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sched,perf,kvm: Fix preemption condition

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When ran from the sched-out path (preempt_notifier or perf_event),
p->state is irrelevant to determine preemption. You can get preempted
with !task_is_running() just fine.

The right indicator for preemption is if the task is still on the
runqueue in the sched-out path.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210611082838.285099381@infradead.org
This commit is contained in:
Peter Zijlstra 2021-06-11 10:28:13 +02:00
parent b03fbd4ff2
commit 3ba9f93b12
2 changed files with 4 additions and 5 deletions
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7
kernel/events/core.c
View File

@ -8682,13 +8682,12 @@ static void perf_event_switch(struct task_struct *task,
},
};
if (!sched_in && task->state == TASK_RUNNING)
if (!sched_in && task->on_rq) {
switch_event.event_id.header.misc |=
PERF_RECORD_MISC_SWITCH_OUT_PREEMPT;
}
perf_iterate_sb(perf_event_switch_output,
&switch_event,
NULL);
perf_iterate_sb(perf_event_switch_output, &switch_event, NULL);
}
/*

2
virt/kvm/kvm_main.c
View File

@ -5025,7 +5025,7 @@ static void kvm_sched_out(struct preempt_notifier *pn,
{
struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);
if (current->state == TASK_RUNNING) {
if (current->on_rq) {
WRITE_ONCE(vcpu->preempted, true);
WRITE_ONCE(vcpu->ready, true);
}