From: Michael Petlan <mpetlan@redhat.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>, 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>,
Wade Mealing <wmealing@redhat.com>
Subject: Re: [PATCH] perf: Fix race in perf_mmap_close function
Date: Tue, 15 Sep 2020 17:35:20 +0200 (CEST) [thread overview]
Message-ID: <alpine.LRH.2.20.2009151734230.12057@Diego> (raw)
In-Reply-To: <20200914205936.GD1714160@krava>
On Mon, 14 Sep 2020, Jiri Olsa wrote:
> On Mon, Sep 14, 2020 at 09:48:43PM +0900, Namhyung Kim wrote:
> > 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, I'll send full patch after we're done testing this
>
> jirka
I've tested the change and seems OK to me.
Tested-by: Michael Petlan <mpetlan@redhat.com>
>
> >
> > 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:[~2020-09-15 16:26 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
2020-09-14 20:59 ` Jiri Olsa
2020-09-15 15:35 ` Michael Petlan [this message]
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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