From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
To: "Chris Wilson" <chris@chris-wilson.co.uk>,
"Peter Zijlstra" <peterz@infradead.org>,
"Ingo Molnar" <mingo@redhat.com>,
intel-gfx@lists.freedesktop.org,
"Christian König" <christian.koenig@amd.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mutex: Report recursive ww_mutex locking early
Date: Mon, 30 May 2016 13:16:28 +0200 [thread overview]
Message-ID: <1f1bcf7a-e1bc-e105-bcc6-8ca697fa9c4e@linux.intel.com> (raw)
In-Reply-To: <20160530104547.GG30389@nuc-i3427.alporthouse.com>
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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WARNING: multiple messages have this Message-ID (diff)
From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
To: "Chris Wilson" <chris@chris-wilson.co.uk>,
"Peter Zijlstra" <peterz@infradead.org>,
"Ingo Molnar" <mingo@redhat.com>,
intel-gfx@lists.freedesktop.org,
"Christian König" <christian.koenig@amd.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mutex: Report recursive ww_mutex locking early
Date: Mon, 30 May 2016 13:16:28 +0200 [thread overview]
Message-ID: <1f1bcf7a-e1bc-e105-bcc6-8ca697fa9c4e@linux.intel.com> (raw)
In-Reply-To: <20160530104547.GG30389@nuc-i3427.alporthouse.com>
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).
next prev parent reply other threads:[~2016-05-30 11:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-26 8:31 [PATCH] mutex: Do not spin/queue before performing ww_mutex deadlock avoidance Chris Wilson
2016-05-26 8:31 ` Chris Wilson
2016-05-26 9:02 ` ✗ Ro.CI.BAT: warning for " Patchwork
2016-05-26 10:37 ` [PATCH] " Maarten Lankhorst
2016-05-26 10:43 ` Chris Wilson
2016-05-26 10:43 ` Chris Wilson
2016-05-26 11:08 ` Maarten Lankhorst
2016-05-26 20:08 ` [PATCH] mutex: Report recursive ww_mutex locking early Chris Wilson
2016-05-26 20:08 ` Chris Wilson
2016-05-30 7:43 ` Maarten Lankhorst
2016-05-30 9:11 ` Peter Zijlstra
2016-05-30 9:11 ` Peter Zijlstra
2016-05-30 9:43 ` Maarten Lankhorst
2016-05-30 9:43 ` Maarten Lankhorst
2016-05-30 10:27 ` Peter Zijlstra
2016-05-30 10:45 ` Chris Wilson
2016-05-30 11:16 ` Maarten Lankhorst [this message]
2016-05-30 11:16 ` Maarten Lankhorst
2016-06-03 10:46 ` [tip:locking/core] locking/ww_mutex: " tip-bot for Chris Wilson
2016-05-27 5:34 ` ✗ Ro.CI.BAT: warning for mutex: Do not spin/queue before performing ww_mutex deadlock avoidance (rev2) Patchwork
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