */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index df00cb0..5255c9d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -74,6 +74,7 @@

#include <asm/tlb.h>
#include <asm/irq_regs.h>
+#include <asm/mutex.h>
#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
#endif
@@ -723,9 +724,6 @@ static void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
p->sched_class->dequeue_task(rq, p, flags);
}

-/*
- * activate_task - move a task to the runqueue.
- */
void activate_task(struct rq *rq, struct task_struct *p, int flags)
{
if (task_contributes_to_load(p))
@@ -734,9 +732,6 @@ void activate_task(struct rq *rq, struct task_struct *p, int flags)
enqueue_task(rq, p, flags);
}

-/*
- * deactivate_task - remove a task from the runqueue.
- */
void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
{
if (task_contributes_to_load(p))
@@ -4134,7 +4129,7 @@ recheck:
on_rq = p->on_rq;
running = task_current(rq, p);
if (on_rq)
- deactivate_task(rq, p, 0);
+ dequeue_task(rq, p, 0);
if (running)
p->sched_class->put_prev_task(rq, p);

@@ -4147,7 +4142,7 @@ recheck:
if (running)
p->sched_class->set_curr_task(rq);
if (on_rq)
- activate_task(rq, p, 0);
+ enqueue_task(rq, p, 0);

check_class_changed(rq, p, prev_class, oldprio);
task_rq_unlock(rq, p, &flags);
@@ -4998,9 +4993,9 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
* placed properly.
*/
if (p->on_rq) {
- deactivate_task(rq_src, p, 0);
+ dequeue_task(rq_src, p, 0);
set_task_cpu(p, dest_cpu);
- activate_task(rq_dest, p, 0);
+ enqueue_task(rq_dest, p, 0);
check_preempt_curr(rq_dest, p, 0);
}
done:
@@ -7032,10 +7027,10 @@ static void normalize_task(struct rq *rq, struct task_struct *p)

on_rq = p->on_rq;
if (on_rq)
- deactivate_task(rq, p, 0);
+ dequeue_task(rq, p, 0);
__setscheduler(rq, p, SCHED_NORMAL, 0);
if (on_rq) {
- activate_task(rq, p, 0);
+ enqueue_task(rq, p, 0);
resched_task(rq->curr);
}

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 84adb2d..7c6414f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4866,6 +4866,15 @@ static void nohz_balancer_kick(int cpu)
return;
}

+static inline void clear_nohz_tick_stopped(int cpu)
+{
+ if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
+ cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
+ atomic_dec(&nohz.nr_cpus);
+ clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
+ }
+}
+
static inline void set_cpu_sd_state_busy(void)
{
struct sched_domain *sd;
@@ -4904,6 +4913,12 @@ void select_nohz_load_balancer(int stop_tick)
{
int cpu = smp_processor_id();

+ /*
+ * If this cpu is going down, then nothing needs to be done.
+ */
+ if (!cpu_active(cpu))
+ return;
+
if (stop_tick) {
if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
return;
@@ -4914,6 +4929,18 @@ void select_nohz_load_balancer(int stop_tick)
}
return;
}
+
+static int __cpuinit sched_ilb_notifier(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ switch (action & ~CPU_TASKS_FROZEN) {
+ case CPU_DYING:
+ clear_nohz_tick_stopped(smp_processor_id());
+ return NOTIFY_OK;
+ default:
+ return NOTIFY_DONE;
+ }
+}
#endif

static DEFINE_SPINLOCK(balancing);
@@ -5070,11 +5097,7 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu)
* busy tick after returning from idle, we will update the busy stats.
*/
set_cpu_sd_state_busy();
- if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
- clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
- cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
- atomic_dec(&nohz.nr_cpus);
- }
+ clear_nohz_tick_stopped(cpu);

/*
* None are in tickless mode and hence no need for NOHZ idle load
@@ -5590,6 +5613,7 @@ __init void init_sched_fair_class(void)

#ifdef CONFIG_NO_HZ
zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
+ cpu_notifier(sched_ilb_notifier, 0);
#endif
#endif /* SMP */

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3640ebb..f42ae7f 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1587,6 +1587,11 @@ static int push_rt_task(struct rq *rq)
if (!next_task)
return 0;

+#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
+ if (unlikely(task_running(rq, next_task)))
+ return 0;
+#endif
+
retry:
if (unlikely(next_task == rq->curr)) {
WARN_ON(1);