[Intel-gfx] [PATCH 3/4 v7] drm/i915: wait render timeout ioctl

[Ben Widawsky]

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)

Please take v6 if you don't want the DRM_AUTH change.

Thanks.
Ben