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Commit 8592e648 authored Dec 02, 2009 by Tejun Heo Committed by Ingo Molnar Dec 02, 2009

sched: Revert 498657a4



498657a4 incorrectly assumed
that preempt wasn't disabled around context_switch() and thus
was fixing imaginary problem.  It also broke KVM because it
depended on ->sched_in() to be called with irq enabled so that
it can do smp calls from there.

Revert the incorrect commit and add comment describing different
contexts under with the two callbacks are invoked.

Avi: spotted transposed in/out in the added comment.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Avi Kivity <avi@redhat.com>
Cc: peterz@infradead.org
Cc: efault@gmx.de
Cc: rusty@rustcorp.com.au
LKML-Reference: <1259726212-30259-2-git-send-email-tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent b7b20df9

include/linux/preempt.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -105,6 +105,11 @@ struct preempt_notifier;
		* @sched_out: we've just been preempted
		* notifier: struct preempt_notifier for the task being preempted
		* next: the task that's kicking us out
		*
		* Please note that sched_in and out are called under different
		* contexts. sched_out is called with rq lock held and irq disabled
		* while sched_in is called without rq lock and irq enabled. This
		* difference is intentional and depended upon by its users.
		*/
		struct preempt_ops {
		void (sched_in)(struct preempt_notifier notifier, int cpu);

kernel/sched.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2768,9 +2768,9 @@ static void finish_task_switch(struct rq rq, struct task_struct prev)
		prev_state = prev->state;
		finish_arch_switch(prev);
		perf_event_task_sched_in(current, cpu_of(rq));
		fire_sched_in_preempt_notifiers(current);
		finish_lock_switch(rq, prev);

		fire_sched_in_preempt_notifiers(current);
		if (mm)
		mmdrop(mm);
		if (unlikely(prev_state == TASK_DEAD)) {