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    SubjectRe: [RFC][PATCH 2/9] perf: Clean up ctx reference counting
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    On Sun, 2011-04-10 at 03:17 +0800, Peter Zijlstra wrote:
    > Small cleanup to how we refcount in find_get_context(), this also
    > allows us to use put_ctx() to free things instead of using kfree().
    >
    > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > ---
    > kernel/perf_event.c | 10 +++-------
    > 1 file changed, 3 insertions(+), 7 deletions(-)
    >
    > Index: linux-2.6/kernel/perf_event.c
    > ===================================================================
    > --- linux-2.6.orig/kernel/perf_event.c
    > +++ linux-2.6/kernel/perf_event.c
    > @@ -2831,16 +2831,12 @@ find_get_context(struct pmu *pmu, struct
    > unclone_ctx(ctx);
    > ++ctx->pin_count;
    > raw_spin_unlock_irqrestore(&ctx->lock, flags);
    > - }
    > -
    > - if (!ctx) {
    > + } else {
    > ctx = alloc_perf_context(pmu, task);
    > err = -ENOMEM;
    > if (!ctx)
    > goto errout;
    >
    > - get_ctx(ctx);
    > -
    > err = 0;
    > mutex_lock(&task->perf_event_mutex);
    > /*
    > @@ -2852,14 +2848,14 @@ find_get_context(struct pmu *pmu, struct
    > else if (task->perf_event_ctxp[ctxn])
    > err = -EAGAIN;
    > else {
    > + get_ctx(ctx);
    > ++ctx->pin_count;
    > rcu_assign_pointer(task->perf_event_ctxp[ctxn], ctx);
    > }
    > mutex_unlock(&task->perf_event_mutex);
    >
    > if (unlikely(err)) {
    > - put_task_struct(task);
    > - kfree(ctx);
    > + put_ctx(ctx);

    You moved the get_ctx(), so it seems that this put_ctx is missing its
    relevant get_ctx.

    Lin Ming

    >
    > if (err == -EAGAIN)
    > goto retry;
    >
    >
    > --
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