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perf: Cure task_oncpu_function_call() races

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Oleg reported that on architectures with
__ARCH_WANT_INTERRUPTS_ON_CTXSW the IPI from
task_oncpu_function_call() can land before perf_event_task_sched_in()
and cause interesting situations for eg. perf_install_in_context().

This patch reworks the task_oncpu_function_call() interface to give a
more usable primitive as well as rework all its users to hopefully be
more obvious as well as remove the races.

While looking at the code I also found a number of races against
perf_event_task_sched_out() which can flip contexts between tasks so
plug those too.

Reported-and-reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
2011-02-02 13:19:09 +01:00
committed by Ingo Molnar
parent b84defe603
commit fe4b04fa31
3 changed files with 172 additions and 124 deletions
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29
kernel/sched.c
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@@ -2265,27 +2265,6 @@ void kick_process(struct task_struct *p)
EXPORT_SYMBOL_GPL(kick_process);
#endif /* CONFIG_SMP */
/**
* task_oncpu_function_call - call a function on the cpu on which a task runs
* @p: the task to evaluate
* @func: the function to be called
* @info: the function call argument
*
* Calls the function @func when the task is currently running. This might
* be on the current CPU, which just calls the function directly
*/
void task_oncpu_function_call(struct task_struct *p,
void (*func) (void *info), void *info)
{
int cpu;
preempt_disable();
cpu = task_cpu(p);
if (task_curr(p))
smp_call_function_single(cpu, func, info, 1);
preempt_enable();
}
#ifdef CONFIG_SMP
/*
* ->cpus_allowed is protected by either TASK_WAKING or rq->lock held.
@@ -2776,9 +2755,12 @@ static inline void
prepare_task_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
sched_info_switch(prev, next);
perf_event_task_sched_out(prev, next);
fire_sched_out_preempt_notifiers(prev, next);
prepare_lock_switch(rq, next);
prepare_arch_switch(next);
trace_sched_switch(prev, next);
}
/**
@@ -2911,7 +2893,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
struct mm_struct *mm, *oldmm;
prepare_task_switch(rq, prev, next);
trace_sched_switch(prev, next);
mm = next->mm;
oldmm = prev->active_mm;
/*
@@ -3989,9 +3971,6 @@ need_resched_nonpreemptible:
rq->skip_clock_update = 0;
if (likely(prev != next)) {
sched_info_switch(prev, next);
perf_event_task_sched_out(prev, next);
rq->nr_switches++;
rq->curr = next;
++*switch_count;