Thanks for your review Michel! @MAINTAINER, could you please strip the Change-Id when applying. Thanks! On Fri, Aug 13, 2021 at 3:33 AM Michel Dänzer <michel@xxxxxxxxxxx> wrote: > > On 2021-08-12 9:49 p.m., Mark Yacoub wrote: > > From: Mark Yacoub <markyacoub@xxxxxxxxxx> > > > > [Why] > > Userspace should get back a copy of drm_wait_vblank that's been modified > > even when drm_wait_vblank_ioctl returns a failure. > > > > Rationale: > > drm_wait_vblank_ioctl modifies the request and expects the user to read > > it back. When the type is RELATIVE, it modifies it to ABSOLUTE and updates > > the sequence to become current_vblank_count + sequence (which was > > RELATIVE), but now it became ABSOLUTE. > > drmWaitVBlank (in libdrm) expects this to be the case as it modifies > > the request to be Absolute so it expects the sequence to would have been > > updated. > > > > The change is in compat_drm_wait_vblank, which is called by > > drm_compat_ioctl. This change of copying the data back regardless of the > > return number makes it en par with drm_ioctl, which always copies the > > data before returning. > > > > [How] > > Return from the function after everything has been copied to user. > > > > Fixes: IGT:kms_flip::modeset-vs-vblank-race-interruptible > > Tested on ChromeOS Trogdor(msm) > > > > Signed-off-by: Mark Yacoub <markyacoub@xxxxxxxxxxxx> > > Change-Id: I98da279a5f1329c66a9d1e06b88d40b247b51313 > > With the Gerrit Change-Id removed, > > Reviewed-by: Michel Dänzer <mdaenzer@xxxxxxxxxx> > > > -- > Earthling Michel Dänzer | https://redhat.com > Libre software enthusiast | Mesa and X developer
