From: Daniel Vetter <daniel@ffwll.ch>
To: Takashi Iwai <tiwai@suse.de>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm: Make drm_read() more robust against multithreaded races
Date: Mon, 5 Jan 2015 11:18:12 +0100 [thread overview]
Message-ID: <20150105101812.GT2711@phenom.ffwll.local> (raw)
In-Reply-To: <s5hmw725vyc.wl-tiwai@suse.de>
On Fri, Dec 05, 2014 at 09:42:35AM +0100, Takashi Iwai wrote:
> At Thu, 4 Dec 2014 21:03:25 +0000,
> Chris Wilson wrote:
> >
> > The current implementation of drm_read() faces a number of issues:
> >
> > 1. Upon an error, it consumes the event which may lead to the client
> > blocking.
> > 2. Upon an error, it forgets about events already copied
> > 3. If it fails to copy a single event with O_NONBLOCK it falls into a
> > infinite loop of reporting EAGAIN.
> > 3. There is a race between multiple waiters and blocking reads of the
> > events list.
> >
> > Here, we inline drm_dequeue_event() into drm_read() so that we can take
> > the spinlock around the list walking and event copying, and importantly
> > reorder the error handling to avoid the issues above.
> >
> > Cc: Takashi Iwai <tiwai@suse.de>
>
> Reviewed-by: Takashi Iwai <tiwai@suse.de>
Merged to drm-misc with the tag for the drm_read testcase added. Thanks
for the patch&reivew.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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next prev parent reply other threads:[~2015-01-05 10:18 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <s5hk327pd5w.wl-tiwai@suse.de>
2014-12-04 21:03 ` [PATCH] drm: Make drm_read() more robust against multithreaded races Chris Wilson
2014-12-05 2:19 ` shuang.he
2014-12-05 20:59 ` Daniel Vetter
2014-12-05 8:42 ` Takashi Iwai
2015-01-05 10:18 ` Daniel Vetter [this message]
2014-12-05 8:44 ` [Intel-gfx] " Daniel Vetter
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