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From: Johannes Berg <johannes@sipsolutions.net>
To: "sedat.dilek@gmail.com" <sedat.dilek@gmail.com>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thorsten Leemhuis <thl@ct.de>
Subject: Re: [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() ||
Date: Wed, 17 Aug 2016 19:36:42 +0000	[thread overview]
Message-ID: <1471462602.5173.13.camel@sipsolutions.net> (raw)
In-Reply-To: <CA+icZUWn+zFjCHT+O6ihb7+kQDmn9N3Y588F45_=U=KYHZsoAw@mail.gmail.com>

On Wed, 2016-08-17 at 19:27 +0000, Sedat Dilek wrote:
> 
> > > The call-trace is reproducible with my setup and seen on every
> > > boot.

Might have been nice to keep the backtrace when adding new people :)

I found it here:
https://lists.freedesktop.org/archives/intel-gfx/2016-July/100695.html

> [ CC Peter, Johannes and Thorsten "The regression reporter" ]
> 
> Peter has 2 fixes from Johannes in peterz/queue.git#locking/urgent
> which fix the issue for me.
> 
> [1/2] Revert "drm/fb-helper: Reduce READ_ONCE(master) to
> lockless_dereference"
> [2/2] locking/barriers: suppress sparse warnings in
> lockless_dereference()

I don't see how those could fix it. The second one is a pure compile-
time issue, so it's completely irrelevant - it should not change code
generation in any way.

The first one, reverting to READ_ONCE(), does change the code a bit,
but since lockless_dereference() has no lockdep involvement, I don't
see how that could have any impact on a lockdep report.

Judging from the lockdep report, you have a pretty simple ABBA deadlock
there, but I really don't see how the changes could have any impact.

johannes

WARNING: multiple messages have this Message-ID (diff)
From: Johannes Berg <johannes@sipsolutions.net>
To: "sedat.dilek@gmail.com" <sedat.dilek@gmail.com>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thorsten Leemhuis <thl@ct.de>
Subject: Re: [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || __blocking_notifier_call_chain
Date: Wed, 17 Aug 2016 21:36:42 +0200	[thread overview]
Message-ID: <1471462602.5173.13.camel@sipsolutions.net> (raw)
In-Reply-To: <CA+icZUWn+zFjCHT+O6ihb7+kQDmn9N3Y588F45_=U=KYHZsoAw@mail.gmail.com>

On Wed, 2016-08-17 at 19:27 +0000, Sedat Dilek wrote:
> 
> > > The call-trace is reproducible with my setup and seen on every
> > > boot.

Might have been nice to keep the backtrace when adding new people :)

I found it here:
https://lists.freedesktop.org/archives/intel-gfx/2016-July/100695.html

> [ CC Peter, Johannes and Thorsten "The regression reporter" ]
> 
> Peter has 2 fixes from Johannes in peterz/queue.git#locking/urgent
> which fix the issue for me.
> 
> [1/2] Revert "drm/fb-helper: Reduce READ_ONCE(master) to
> lockless_dereference"
> [2/2] locking/barriers: suppress sparse warnings in
> lockless_dereference()

I don't see how those could fix it. The second one is a pure compile-
time issue, so it's completely irrelevant - it should not change code
generation in any way.

The first one, reverting to READ_ONCE(), does change the code a bit,
but since lockless_dereference() has no lockdep involvement, I don't
see how that could have any impact on a lockdep report.

Judging from the lockdep report, you have a pretty simple ABBA deadlock
there, but I really don't see how the changes could have any impact.

johannes
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  reply	other threads:[~2016-08-17 19:36 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-15  6:00 [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || __blocking_notifier_call_chain Sedat Dilek
2016-07-15  8:40 ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || Chris Wilson
2016-07-15  8:40   ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || __blocking_notifier_call_chain Chris Wilson
2016-07-15 10:37   ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || Sedat Dilek
2016-07-15 10:37     ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || __blocking_notifier_call_chain Sedat Dilek
2016-07-15 21:10     ` Sedat Dilek
2016-08-17 19:27   ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || Sedat Dilek
2016-08-17 19:27     ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || __blocking_notifier_call_chain Sedat Dilek
2016-08-17 19:36     ` Johannes Berg [this message]
2016-08-17 19:36       ` Johannes Berg
2016-08-17 20:29       ` Sedat Dilek
2016-08-01 13:33 ` [Intel-gfx] [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_l Jani Nikula
2016-08-01 13:33   ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || __blocking_notifier_call_chain Jani Nikula
2016-08-02 17:47   ` [Intel-gfx] [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_l Sedat Dilek
2016-08-02 17:47     ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || __blocking_notifier_call_chain Sedat Dilek
2016-08-02 19:56     ` Sedat Dilek
2016-08-03  8:42     ` [Intel-gfx] [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_l Jani Nikula
2016-08-03  8:42       ` [drm-intel-nightly] 2016y-07m-14d-21h-13m-02s UTC: locking dependency: drm_modeset_lock_all() || __blocking_notifier_call_chain Jani Nikula
2016-08-03  5:16 ` ✗ Ro.CI.BAT: warning for " Patchwork

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