On Fri, May 12, 2017 at 11:40:32AM +0100, Chris Wilson wrote:
> In commit 1fd7e4169954 ("perf/core: Remove perf_cpu_context::unique_pmu"),
> the search for another user of the pmu_cpu_context was removed, and so
> we unconditionally free it during perf_pmu_unregister. This leads to
> random corruption later and a BUG at mm/percpu.c:689.
>
> Fixes: 1fd7e4169954 ("perf/core: Remove perf_cpu_context::unique_pmu")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: David Carrillo-Cisneros <davidcc@xxxxxxxxxx>
> Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.11+
> ---
> kernel/events/core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index aaefaa27e1a6..e62b6207925c 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -9005,7 +9005,8 @@ void perf_pmu_unregister(struct pmu *pmu)
> device_del(pmu->dev);
> put_device(pmu->dev);
> }
> - free_pmu_context(pmu);
> + if (!find_pmu_context(pmu->task_ctx_nr))
Bleh, that find should be under some guard, such as the mutex we held
ealier.
> + free_pmu_context(pmu);
> }
> EXPORT_SYMBOL_GPL(perf_pmu_unregister);
>
> --
> 2.11.0
>
--
Chris Wilson, Intel Open Source Technology Centre