On Thu, 24 May 2012 20:18:04 -0700, Ben Widawsky <ben at bwidawsk.net> wrote: > On Thu, 24 May 2012 15:03:10 -0700 > Ben Widawsky <ben at bwidawsk.net> wrote: > > > This helps implement GL_ARB_sync but stops short of allowing full blown > > sync objects. Finally we can use the new timed seqno waiting function > > to allow userspace to wait on a buffer object with a timeout. This > > implements that interface. > > > > The IOCTL will take as input a buffer object handle, and a timeout in > > nanoseconds (flags is currently optional but will likely be used for > > permutations of flush operations). Users may specify 0 nanoseconds to > > instantly check. > > > > The wait ioctl with a timeout of 0 reimplements the busy ioctl. With any > > non-zero timeout parameter the wait ioctl will wait for the given number > > of nanoseconds on an object becoming unbusy. Since the wait itself does > > so holding struct_mutex the object may become re-busied before this > > completes. A similar but shorter race condition exists in the busy > > ioctl. > > > > v2: ETIME/ERESTARTSYS instead of changing to EBUSY, and EGAIN (Chris) > > Flush the object from the gpu write domain (Chris + Daniel) > > Fix leaked refcount in good case (Chris) > > Naturally align ioctl struct (Chris) > > > > v3: Drop lock after getting seqno to avoid ugly dance (Chris) > > > > v4: check for 0 timeout after olr check to allow polling (Chris) > > > > v5: Updated the comment. (Chris) > > > > v6: Return -ETIME instead of -EBUSY when timeout_ns is 0 (Daniel) > > Fix the commit message comment to be less ugly (Ben) > > Add a warning to check the return timespec (Ben) > > > > v7: Use DRM_AUTH for the ioctl. (Eugeni) So what Ben just reminded me was that we hadn't considered enabling an infinite non-blocking wait through this ioctl. That seems like a gross oversight to me... -Chris -- Chris Wilson, Intel Open Source Technology Centre
