linux-kernel - Re: [Intel-gfx] BUG: sleeping function called from invalid context on 3.10.10-rt7

Open Source and information security mailing list archives

Date:	Thu, 26 Sep 2013 18:16:47 +0200
From:	Mario Kleiner <mario.kleiner.de@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Mario Kleiner <mario.kleiner@...bingen.mpg.de>,
	Peter Hurley <peter@...leysoftware.com>,
	Clark Williams <williams@...hat.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	Dave Airlie <airlied@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Ville Syrjälä <ville.syrjala@...ux.intel.com>
Subject: Re: [Intel-gfx] BUG: sleeping function called from invalid context
 on 3.10.10-rt7

On 25.09.13 16:13, Steven Rostedt wrote:
> On Wed, 25 Sep 2013 06:32:10 +0200
> Mario Kleiner <mario.kleiner@...bingen.mpg.de> wrote:
>
>
>> But given the new situation, your proposal is great! If we push the
>> clock readouts into the get_scanoutpos routine, we can make this robust
>> without causing grief for the rt people and without the need for a new
>> separate lock for display regs in intel-kms.
>>
>> E.g., for intel-kms:
>>
>> i915_get_crtc_scanoutpos(..., ktime_t *stime, ktime_t *etime)
>> {
>>     ...
>>     spin_lock_irqsave(...uncore.lock);
>>     preempt_disable();
>>     *stime = ktime_get();
>>     position = __raw_i915_read32(dev_priv, PIPEDSL(pipe));
>>     *etime = ktime_get();
>>     preempt_enable();
>>     spin_unlock_irqrestore(...uncore.lock)
>>     ...
>> }
>>
>> With your patchset to reduce the amount of register reads needed in that
>> function, and given that forcewake handling isn't needed for these
>> registers, this should make it robust again and wouldn't need new locks.
>>
>> Unless ktime_get is also a bad thing to do in a preempt disabled section?
>
> ktime_get() works fine in preempt_disable sections, although it may add
> some latencies, but you shouldn't need to worry about it.
>
> I like this solution the best too, but if it does go in, I would ask to
> send us the patch for adding the preempt_disable() and we can add the
> preempt_disable_rt() to it. Why make mainline have a little more
> overhead?
>
> -- Steve

Good! I will do that. Thanks for clarifying the irq and constraints on 
raw locks in the other thread.

-mario

> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>

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