On Thu, Jul 14, 2016 at 10:59:04AM +0100, Chris Wilson wrote: > On Thu, Jul 14, 2016 at 10:12:17AM +0200, Daniel Vetter wrote: > > On Thu, Jul 14, 2016 at 08:04:19AM +0100, Chris Wilson wrote: > > > vGEM buffers are useful for passing data between software clients and > > > hardware renders. By allowing the user to create and attach fences to > > > the exported vGEM buffers (on the dma-buf), the user can implement a > > > deferred renderer and queue hardware operations like flipping and then > > > signal the buffer readiness (i.e. this allows the user to schedule > > > operations out-of-order, but have them complete in-order). > > > > > > This also makes it much easier to write tightly controlled testcases for > > > dma-buf fencing and signaling between hardware drivers. > > > > > > v2: Don't pretend the fences exist in an ordered timeline, but allocate > > > a separate fence-context for each fence so that the fences are > > > unordered. > > > v3: Make the debug output more interesting, and so the signaled status. > > > > > > Testcase: igt/vgem_basic/dmabuf-fence > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > > Cc: Sean Paul <seanpaul@xxxxxxxxxxxx> > > > Cc: Zach Reizner <zachr@xxxxxxxxxx> > > > Cc: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx> > > > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> > > > Acked-by: Zach Reizner <zachr@xxxxxxxxxx> > > > > One thing I completely forgotten: This allows userspace to hang kernel > > drivers. i915 (and other gpu drivers) can recover using hangcheck, but > > dumber drivers (v4l, if that ever happens) probably never except such a > > case. We've had a similar discusion with the userspace fences exposed in > > sw_fence, and decided to move all those ioctl into debugfs. I think we > > should do the same for this vgem-based debugging of implicit sync. Sorry > > for realizing this this late. > > One of the very tests I make is to ensure that we recover from such a > hang. I don't see the difference between this any of the other ways > userspace can shoot itself (and others) in the foot. So one solution would be to make vgem fences automatically timeout (with a flag for root to override for the sake of testing hang detection). -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
