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

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Date:	Wed, 25 Sep 2013 10:18:03 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:	Mario Kleiner <mario.kleiner@...bingen.mpg.de>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Peter Hurley <peter@...leysoftware.com>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Clark Williams <williams@...hat.com>,
	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>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>
Subject: Re: [Intel-gfx] BUG: sleeping function called from invalid context
 on 3.10.10-rt7

On Wed, 25 Sep 2013 10:49:36 +0300
Ville Syrjälä <ville.syrjala@...ux.intel.com> wrote:

 
> The preempt_disable/enable is not needed. The spinlock serves the same
> purpose already.

As stated, that was only for the -rt patch, as spin_lock_irqsave does
not disable preemption nor does it even disable interrupts.

But I agree, the added preempt_disable() should be sent to us to keep
in the -rt patch itself. We really appreciate that you are thinking
about us :-)  But something like this will just confuse the mainline
folks. Having a "preempt_disable_rt()" would make a lot more sense
(which exists in the -rt patch).

> 
> As far as ktime_get(), I've used it from spinlocked/irq disabled sections
> and so far haven't seen it do bad things. But would be nice to get some
> official statement to that effect.

It's just a read seqlock. It may do a few loops to get the correct
time, but it's fine to have in a preempt/irq disabled section.

-- Steve
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