From: Thomas Gleixner <tglx@linutronix.de>
To: Don Zickus <dzickus@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Borislav Petkov <bp@alien8.de>,
Sebastian Siewior <bigeasy@linutronix.de>,
Nicholas Piggin <npiggin@gmail.com>,
Chris Metcalf <cmetcalf@mellanox.com>,
Ulrich Obergfell <uobergfe@redhat.com>
Subject: Re: [patch 10/29] lockup_detector/perf: Prevent cpu hotplug deadlock
Date: Fri, 1 Sep 2017 21:29:07 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1709012127430.2372@nanos> (raw)
In-Reply-To: <20170901190208.pn4vq25udylxehph@redhat.com>
On Fri, 1 Sep 2017, Don Zickus wrote:
> On Thu, Aug 31, 2017 at 09:16:08AM +0200, Thomas Gleixner wrote:
> > The following deadlock is possible in the watchdog hotplug code:
> >
> > cpus_write_lock()
> > ...
> > takedown_cpu()
> > smpboot_park_threads()
> > smpboot_park_thread()
> > kthread_park()
> > ->park() := watchdog_disable()
> > watchdog_nmi_disable()
> > perf_event_release_kernel();
> > put_event()
> > _free_event()
> > ->destroy() := hw_perf_event_destroy()
> > x86_release_hardware()
> > release_ds_buffers()
> > get_online_cpus()
> >
> > when a per cpu watchdog perf event is destroyed which drops the last
> > reference to the PMU hardware. The cleanup code there invokes
> > get_online_cpus() which instantly deadlocks because the hotplug percpu
> > rwsem is write locked.
>
> The main reason perf_event_release_kernel is in this path is because the
> oprofile folks complained they couldn't use the perf counters when the
> nmi_watchdog was disabled on the command line.
If the nmi watchdog is disabled on the command line then there are no
counters claimed at all.
Thanks,
tglx
next prev parent reply other threads:[~2017-09-01 19:29 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-31 7:15 [patch 00/29] lockup_detector: Cure hotplug deadlocks and replace duct tape Thomas Gleixner
2017-08-31 7:15 ` [patch 01/29] hardlockup_detector: Provide interface to stop/restart perf events Thomas Gleixner
2017-09-06 16:14 ` Borislav Petkov
2017-08-31 7:16 ` [patch 02/29] perf/x86/intel: Sanitize PMU HT bug workaround Thomas Gleixner
2017-08-31 7:16 ` [patch 03/29] lockup_detector: Provide interface to stop from poweroff() Thomas Gleixner
2017-08-31 7:16 ` [patch 04/29] parisc: Use lockup_detector_stop() Thomas Gleixner
2017-08-31 7:16 ` [patch 05/29] lockup_detector: Remove broken suspend/resume interfaces Thomas Gleixner
2017-08-31 7:16 ` [patch 06/29] lockup_detector: Rework cpu hotplug locking Thomas Gleixner
2017-08-31 7:16 ` [patch 07/29] lockup_detector: Rename watchdog_proc_mutex Thomas Gleixner
2017-08-31 7:16 ` [patch 08/29] lockup_detector: Mark hardlockup_detector_disable() __init Thomas Gleixner
2017-08-31 7:16 ` [patch 09/29] lockup_detector/perf: Remove broken self disable on failure Thomas Gleixner
2017-08-31 7:16 ` [patch 10/29] lockup_detector/perf: Prevent cpu hotplug deadlock Thomas Gleixner
2017-09-01 19:02 ` Don Zickus
2017-09-01 19:29 ` Thomas Gleixner [this message]
2017-09-05 14:51 ` Don Zickus
2017-08-31 7:16 ` [patch 11/29] lockup_detector: Remove park_in_progress hackery Thomas Gleixner
[not found] ` <CAEeg4=CJohPTi8FUNWqb3egsbZnExyJapcNC7wD-2amXTsMrYw@mail.gmail.com>
2017-09-04 12:10 ` Peter Zijlstra
2017-09-05 15:15 ` Don Zickus
2017-09-05 15:42 ` Thomas Gleixner
2017-09-05 13:58 ` Thomas Gleixner
2017-09-05 19:19 ` [patch V2 11/29] lockup_detector: Remove park_in_progress obfuscation Thomas Gleixner
2017-09-14 10:43 ` [tip:core/urgent] watchdog/core: Remove the " tip-bot for Thomas Gleixner
2017-08-31 7:16 ` [patch 12/29] lockup_detector: Cleanup stub functions Thomas Gleixner
2017-08-31 7:16 ` [patch 13/29] lockup_detector: Cleanup the ifdef maze Thomas Gleixner
2017-08-31 7:16 ` [patch 14/29] lockup_detector: Split out cpumask write function Thomas Gleixner
2017-08-31 7:16 ` [patch 15/29] smpboot/threads: Avoid runtime allocation Thomas Gleixner
2017-08-31 7:16 ` [patch 16/29] lockup_detector: Create new thread handling infrastructure Thomas Gleixner
2017-08-31 7:16 ` [patch 17/29] lockup_detector: Get rid of the thread teardown/setup dance Thomas Gleixner
2017-09-01 19:08 ` Don Zickus
2017-09-01 19:45 ` Thomas Gleixner
2017-08-31 7:16 ` [patch 18/29] lockup_detector: Further simplify sysctl handling Thomas Gleixner
2017-08-31 7:16 ` [patch 19/29] lockup_detector: Cleanup header mess Thomas Gleixner
2017-08-31 7:16 ` [patch 20/29] lockup_detector/sysctl: Get rid of the ifdeffery Thomas Gleixner
2017-08-31 7:16 ` [patch 21/29] lockup_detector: Cleanup sysctl variable name space Thomas Gleixner
2017-08-31 7:16 ` [patch 22/29] lockup_detector: Make watchdog_nmi_reconfigure() two stage Thomas Gleixner
2017-08-31 7:16 ` [patch 23/29] lockup_detector: Get rid of the racy update loop Thomas Gleixner
2017-08-31 7:16 ` [patch 24/29] lockup_detector/perf: Implement init time perf validation Thomas Gleixner
2017-09-07 15:58 ` Don Zickus
2017-08-31 7:16 ` [patch 25/29] lockup_detector: Implement init time detection of perf Thomas Gleixner
2017-08-31 7:16 ` [patch 26/29] lockup_detector/perf: Implement CPU enable replacement Thomas Gleixner
2017-08-31 7:16 ` [patch 27/29] lockup_detector: Use new perf CPU enable mechanism Thomas Gleixner
2017-08-31 7:16 ` [patch 28/29] lockup_detector/perf: Simplify deferred event destroy Thomas Gleixner
2017-08-31 7:16 ` [patch 29/29] lockup_detector: Cleanup hotplug locking mess Thomas Gleixner
2017-08-31 22:10 ` [patch 00/29] lockup_detector: Cure hotplug deadlocks and replace duct tape Don Zickus
2017-09-01 4:42 ` Nicholas Piggin
2017-09-01 9:18 ` Thomas Gleixner
2017-09-07 16:04 ` Don Zickus
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=alpine.DEB.2.20.1709012127430.2372@nanos \
--to=tglx@linutronix.de \
--cc=akpm@linux-foundation.org \
--cc=bigeasy@linutronix.de \
--cc=bp@alien8.de \
--cc=cmetcalf@mellanox.com \
--cc=dzickus@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=npiggin@gmail.com \
--cc=peterz@infradead.org \
--cc=uobergfe@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
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).