linux-kernel - Re: [PATCH] drm/msm: return fence_fd = -1 if gem

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Date:   Mon, 12 Dec 2016 19:23:25 -0200
From:   Gustavo Padovan <gustavo.padovan@...labora.com>
To:     Chris Wilson <chris@...is-wilson.co.uk>,
        Gustavo Padovan <gustavo@...ovan.org>,
        dri-devel@...ts.freedesktop.org,
        Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <freedreno@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/msm: return fence_fd = -1 if gem_submit fails

2016-12-12 Chris Wilson <chris@...is-wilson.co.uk>:

> On Mon, Dec 12, 2016 at 05:41:08PM -0200, Gustavo Padovan wrote:
> > From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> > 
> > Previously we were returning garbage here, fix it by setting it to -1
> > before the first possible point of failure.
> 
> The convention is that on error paths you do not modify user inputs. In
> particular, consider EINTR where the usual pattern (e.g. drmIoctl) is
> 
> 	do {
> 		err = ioctl(fd, SUBMIT, arg);
> 	} while (err == -EINTR);
> 
> If you modify the in fence before you consume it, you can't recreate it
> after handling the signal.

Right. I didn't know about that convention. So maybe we let it as is. :)

Gustavo