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    Subject[RFC][PATCH 1/7] perf: Fix task refcount issues
    Currently it looks like find_lively_task_by_vpid() takes a task ref
    and relies on find_get_context() to drop it.

    The problem is that perf_event_create_kernel_counter() shouldn't be
    dropping task refs.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Matt Helsley <matthltc@us.ibm.com>
    ---
    kernel/perf_event.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    Index: linux-2.6/kernel/perf_event.c
    ===================================================================
    --- linux-2.6.orig/kernel/perf_event.c
    +++ linux-2.6/kernel/perf_event.c
    @@ -2124,11 +2124,9 @@ find_get_context(struct pmu *pmu, struct
    }
    }

    - put_task_struct(task);
    return ctx;

    errout:
    - put_task_struct(task);
    return ERR_PTR(err);
    }

    @@ -5536,7 +5534,7 @@ SYSCALL_DEFINE5(perf_event_open,
    ctx = find_get_context(pmu, task, cpu);
    if (IS_ERR(ctx)) {
    err = PTR_ERR(ctx);
    - goto err_group_fd;
    + goto err_task;
    }

    /*
    @@ -5632,6 +5630,9 @@ SYSCALL_DEFINE5(perf_event_open,

    err_context:
    put_ctx(ctx);
    +err_task:
    + if (task)
    + put_task_struct(task);
    err_group_fd:
    fput_light(group_file, fput_needed);
    free_event(event);



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