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    Subject[PATCH] perf: do not set task_ctx pointer in cpuctx if there is no events in the context
    Do not set task_ctx pointer during sched_in if there is no
    events associated with the context. Otherwise if during task
    execution total number of events in the system will become zero
    perf_event_context_sched_out() will not be called and cpuctx->task_ctx
    will be left with a stale value.

    Signed-off-by: Gleb Natapov <gleb@redhat.com>
    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 0f85778..68b13ee 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -2172,7 +2172,8 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx,

    perf_event_sched_in(cpuctx, ctx, task);

    - cpuctx->task_ctx = ctx;
    + if (ctx->nr_events)
    + cpuctx->task_ctx = ctx;

    perf_pmu_enable(ctx->pmu);
    perf_ctx_unlock(cpuctx, ctx);
    --
    Gleb.

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