From: Peter Zijlstra <peterz@infradead.org>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v2] perf/core: fix a possible deadlock scenario
Date: Tue, 24 Jul 2018 11:18:24 +0200 [thread overview]
Message-ID: <20180724091824.GM2494@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAM_iQpXUsVW7a0+_Z_R-k8xGEQBSKd5Oz7j5+z=G1kQHoDfCqQ@mail.gmail.com>
On Mon, Jul 23, 2018 at 06:44:43PM -0700, Cong Wang wrote:
> On Mon, Jul 23, 2018 at 6:35 PM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> >
> > Hi, Peter, Andi
> >
> > While reviewing the deadlock, I find out it looks like we could have the
> > following infinite recursion too:
> >
> > perf_event_account_interrupt()
> > __perf_event_account_interrupt()
> > perf_adjust_period()
> > event->pmu->stop
> > x86_pmu_stop()
> > x86_pmu.disable()
>
> Hmm, x86_pmu_stop() calls __test_and_clear_bit(), so
> we should not call x86_pmu.disable() twice here.
Right, but since we set HES_UPTODATE after calling
x86_perf_event_update() that can in fact recurse.
Now, I don't think that'll be fatal, but it might be good to test that.
If you pick these patches:
https://lkml.kernel.org/r/20170928121823.430053219@infradead.org
use force_early_printk (and actually configure a serial early_printk)
and put a printk() in x86_pmu_stop() and then run the perf_fuzzer or
something to try and reproduce.
But paranoia suggets moving that HES_UPTODATE thing one line up.
> > intel_pmu_disable_event()
> > intel_pmu_pebs_disable()
> > intel_pmu_drain_pebs_buffer()
> > intel_pmu_drain_pebs_nhm()
> > <repeat....>
> >
> > This time is pure hardware events, attr.freq must be non-zero.
> >
> > And, we could enter this infinite recursion in NMI handler too:
> >
> > intel_pmu_handle_irq()
> > perf_event_overflow()
> > __perf_event_overflow()
> > __perf_event_account_interrupt()
> > ....
> >
> > Or this is impossible too?
I'm not sure I see this second one.. can you be a little more specific?
next prev parent reply other threads:[~2018-07-24 9:18 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-16 21:51 [PATCH] perf/core: fix a possible deadlock scenario Cong Wang
2018-07-18 8:19 ` Jiri Olsa
2018-07-18 20:21 ` Cong Wang
2018-07-19 13:28 ` Jiri Olsa
2018-07-19 19:12 ` [PATCH v2] " Cong Wang
2018-07-20 11:52 ` Peter Zijlstra
2018-07-23 23:16 ` Cong Wang
2018-07-24 1:35 ` Cong Wang
2018-07-24 1:44 ` Cong Wang
2018-07-24 9:18 ` Peter Zijlstra [this message]
2018-07-25 18:44 ` Cong Wang
2018-07-24 9:12 ` Peter Zijlstra
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=20180724091824.GM2494@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=acme@kernel.org \
--cc=ak@linux.intel.com \
--cc=alexander.shishkin@linux.intel.com \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=xiyou.wangcong@gmail.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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).