On Fri, Jun 03, 2016 at 05:08:34PM +0100, Chris Wilson wrote:
> We can forgo queuing the hangcheck from the start of every request to
> until we wait upon a request. This reduces the overhead of every
> request, but may increase the latency of detecting a hang. Howeever, if
> nothing every waits upon a hang, did it ever hang? It also improves the
> robustness of the wait-request by ensuring that the hangchecker is
> indeed running before we sleep indefinitely (and thereby ensuring that
> we never actually sleep forever waiting for a dead GPU).
>
> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
I think this will run into TDR patches, where we want a super-low-latency
hangcheck in some cases. But then I think that's implemented by wrapping
the batch in some special cs commands to insta-kill the engine if the
timeout expired, so probably not a big problem. Still worth it to
double-check with Mika I'd say.
-Daniel
> ---
> drivers/gpu/drm/i915/i915_gem.c | 9 +++++----
> drivers/gpu/drm/i915/i915_irq.c | 10 ++++------
> 2 files changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c7a67a7412cd..03256f096ab6 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1310,6 +1310,9 @@ int __i915_wait_request(struct drm_i915_gem_request
> *req,
> break;
> }
>
> + /* Ensure that even if the GPU hangs, we get woken up. */
> + i915_queue_hangcheck(dev_priv);
> +
> timer.function = NULL;
> if (timeout || missed_irq(dev_priv, engine)) {
> unsigned long expire;
> @@ -2674,8 +2677,6 @@ void __i915_add_request(struct drm_i915_gem_request
> *request,
> /* Not allowed to fail! */
> WARN(ret, "emit|add_request failed: %d!\n", ret);
>
> - i915_queue_hangcheck(engine->i915);
> -
> queue_delayed_work(dev_priv->wq,
> &dev_priv->mm.retire_work,
> round_jiffies_up_relative(HZ));
> @@ -3019,8 +3020,8 @@ i915_gem_retire_requests(struct drm_i915_private
> *dev_priv)
>
> if (idle)
> mod_delayed_work(dev_priv->wq,
> - &dev_priv->mm.idle_work,
> - msecs_to_jiffies(100));
> + &dev_priv->mm.idle_work,
> + msecs_to_jiffies(100));
>
> return idle;
> }
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 5c7378374ae6..1303d7c034d3 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -3134,10 +3134,10 @@ static void i915_hangcheck_elapsed(struct work_struct
> *work)
> intel_uncore_arm_unclaimed_mmio_detection(dev_priv);
>
> for_each_engine_id(engine, dev_priv, id) {
> + bool busy = waitqueue_active(&engine->irq_queue);
> u64 acthd;
> u32 seqno;
> unsigned user_interrupts;
> - bool busy = true;
>
> semaphore_clear_deadlocks(dev_priv);
>
> @@ -3160,12 +3160,11 @@ static void i915_hangcheck_elapsed(struct work_struct
> *work)
> if (engine->hangcheck.seqno == seqno) {
> if (ring_idle(engine, seqno)) {
> engine->hangcheck.action = HANGCHECK_IDLE;
> - if (waitqueue_active(&engine->irq_queue)) {
> + if (busy) {
> /* Safeguard against driver failure */
> user_interrupts = kick_waiters(engine);
> engine->hangcheck.score += BUSY;
> - } else
> - busy = false;
> + }
> } else {
> /* We always increment the hangcheck score
> * if the ring is busy and still processing
> @@ -3239,9 +3238,8 @@ static void i915_hangcheck_elapsed(struct work_struct
> *work)
> goto out;
> }
>
> + /* Reset timer in case GPU hangs without another request being added */
> if (busy_count)
> - /* Reset timer case chip hangs without another request
> - * being added */
> i915_queue_hangcheck(dev_priv);
>
> out:
> --
> 2.8.1
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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