Re: [PATCH] drm/i915: Always normalize return timeout for wait_timeout_ioctl

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Apr 09, 2013 at 10:13:23AM +0100, Chris Wilson wrote:
> As we recompute the remaining timeout after waiting, there is a
> potential for that timeout to be less than zero and so need sanitizing.
> The timeout is always returned to userspace and validated, so we should
> always perform the sanitation.
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Ben Widawsky <ben@bwidawsk.net>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_gem.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 63c05dd..fcf8492 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1045,6 +1045,7 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
>  	if (timeout) {
>  		struct timespec sleep_time = timespec_sub(now, before);
>  		*timeout = timespec_sub(*timeout, sleep_time);
> +		set_normalized_timespec(timeout, 0, 0);

This will just set timeout = {0,0}, no?

And timespec_sub() should already return a normalized timespec, so I
guess the warning would just trigger when sleep_time > timeout. So we
should maybe just check for that case, and only then set timeout={0,0}?

>  	}
>  
>  	switch (end) {
> @@ -1053,8 +1054,6 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
>  	case -ERESTARTSYS: /* Signal */
>  		return (int)end;
>  	case 0: /* Timeout */
> -		if (timeout)
> -			set_normalized_timespec(timeout, 0, 0);
>  		return -ETIME;
>  	default: /* Completed */
>  		WARN_ON(end < 0); /* We're not aware of other errors */
> -- 
> 1.7.10.4

-- 
Ville Syrjälä
Intel OTC