linux-kernel - Re: WARNING: /usr/projects/linux/linux/drivers/gpu/drm/i915/intel_pm.c:6585 intel_display_power

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Message-ID: <CAPM=9txGrrqYPg9EbpC+9OAB5VCt36vWFRMmoAOvJZV-RSQ2-A@mail.gmail.com>
Date:	Mon, 8 Dec 2014 12:32:01 +1000
From:	Dave Airlie <airlied@...il.com>
To:	"Theodore Ts'o" <tytso@....edu>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jani Nikula <jani.nikula@...el.com>
Subject: Re: WARNING: /usr/projects/linux/linux/drivers/gpu/drm/i915/intel_pm.c:6585
 intel_display_power_put+0x4b/0x116 [i915]()

On 8 December 2014 at 10:34, Theodore Ts'o <tytso@....edu> wrote:
> This is an update to a problem which I reported several months ago
> (see below).  The symptoms have changed a bit since then, but they've
> stablized since 3.17 and 3.18-rcX, and while annoying, it's tolerable,
> so I've been living with it.
>
> What I'm basically seeing now is that any external monitor (either a
> Dell 30" or Dell 24") will be seen after a reboot or a restart of the
> X server.  But if suspend the laptop, disconnect from the dock, and
> resume, and then later on, reconnect to the dock, the external
> monitors are not visible until I kill and restart the X server.
> Another part of the symptom is when I try to probe for the monitors,
> using either xrandr or xfce4-display-settings, the system freezes for
> a second or two, and then when it recovers, if I look in the logs, I
> see the following warning message, repeated twice:

I suspect a lot of the problems are just that xfce isn't sufficiently handling
randr events, and it is getting out of sync, it is like hotplug networking
before NetworkManager etc.

I just tried using XFCE from F21 and if I leave the display settings app
open it crashes hard when I tried the cycle above, which didn't lend
me much confidence, it also never reenabled the monitor when it came
back,

I've tried a few cycles of this with GNOME desktop and it seems to
work pretty well.

I'll try reproducing the exact problem you are seeing however,

I haven't managed that with drm-next tree which has v3.18 merged now.

The i915 driver also has a tendency to WARN_ON on pointless things,
the i915 developers insist these are actual bugs, but don't insist on producing
patches to fix them in a reasonable time frame or if they do, they add
5 more WARN_ONs to compensate.

Dave.
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