[Intel-gfx] [PATCH 1/2] drm/i915: Convert hangcheck from a timer into a delayed work item

[Mika Kuoppala]

From: Chris Wilson <chris at chris-wilson.co.uk>

When run as a timer, i915_hangcheck_elapsed() must adhere to all the
rules of running in a softirq context. This is advantageous to us as we
want to minimise the risk that a driver bug will prevent us from
detecting a hung GPU. However, that is irrelevant if the driver bug
prevents us from resetting and recovering. Still it is prudent not to
rely on mutexes inside the checker, but given the coarseness of
dev->struct_mutex doing so is extremely hard.

Give in and run from a work queue, i.e. outside of softirq.

v2:

The conversion does have one significant change, from the use of
mod_timer to schedule_delayed_work, means that the time that we execute
the first hangcheck is fixed and not continually deferred by later work.
This has the advantage of not allowing userspace to fill the ring before
hangcheck can finally run. At the same time, it removes the ability for
the interrupt to defer the hangcheck as well. This is sensible for that
an interrupt is only for a single engine, whereas we perform hangcheck
globally, so whilst one ring may have hung, the other could be running
normally and preventing the hangcheck from firing.

Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Daniel Vetter <dnaiel.vetter at ffwll.chm>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk> (v2)
Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/i915_dma.c |  2 +-
 drivers/gpu/drm/i915/i915_drv.c |  2 +-
 drivers/gpu/drm/i915/i915_drv.h |  2 +-
 drivers/gpu/drm/i915/i915_gem.c |  2 +-
 drivers/gpu/drm/i915/i915_irq.c | 23 +++++++++--------------
 5 files changed, 13 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 51e8fe5..7c64669 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -934,7 +934,7 @@ int i915_driver_unload(struct drm_device *dev)
 	}
 
 	/* Free error state after interrupts are fully disabled. */
-	del_timer_sync(&dev_priv->gpu_error.hangcheck_timer);
+	cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);
 	cancel_work_sync(&dev_priv->gpu_error.work);
 	i915_destroy_error_state(dev);
 
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 66c72bd..cb1468d 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1396,7 +1396,7 @@ static int intel_runtime_suspend(struct device *device)
 		return ret;
 	}
 
-	del_timer_sync(&dev_priv->gpu_error.hangcheck_timer);
+	cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);
 	intel_uncore_forcewake_reset(dev, false);
 	dev_priv->pm.suspended = true;
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 0d67b17..ce2acdd 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1345,7 +1345,7 @@ struct i915_gpu_error {
 	/* Hang gpu twice in this window and your context gets banned */
 #define DRM_I915_CTX_BAN_PERIOD DIV_ROUND_UP(8*DRM_I915_HANGCHECK_PERIOD, 1000)
 
-	struct timer_list hangcheck_timer;
+	struct delayed_work hangcheck_work;
 
 	/* For reset and error_state handling. */
 	spinlock_t lock;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index fc81889..8a178cd 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4615,7 +4615,7 @@ i915_gem_suspend(struct drm_device *dev)
 	i915_gem_stop_ringbuffers(dev);
 	mutex_unlock(&dev->struct_mutex);
 
-	del_timer_sync(&dev_priv->gpu_error.hangcheck_timer);
+	cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);
 	cancel_delayed_work_sync(&dev_priv->mm.retire_work);
 	flush_delayed_work(&dev_priv->mm.idle_work);
 
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 25b2299..a188c7d 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2980,10 +2980,12 @@ ring_stuck(struct intel_engine_cs *ring, u64 acthd)
  * we kick the ring. If we see no progress on three subsequent calls
  * we assume chip is wedged and try to fix it by resetting the chip.
  */
-static void i915_hangcheck_elapsed(unsigned long data)
+static void i915_hangcheck_elapsed(struct work_struct *work)
 {
-	struct drm_device *dev = (struct drm_device *)data;
-	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct drm_i915_private *dev_priv =
+		container_of(work, typeof(*dev_priv),
+			     gpu_error.hangcheck_work.work);
+	struct drm_device *dev = dev_priv->dev;
 	struct intel_engine_cs *ring;
 	int i;
 	int busy_count = 0, rings_hung = 0;
@@ -3097,17 +3099,11 @@ static void i915_hangcheck_elapsed(unsigned long data)
 
 void i915_queue_hangcheck(struct drm_device *dev)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct timer_list *timer = &dev_priv->gpu_error.hangcheck_timer;
-
 	if (!i915.enable_hangcheck)
 		return;
 
-	/* Don't continually defer the hangcheck, but make sure it is active */
-	if (timer_pending(timer))
-		return;
-	mod_timer(timer,
-		  round_jiffies_up(jiffies + DRM_I915_HANGCHECK_JIFFIES));
+	schedule_delayed_work(&to_i915(dev)->gpu_error.hangcheck_work,
+			      round_jiffies_up_relative(DRM_I915_HANGCHECK_JIFFIES));
 }
 
 static void ibx_irq_reset(struct drm_device *dev)
@@ -4351,9 +4347,8 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
 	else
 		dev_priv->pm_rps_events = GEN6_PM_RPS_EVENTS;
 
-	setup_timer(&dev_priv->gpu_error.hangcheck_timer,
-		    i915_hangcheck_elapsed,
-		    (unsigned long) dev);
+	INIT_DELAYED_WORK(&dev_priv->gpu_error.hangcheck_work,
+			  i915_hangcheck_elapsed);
 	INIT_DELAYED_WORK(&dev_priv->hotplug_reenable_work,
 			  intel_hpd_irq_reenable_work);
 
-- 
1.9.1