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Commit 47e9766d authored by Mika Kuoppala's avatar Mika Kuoppala Committed by Daniel Vetter
Browse files

drm/i915: Fix timeout with missed interrupts in __wait_seqno 



Commit 094f9a54 ("drm/i915: Fix __wait_seqno to use true infinite
timeouts") added support for __wait_seqno to detect missing interrupts and
go around them by polling. As there is also timeout detection in
__wait_seqno, the polling and timeout detection were done with the same
timer.

When there has been missed interrupts and polling is needed, the timer is
set to trigger in (now + 1) jiffies in future, instead of the caller
specified timeout.

Now when io_schedule() returns, we calculate the jiffies left to timeout
using the timer expiration value. As the current jiffies is now bound to be
always equal or greater than the expiration value, the timeout_jiffies will
become zero or negative and we return -ETIME to caller even tho the
timeout was never reached.

Fix this by decoupling timeout calculation from timer expiration.

v2: Commit message with some sense in it (Chris Wilson)

v3: add parenthesis on timeout_expire calculation

v4: don't read jiffies without timeout (Chris Wilson)

Signed-off-by: default avatarMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent f9dcb0df

drivers/gpu/drm/i915/i915_gem.c

+6 −8
Original line number Diff line number Diff line
@@ -1017,7 +1017,7 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno, 
	drm_i915_private_t *dev_priv = ring->dev->dev_private;

	struct timespec before, now;

	DEFINE_WAIT(wait);

	long timeout_jiffies;

	unsigned long timeout_expire;

	int ret;



	WARN(dev_priv->pc8.irqs_disabled, "IRQs disabled\n");
@@ -1025,7 +1025,7 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno, 
	if (i915_seqno_passed(ring->get_seqno(ring, true), seqno))

		return 0;



	timeout_jiffies = timeout ? timespec_to_jiffies_timeout(timeout) : 1;

	timeout_expire = timeout ? jiffies + timespec_to_jiffies_timeout(timeout) : 0;



	if (dev_priv->info->gen >= 6 && can_wait_boost(file_priv)) {

		gen6_rps_boost(dev_priv);
@@ -1044,7 +1044,6 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno, 
	getrawmonotonic(&before);

	for (;;) {

		struct timer_list timer;

		unsigned long expire;



		prepare_to_wait(&ring->irq_queue, &wait,

				interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
@@ -1070,23 +1069,22 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno, 
			break;

		}



		if (timeout_jiffies <= 0) {

		if (timeout && time_after_eq(jiffies, timeout_expire)) {

			ret = -ETIME;

			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 = jiffies + (missed_irq(dev_priv, ring) ? 1: timeout_jiffies);

			expire = missed_irq(dev_priv, ring) ? jiffies + 1 : timeout_expire;

			mod_timer(&timer, expire);

		}



		io_schedule();



		if (timeout)

			timeout_jiffies = expire - jiffies;



		if (timer.function) {

			del_singleshot_timer_sync(&timer);

			destroy_timer_on_stack(&timer);