Re: [PATCH 02/13] drm/i915: Don't need a timer to wake us up

Daniel Vetter
2016-01-11T08:26:29Z

On Fri, Jan 08, 2016 at 11:29:41AM +0000, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>
> Looks like the sleeping loop in __i915_wait_request can be
> simplified by using io_schedule_timeout instead of setting
> up and destroying a timer.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>

io_schedule_timeout was only added in

commit 9cff8adeaa34b5d2802f03f89803da57856b3b72
Author: NeilBrown <neilb@suse.de>
Date: Fri Feb 13 15:49:17 2015 +1100

sched: Prevent recursion in io_schedule()

(well the EXPORT_SYMBOL for it), that was iirc why this was open-coded.
Please add this to your commit message.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
> drivers/gpu/drm/i915/i915_gem.c | 28 ++++++++--------------------
> 1 file changed, 8 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 6c60e04fc09c..de98dc41fb9f 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1135,11 +1135,6 @@ i915_gem_check_wedge(struct i915_gpu_error *error,
> return 0;
> }
>
> -static void fake_irq(unsigned long data)
> -{
> - wake_up_process((struct task_struct *)data);
> -}
> -
> static bool missed_irq(struct drm_i915_private *dev_priv,
> struct intel_engine_cs *ring)
> {
> @@ -1291,7 +1286,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
> }
>
> for (;;) {
> - struct timer_list timer;
> + long sched_timeout;
>
> prepare_to_wait(&ring->irq_queue, &wait, state);
>
> @@ -1321,21 +1316,14 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
> break;
> }
>
> - timer.function = NULL;
> - if (timeout || missed_irq(dev_priv, ring)) {
> - unsigned long expire;
> -
> - setup_timer_on_stack(&timer, fake_irq, (unsigned long)current);
> - expire = missed_irq(dev_priv, ring) ? jiffies + 1 : timeout_expire;
> - mod_timer(&timer, expire);
> - }
> -
> - io_schedule();
> + if (timeout)
> + sched_timeout = timeout_expire - jiffies;
> + else if (missed_irq(dev_priv, ring))
> + sched_timeout = 1;
> + else
> + sched_timeout = MAX_SCHEDULE_TIMEOUT;
>
> - if (timer.function) {
> - del_singleshot_timer_sync(&timer);
> - destroy_timer_on_stack(&timer);
> - }
> + io_schedule_timeout(sched_timeout);
> }
> if (!irq_test_in_progress)
> ring->irq_put(ring);
> --
> 1.9.1
>
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--
Daniel Vetter
Software Engineer, Intel Corporation