Groups > linux.kernel > #1732046

Re: [patch V2 00/29] lockup_detector: Cure hotplug deadlocks and replace duct tape

From	Ingo Molnar <mingo@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [patch V2 00/29] lockup_detector: Cure hotplug deadlocks and replace duct tape
Date	2017-09-14 07:30 +0200
Message-ID	<upuSR-Qy-9@gated-at.bofh.it> (permalink)
References	<uoZm2-5w8-5@gated-at.bofh.it> <upkgO-2kQ-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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* Don Zickus <dzickus@redhat.com> wrote:

> On Tue, Sep 12, 2017 at 09:36:54PM +0200, Thomas Gleixner wrote:
> > The lockup detector is broken is several ways:
> > 
> >     - It's deadlock prone vs. CPU hotplug in various ways. Some of these
> >       are due to recursive cpus_read_lock() others are due to
> >       cpus_read_lock() from CPU hotplug callbacks which immediately lock
> >       the machine because cpus are write locked.
> > 
> >     - The handling of the cpu hotplug threads happens sideways to the
> >       smpboot thread infrastructure, which is racy and pointless
> > 
> >     - The handling of the user space sysctl interface is a complete
> >       trainwreck as it fiddles directly with variables which can be
> >       modified or evaluated by the running watchdogs.
> > 
> >     - The perf event initialization is a trainwreck as it tries to create
> >       perf events over and over even if perf is not functional (no
> >       hardware, ....). To avoid excessive dmesg spam it contains magic
> >       printk ratelimiting along with either wrong or useless messages.
> > 
> >     - The code structure is horrible as ifdef sections are scattered all
> >       over the place which makes it unreadable
> > 
> >     - There is more wreckage, but see the changelogs for the ugly details.
> >
> 
> Aside from the simple compile issue in patch 25.  I have no issues with this
> patchset.  Thanks Thomas!
> 
> Reviewed-by: Don Zickus <dzickus@redhat.com>

Thanks guys! I've applied the series and will push it out after some testing.

Thanks,

	Ingo

Thread

[patch V2 00/29] lockup_detector: Cure hotplug deadlocks and replace  duct tape Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 21:50 +0200
  [patch V2 14/29] lockup_detector: Split out cpumask write function Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 21:50 +0200
    [tip:core/urgent] watchdog/core: Split out cpumask write function tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 05/29] lockup_detector: Remove broken suspend/resume  interfaces Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 21:50 +0200
    [tip:core/urgent] watchdog/core: Remove broken suspend/resume  interfaces tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 12:50 +0200
  [patch V2 16/29] lockup_detector: Create new thread handling  infrastructure Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 21:50 +0200
    [tip:core/urgent] watchdog/core: Create new thread handling  infrastructure tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 01/29] hardlockup_detector: Provide interface to  stop/restart perf events Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 21:50 +0200
    [tip:core/urgent] watchdog/hardlockup: Provide interface to  stop/restart perf events tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-09-14 12:50 +0200
  [patch V2 26/29] lockup_detector/perf: Implement CPU enable  replacement Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/hardlockup/perf: Implement CPU enable  replacement tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 06/29] lockup_detector: Rework cpu hotplug locking Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Rework CPU hotplug locking tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 12:50 +0200
  [patch V2 28/29] lockup_detector/perf: Simplify deferred event destroy Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/hardlockup/perf: Simplify deferred event  destroy tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 04/29] parisc: Use lockup_detector_stop() Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    Re: [patch V2 04/29] parisc: Use lockup_detector_stop() Helge Deller <deller@gmx.de> - 2017-09-14 11:10 +0200
      Re: [patch V2 04/29] parisc: Use lockup_detector_stop() Don Zickus <dzickus@redhat.com> - 2017-09-14 15:50 +0200
    [tip:core/urgent] parisc, watchdog/core: Use lockup_detector_stop() tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 12:50 +0200
  [patch V2 17/29] lockup_detector: Get rid of the thread  teardown/setup dance Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Get rid of the thread  teardown/setup dance tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 03/29] lockup_detector: Provide interface to stop from  poweroff() Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Provide interface to stop from  poweroff() tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 12:50 +0200
  [patch V2 10/29] lockup_detector/perf: Prevent cpu hotplug deadlock Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/hardlockup/perf: Prevent CPU hotplug  deadlock tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 12:50 +0200
  [patch V2 13/29] lockup_detector: Cleanup the ifdef maze Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Clean up the #ifdef maze tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 29/29] lockup_detector: Cleanup hotplug locking mess Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/hardlockup: Clean up hotplug locking  mess tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 09/29] lockup_detector/perf: Remove broken self disable on  failure Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/hardlockup/perf: Remove broken self  disable on failure tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 12:50 +0200
  [patch V2 08/29] lockup_detector: Mark hardlockup_detector_disable()  __init Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Mark hardlockup_detector_disable()  __init tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 12:50 +0200
  [patch V2 18/29] lockup_detector: Further simplify sysctl handling Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Further simplify sysctl handling tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 12/29] lockup_detector: Cleanup stub functions Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Clean up stub functions tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 15/29] smpboot/threads: Avoid runtime allocation Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] smpboot/threads, watchdog/core: Avoid runtime  allocation tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 20/29] lockup_detector/sysctl: Get rid of the ifdeffery Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/sysctl: Get rid of the #ifdeffery tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 27/29] lockup_detector: Use new perf CPU enable mechanism Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/hardlockup/perf: Use new perf CPU enable  mechanism tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 24/29] lockup_detector/perf: Implement init time perf  validation Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/hardlockup/perf: Implement init time  perf validation tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 19/29] lockup_detector: Cleanup header mess Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Clean up header mess tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 22/29] lockup_detector: Make watchdog_nmi_reconfigure() two  stage Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core, powerpc: Make  watchdog_nmi_reconfigure() two stage tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 25/29] lockup_detector: Implement init time detection of  perf Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    Re: [patch V2 25/29] lockup_detector: Implement init time detection  of perf Don Zickus <dzickus@redhat.com> - 2017-09-13 20:10 +0200
      Re: [patch V2 25/29] lockup_detector: Implement init time detection  of perf Thomas Gleixner <tglx@linutronix.de> - 2017-09-13 20:10 +0200
        Re: [patch V2 25/29] lockup_detector: Implement init time detection  of perf Ingo Molnar <mingo@kernel.org> - 2017-09-14 07:30 +0200
    [tip:core/urgent] watchdog/hardlockup/perf: Implement init time  detection of perf tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  [patch V2 23/29] lockup_detector: Get rid of the racy update loop Thomas Gleixner <tglx@linutronix.de> - 2017-09-12 22:00 +0200
    [tip:core/urgent] watchdog/core: Get rid of the racy update loop tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-09-14 13:00 +0200
  Re: [patch V2 00/29] lockup_detector: Cure hotplug deadlocks and  replace duct tape Don Zickus <dzickus@redhat.com> - 2017-09-13 20:10 +0200
    Re: [patch V2 00/29] lockup_detector: Cure hotplug deadlocks and  replace duct tape Ingo Molnar <mingo@kernel.org> - 2017-09-14 07:30 +0200
    Re: [patch V2 00/29] lockup_detector: Cure hotplug deadlocks and  replace duct tape Thomas Gleixner <tglx@linutronix.de> - 2017-09-14 10:20 +0200

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