The busywait in __i915_spin_request() does not respect pending signals and so may consume the entire timeslice for the task instead of returning to userspace to handle the signal.
Fixes regression from commit 2def4ad99befa25775dd2f714fdd4d92faec6e34 [v4.2] Author: Chris Wilson chris@chris-wilson.co.uk Date: Tue Apr 7 16:20:41 2015 +0100
drm/i915: Optimistically spin for the request completion
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Jens Axboe axboe@kernel.dk Cc; "Rogozhkin, Dmitry V" dmitry.v.rogozhkin@intel.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Tvrtko Ursulin tvrtko.ursulin@linux.intel.com Cc: Eero Tamminen eero.t.tamminen@intel.com Cc: "Rantala, Valtteri" valtteri.rantala@intel.com Cc: stable@kernel.vger.org --- drivers/gpu/drm/i915/i915_gem.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 5cf4a1998273..740530c571d1 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1146,7 +1146,7 @@ static bool missed_irq(struct drm_i915_private *dev_priv, return test_bit(ring->id, &dev_priv->gpu_error.missed_irq_rings); }
-static int __i915_spin_request(struct drm_i915_gem_request *req) +static int __i915_spin_request(struct drm_i915_gem_request *req, int state) { unsigned long timeout;
@@ -1158,6 +1158,9 @@ static int __i915_spin_request(struct drm_i915_gem_request *req) if (i915_gem_request_completed(req, true)) return 0;
+ if (signal_pending_state(state, current)) + break; + if (time_after_eq(jiffies, timeout)) break;
@@ -1197,6 +1200,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, struct drm_i915_private *dev_priv = dev->dev_private; const bool irq_test_in_progress = ACCESS_ONCE(dev_priv->gpu_error.test_irq_rings) & intel_ring_flag(ring); + int state = interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE; DEFINE_WAIT(wait); unsigned long timeout_expire; s64 before, now; @@ -1221,7 +1225,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, before = ktime_get_raw_ns();
/* Optimistic spin for the next jiffie before touching IRQs */ - ret = __i915_spin_request(req); + ret = __i915_spin_request(req, state); if (ret == 0) goto out;
@@ -1233,8 +1237,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, for (;;) { struct timer_list timer;
- prepare_to_wait(&ring->irq_queue, &wait, - interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE); + prepare_to_wait(&ring->irq_queue, &wait, state);
/* We need to check whether any gpu reset happened in between * the caller grabbing the seqno and now ... */ @@ -1252,7 +1255,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, break; }
- if (interruptible && signal_pending(current)) { + if (signal_pending_state(state, current)) { ret = -ERESTARTSYS; break; }