[Mesa-dev] [PATCH] i965: Fix uint64_t overflow in intel_client_wait_sync()

[Matt Turner]

On Mon, Mar 2, 2015 at 4:27 PM, Kristian Høgsberg <krh at bitplanet.net> wrote:
> DRM_IOCTL_I915_GEM_WAIT takes an int64_t for the timeout value but
> GL_ARB_sync takes an uint64_t.  Further, the ioctl used to wait
> indefinitely when passed a negative timeout, but it's been broken and
> now returns immediately in that case.  Thus, if an application passes
> UINT64_MAX to wait forever, we overflow to -1LL and return immediately.
> Work around this mess by clamping the wait timeout to INT64_MAX.
>
> Signed-off-by: Kristian Høgsberg <krh at bitplanet.net>
> ---
>
>
>  src/mesa/drivers/dri/i965/intel_syncobj.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/src/mesa/drivers/dri/i965/intel_syncobj.c b/src/mesa/drivers/dri/i965/intel_syncobj.c
> index 9cde152..fb95892 100644
> --- a/src/mesa/drivers/dri/i965/intel_syncobj.c
> +++ b/src/mesa/drivers/dri/i965/intel_syncobj.c
> @@ -84,6 +84,13 @@ static void intel_client_wait_sync(struct gl_context *ctx, struct gl_sync_object
>  {
>     struct intel_sync_object *sync = (struct intel_sync_object *)s;
>
> +   /* DRM_IOCTL_I915_GEM_WAIT uses a signed 64 bit timeout and returns
> +    * immediately for timeouts <= 0.  The best we can do is to clamp the
> +    * timeout to INT64_MAX.  This limits the maximum timeout from 584 years to
> +    * 292 years - likely not a big deal. */

 */ on its own line.