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authorLinus Torvalds <torvalds@linux-foundation.org>2013-06-20 08:18:35 -1000
committerLinus Torvalds <torvalds@linux-foundation.org>2013-06-20 08:18:35 -1000
commita3d5c3460a86f52ea435b3fb98be112bd18faabc (patch)
tree48a32968b569af0e0f0af1def3effa0770710fea /kernel
parent86c76676cfdbf283f6131d5a2783bed3f3d490ea (diff)
parent29bb9e5a75684106a37593ad75ec75ff8312731b (diff)
downloadop-kernel-dev-a3d5c3460a86f52ea435b3fb98be112bd18faabc.zip
op-kernel-dev-a3d5c3460a86f52ea435b3fb98be112bd18faabc.tar.gz
Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar: "Two smaller fixes - plus a context tracking tracing fix that is a bit bigger" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: tracing/context-tracking: Add preempt_schedule_context() for tracing sched: Fix clear NOHZ_BALANCE_KICK sched/x86: Construct all sibling maps if smt
Diffstat (limited to 'kernel')
-rw-r--r--kernel/context_tracking.c40
-rw-r--r--kernel/sched/core.c21
2 files changed, 57 insertions, 4 deletions
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 85bdde1..383f823 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -70,6 +70,46 @@ void user_enter(void)
local_irq_restore(flags);
}
+#ifdef CONFIG_PREEMPT
+/**
+ * preempt_schedule_context - preempt_schedule called by tracing
+ *
+ * The tracing infrastructure uses preempt_enable_notrace to prevent
+ * recursion and tracing preempt enabling caused by the tracing
+ * infrastructure itself. But as tracing can happen in areas coming
+ * from userspace or just about to enter userspace, a preempt enable
+ * can occur before user_exit() is called. This will cause the scheduler
+ * to be called when the system is still in usermode.
+ *
+ * To prevent this, the preempt_enable_notrace will use this function
+ * instead of preempt_schedule() to exit user context if needed before
+ * calling the scheduler.
+ */
+void __sched notrace preempt_schedule_context(void)
+{
+ struct thread_info *ti = current_thread_info();
+ enum ctx_state prev_ctx;
+
+ if (likely(ti->preempt_count || irqs_disabled()))
+ return;
+
+ /*
+ * Need to disable preemption in case user_exit() is traced
+ * and the tracer calls preempt_enable_notrace() causing
+ * an infinite recursion.
+ */
+ preempt_disable_notrace();
+ prev_ctx = exception_enter();
+ preempt_enable_no_resched_notrace();
+
+ preempt_schedule();
+
+ preempt_disable_notrace();
+ exception_exit(prev_ctx);
+ preempt_enable_notrace();
+}
+EXPORT_SYMBOL_GPL(preempt_schedule_context);
+#endif /* CONFIG_PREEMPT */
/**
* user_exit - Inform the context tracking that the CPU is
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e1a27f9..e8b3350 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -633,7 +633,19 @@ void wake_up_nohz_cpu(int cpu)
static inline bool got_nohz_idle_kick(void)
{
int cpu = smp_processor_id();
- return idle_cpu(cpu) && test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
+
+ if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)))
+ return false;
+
+ if (idle_cpu(cpu) && !need_resched())
+ return true;
+
+ /*
+ * We can't run Idle Load Balance on this CPU for this time so we
+ * cancel it and clear NOHZ_BALANCE_KICK
+ */
+ clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
+ return false;
}
#else /* CONFIG_NO_HZ_COMMON */
@@ -1393,8 +1405,9 @@ static void sched_ttwu_pending(void)
void scheduler_ipi(void)
{
- if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()
- && !tick_nohz_full_cpu(smp_processor_id()))
+ if (llist_empty(&this_rq()->wake_list)
+ && !tick_nohz_full_cpu(smp_processor_id())
+ && !got_nohz_idle_kick())
return;
/*
@@ -1417,7 +1430,7 @@ void scheduler_ipi(void)
/*
* Check if someone kicked us for doing the nohz idle load balance.
*/
- if (unlikely(got_nohz_idle_kick() && !need_resched())) {
+ if (unlikely(got_nohz_idle_kick())) {
this_rq()->idle_balance = 1;
raise_softirq_irqoff(SCHED_SOFTIRQ);
}
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