From: Namhyung Kim <namhyung@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Michael Petlan <mpetlan@redhat.com>,
Wade Mealing <wmealing@redhat.com>
Subject: Re: [PATCH] perf: Fix race in perf_mmap_close function
Date: Mon, 14 Sep 2020 21:48:43 +0900 [thread overview]
Message-ID: <CAM9d7cicyzZvkrXTvSrGrOE626==myvF2hnuUNiUoLXiOKHB+A@mail.gmail.com> (raw)
In-Reply-To: <20200911074931.GA1714160@krava>
On Fri, Sep 11, 2020 at 4:49 PM Jiri Olsa <jolsa@redhat.com> wrote:
> ugh, that's right.. how about change below
Acked-by: Namhyung Kim <namhyung@kernel.org>
Thanks
Namhyung
>
> jirka
>
>
> ---
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 7ed5248f0445..8ab2400aef55 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -5868,11 +5868,11 @@ static void perf_pmu_output_stop(struct perf_event *event);
> static void perf_mmap_close(struct vm_area_struct *vma)
> {
> struct perf_event *event = vma->vm_file->private_data;
> -
> struct perf_buffer *rb = ring_buffer_get(event);
> struct user_struct *mmap_user = rb->mmap_user;
> int mmap_locked = rb->mmap_locked;
> unsigned long size = perf_data_size(rb);
> + bool detach_rest = false;
>
> if (event->pmu->event_unmapped)
> event->pmu->event_unmapped(event, vma->vm_mm);
> @@ -5903,7 +5903,8 @@ static void perf_mmap_close(struct vm_area_struct *vma)
> mutex_unlock(&event->mmap_mutex);
> }
>
> - atomic_dec(&rb->mmap_count);
> + if (atomic_dec_and_test(&rb->mmap_count))
> + detach_rest = true;
>
> if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex))
> goto out_put;
> @@ -5912,7 +5913,7 @@ static void perf_mmap_close(struct vm_area_struct *vma)
> mutex_unlock(&event->mmap_mutex);
>
> /* If there's still other mmap()s of this buffer, we're done. */
> - if (atomic_read(&rb->mmap_count))
> + if (!detach_rest)
> goto out_put;
>
> /*
>
next prev parent reply other threads:[~2020-09-14 12:53 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-10 10:41 [PATCH] perf: Fix race in perf_mmap_close function Jiri Olsa
2020-09-10 13:48 ` Namhyung Kim
2020-09-10 14:47 ` Jiri Olsa
2020-09-11 3:05 ` Namhyung Kim
2020-09-11 7:49 ` Jiri Olsa
2020-09-14 12:48 ` Namhyung Kim [this message]
2020-09-14 20:59 ` Jiri Olsa
2020-09-15 15:35 ` Michael Petlan
2020-09-16 11:53 ` [PATCHv2] " Jiri Olsa
2020-09-16 13:54 ` peterz
2020-09-16 14:38 ` Jiri Olsa
2020-09-16 14:05 ` peterz
2020-10-12 11:45 ` [tip: perf/core] perf/core: Fix race in the perf_mmap_close() function tip-bot2 for Jiri Olsa
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