Re: [PATCH] mutex: Report recursive ww_mutex locking early

From	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mutex: Report recursive ww_mutex locking early
Date	2016-05-30 13:20 +0200
Message-ID	<rEtoJ-3sl-9@gated-at.bofh.it> (permalink)
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Op 30-05-16 om 12:45 schreef Chris Wilson:
> On Mon, May 30, 2016 at 12:27:46PM +0200, Peter Zijlstra wrote:
>> On Mon, May 30, 2016 at 11:43:31AM +0200, Maarten Lankhorst wrote:
>>> Patch not applied, SCHED_RR:
>> ww_mutex isn't RT aware at all; its one of the things I still have on a
>> todo list. Should I look harder at finding time for this?
> The RT usage in the test is to just try and starve the kernel threads
> that may be used behind the atomic modeset - a problem we have
> encountered in the past. Afaik, no one is using ww_mutex from RT in the
> wild, calling the atomic modeset from the RT was just a shortcut to
> having the system fully populated with RT threads. To be more realistic
> we should be using a couple of normal modesetting threads vs a set of RT
> cpu hogs.
Yeah, unfortunately this doesn't work as you intend it to. You'd need to spawn a few more threads at slightly lower priority so when a thread is blocked waiting for acquisition of the mutexes the workqueues still can't run.

ssh is still responsive with the rest running.
> Otoh, i915.ko always draws the ire of rt-linux so ww_mutex is likely to
> be in their sights in the near future (when i915.ko completes its
> transition to full atomic modesetting).

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[PATCH] mutex: Do not spin/queue before performing ww_mutex deadlock avoidance Chris Wilson <chris@chris-wilson.co.uk> - 2016-05-26 10:40 +0200
  Re: [PATCH] mutex: Do not spin/queue before performing ww_mutex  deadlock avoidance Maarten Lankhorst <maarten.lankhorst@linux.intel.com> - 2016-05-26 12:40 +0200
    Re: [PATCH] mutex: Do not spin/queue before performing ww_mutex  deadlock avoidance Chris Wilson <chris@chris-wilson.co.uk> - 2016-05-26 12:50 +0200
      Re: [PATCH] mutex: Do not spin/queue before performing ww_mutex  deadlock avoidance Maarten Lankhorst <maarten.lankhorst@linux.intel.com> - 2016-05-26 13:10 +0200
  [PATCH] mutex: Report recursive ww_mutex locking early Chris Wilson <chris@chris-wilson.co.uk> - 2016-05-26 22:10 +0200
    Re: [PATCH] mutex: Report recursive ww_mutex locking early Maarten Lankhorst <maarten.lankhorst@linux.intel.com> - 2016-05-30 09:50 +0200
      Re: [PATCH] mutex: Report recursive ww_mutex locking early Peter Zijlstra <peterz@infradead.org> - 2016-05-30 11:20 +0200
        Re: [PATCH] mutex: Report recursive ww_mutex locking early Maarten Lankhorst <maarten.lankhorst@linux.intel.com> - 2016-05-30 11:50 +0200
          Re: [PATCH] mutex: Report recursive ww_mutex locking early Peter Zijlstra <peterz@infradead.org> - 2016-05-30 12:30 +0200
            Re: [PATCH] mutex: Report recursive ww_mutex locking early Chris Wilson <chris@chris-wilson.co.uk> - 2016-05-30 12:50 +0200
              Re: [PATCH] mutex: Report recursive ww_mutex locking early Maarten Lankhorst <maarten.lankhorst@linux.intel.com> - 2016-05-30 13:20 +0200

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