Re: [PATCH] drm/i915: fix wait ioctl with negative timeout

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Oct 13, 2014 at 12:40:48AM +0800, Chia-I Wu wrote:
> On Sun, Oct 12, 2014 at 1:21 AM, Chia-I Wu <olvaffe@gmail.com> wrote:
> 
> > When timeout_ns is negative, it really means to wait indefinitely instead
> > of
> > returning immediately.  But since userspace can no longer rely on that, I
> > am
> > not sure if there is any point fixing it.
> >
> Note that userspace may use GL_TIMEOUT_IGNORED for timeout_ns to wait
> indefinitely.  The macro is defined to
> 
> #define GL_TIMEOUT_IGNORED                0xFFFFFFFFFFFFFFFFull
> 
> Prior to 3.17, the kernel would behave as expected.  But on 3.17, it would
> return immediately with -ETIME if the bo is busy.

That sounds like a regression, for which we need a testcase in igt and a
special-case in our wait ioctl to make sure that we have an infinite
timeout for this input value. Can you please take care of both?

I guess we could also restore the bevahiour for negative timeouts, just
for the sake of it. Would again need a testcase though. Also note that
I've recently refactored the wait ioctl testcase, so adding new subtests
should be a lot easier now.

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch