LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Jiri Olsa <jolsa@redhat.com>
To: Namhyung Kim <namhyung@kernel.org>
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 22:59:36 +0200
Message-ID: <20200914205936.GD1714160@krava> (raw)
In-Reply-To: <CAM9d7cicyzZvkrXTvSrGrOE626==myvF2hnuUNiUoLXiOKHB+A@mail.gmail.com>

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

> 
> 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;
> >
> >         /*
> >
> 


  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-10 10:41 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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200914205936.GD1714160@krava \
    --to=jolsa@redhat.com \
    --cc=a.p.zijlstra@chello.nl \
    --cc=acme@kernel.org \
    --cc=alexander.shishkin@linux.intel.com \
    --cc=jolsa@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=mpetlan@redhat.com \
    --cc=namhyung@kernel.org \
    --cc=wmealing@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git