From 8592e6486a177a02f048567cb928bc3a1f9a86c3 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 2 Dec 2009 12:56:46 +0900 Subject: [PATCH] sched: Revert 498657a478c60be092208422fefa9c7b248729c2 498657a478c60be092208422fefa9c7b248729c2 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 Acked-by: Avi Kivity 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 --- include/linux/preempt.h | 5 +++++ kernel/sched.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 72b1a10a59b6..2e681d9555bd 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -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); diff --git a/kernel/sched.c b/kernel/sched.c index b3d4e2be95aa..1031cae39c4c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -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)) { -- 2.34.1