Re: [PATCH 4/5] drm/i915: properly SIGBUS on I/O errors

From: Daniel Vetter <daniel@ffwll.ch>
To: Intel Graphics Development <intel-gfx@lists.freedesktop.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: Re: [PATCH 4/5] drm/i915: properly SIGBUS on I/O errors
Date: Wed, 4 Jul 2012 22:40:28 +0200	[thread overview]
Message-ID: <20120704204028.GH5375@phenom.ffwll.local> (raw)
In-Reply-To: <1341433123-23055-5-git-send-email-daniel.vetter@ffwll.ch>

On Wed, Jul 04, 2012 at 10:18:42PM +0200, Daniel Vetter wrote:
> ... instead of looping endless with no hope of ever serving that
> page-fault. We only need to break out of this loop when the gpu died,
> to run the reset work (and hopefully resurrect it).

To clarify questions Chris raised on irc: This is about handling I/O
errors not from our own code, but e.g. when the disk died when trying to
swap in a gem bo. So this patch remidies the issue that the current
handling only handles gpu-death-induced cases of -EIO. Admittedly, dying
disks are much rarer than hanging gpus ...

I'll add that blurb to the commit.

-Daniel
> 
> This seems to have been lost in:
> 
> commit d9bc7e9f32716901c617e1f0fb6ce0f74f172686
> Author: Chris Wilson <chris@chris-wilson.co.uk>
> Date:   Mon Feb 7 13:09:31 2011 +0000
> 
>     drm/i915: Fix infinite loop regression from 21dd3734
> 
> Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_gem.c |    5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 7d28555..2b54142 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1141,6 +1141,11 @@ unlock:
>  out:
>  	switch (ret) {
>  	case -EIO:
> +		/* If this -EIO is due to a gpu hang, give the reset code a
> +		 * chance to clean up the mess. Otherwise return the proper
> +		 * SIGBUS. */
> +		if (!atomic_read(&dev_priv->mm.wedged))
> +			return VM_FAULT_SIGBUS;
>  	case -EAGAIN:
>  		/* Give the error handler a chance to run and move the
>  		 * objects off the GPU active list. Next time we service the
> -- 
> 1.7.10
> 

-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48