On Fri, 2015-11-13 at 08:36 -0700, Jens Axboe wrote:
> Previous patch was obvious pre-coffee crap, this should work for using
> ktime to spin max 1usec.
1us seems a tad low. I doubt the little wooden gears and pulleys of my
core2 Toshiba Satellite lappy can get one loop ground out in a usec :)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 5cf4a1998273..21192e55c33c 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1148,17 +1148,18 @@ static bool missed_irq(struct drm_i915_private *dev_priv,
>
> static int __i915_spin_request(struct drm_i915_gem_request *req)
> {
> - unsigned long timeout;
> + ktime_t timeout;
>
> if (i915_gem_request_get_ring(req)->irq_refcount)
> return -EBUSY;
>
> - timeout = jiffies + 1;
> + timeout = ktime_get();
> + ktime_add_us(timeout, 1);
> while (!need_resched()) {
> if (i915_gem_request_completed(req, true))
> return 0;
>
> - if (time_after_eq(jiffies, timeout))
> + if (ktime_after(ktime_get(), timeout))
> break;
>
> cpu_relax_lowlatency();
>
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