sched: Revert 498657a478c60be092208422fefa9c7b248729c2 (8592e648) · Commits · 戴 / test

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>

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)) {

Admin message