lkml.org 
[lkml]   [2011]   [Mar]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH,RFC] perf: panic due to inclied cpu context task_ctx value
    On 03/28, Peter Zijlstra wrote:
    >
    > --- linux-2.6.orig/kernel/perf_event.c
    > +++ linux-2.6/kernel/perf_event.c
    > @@ -1767,7 +1767,6 @@ static void ctx_sched_out(struct perf_ev
    > struct perf_event *event;
    >
    > raw_spin_lock(&ctx->lock);
    > - perf_pmu_disable(ctx->pmu);
    > ctx->is_active = 0;
    > if (likely(!ctx->nr_events))
    > goto out;
    > @@ -1777,6 +1776,7 @@ static void ctx_sched_out(struct perf_ev
    > if (!ctx->nr_active)
    > goto out;
    >
    > + perf_pmu_disable(ctx->pmu);
    > if (event_type & EVENT_PINNED) {
    > list_for_each_entry(event, &ctx->pinned_groups, group_entry)
    > group_sched_out(event, cpuctx, ctx);
    > @@ -1786,8 +1786,8 @@ static void ctx_sched_out(struct perf_ev
    > list_for_each_entry(event, &ctx->flexible_groups, group_entry)
    > group_sched_out(event, cpuctx, ctx);
    > }
    > -out:
    > perf_pmu_enable(ctx->pmu);
    > +out:
    > raw_spin_unlock(&ctx->lock);

    Yes, thanks.

    Probably this doesn't matter from the perfomance pov, but imho this
    makes the code more understandable. This is important for occasional
    readers like me ;)


    Could you answer another question? It is not immediately clear why
    ctx_sched_in() does not check nr_active != 0 before doing
    ctx_XXX_sched_in(). I guess, the only reason is perf_rotate_context()
    and the similar logic in perf_event_context_sched_in(). If we are
    doing, say, cpu_ctx_sched_out(FLEXIBLE) + cpu_ctx_sched_in(FLEXIBLE)
    then ->nr_active can be zero after cpu_ctx_sched_out().

    Is my understanding correct? Or is there another reason?

    Oleg.



    \
     
     \ /
      Last update: 2011-03-28 18:27    [W:5.269 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site