[Intel-gfx] [i-g-t PATCH 2/2] igt/kms_flip: Fix set_dpms called with an idle bo

[Chris Wilson]

On Fri, Mar 24, 2017 at 01:55:00PM +0200, Ander Conselvan De Oliveira wrote:
> On Thu, 2016-12-01 at 11:23 +0000, Chris Wilson wrote:
> > On Thu, Dec 01, 2016 at 12:58:46PM +0200, Abdiel Janulgue wrote:
> > > Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> 
> How is the bug that this commit fixes triggered? Reverting this change seems to
> fix [1] which, if I understand correctly, is caused by the atomic commit of
> set_dpms() to be waiting for the dummy write to the frontbuffer complete, while 
> the spin batch never ends since the test is blocked and so doesn't handle the
> timer signal. 

That is actually a kernel regression (that I'm responsible for). However
it raises a good point that we don't actually want to interrupt the
modeset to handle the signal in this case, otherwise the interrupt
modeset and when it restarts, it will find it doesn't have to wait -
invalidating our test that it can wait for completion. Hmm, that affects
all users.  We want to delegate that task to a thread/child to avoid
interrupting the syscall and perturbing the actual code under test.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre