diff mbox series

[v2] drm/panfrost: Move the GPU reset bits outside the timeout handler

Message ID 20201030105336.764009-1-boris.brezillon@collabora.com
State New, archived
Headers show
Series [v2] drm/panfrost: Move the GPU reset bits outside the timeout handler | expand

Commit Message

Boris Brezillon Oct. 30, 2020, 10:53 a.m. UTC
We've fixed many races in panfrost_job_timedout() but some remain.
Instead of trying to fix it again, let's simplify the logic and move
the reset bits to a separate work scheduled when one of the queue
reports a timeout.

v2:
- Use atomic_cmpxchg() to conditionally schedule the reset work (Steven Privce)

Fixes: 1a11a88cfd9a ("drm/panfrost: Fix job timeout handling")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
---
 drivers/gpu/drm/panfrost/panfrost_device.c |   1 -
 drivers/gpu/drm/panfrost/panfrost_device.h |   6 +-
 drivers/gpu/drm/panfrost/panfrost_job.c    | 127 ++++++++++++---------
 3 files changed, 79 insertions(+), 55 deletions(-)

Comments

Steven Price Oct. 30, 2020, 11:10 a.m. UTC | #1
On 30/10/2020 10:53, Boris Brezillon wrote:
> We've fixed many races in panfrost_job_timedout() but some remain.
> Instead of trying to fix it again, let's simplify the logic and move
> the reset bits to a separate work scheduled when one of the queue
> reports a timeout.
> 
> v2:
> - Use atomic_cmpxchg() to conditionally schedule the reset work (Steven Privce)
> 
> Fixes: 1a11a88cfd9a ("drm/panfrost: Fix job timeout handling")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

LGTM!

Reviewed-by: Steven Price <steven.price@arm.com>

> ---
>   drivers/gpu/drm/panfrost/panfrost_device.c |   1 -
>   drivers/gpu/drm/panfrost/panfrost_device.h |   6 +-
>   drivers/gpu/drm/panfrost/panfrost_job.c    | 127 ++++++++++++---------
>   3 files changed, 79 insertions(+), 55 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index ea8d31863c50..a83b2ff5837a 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> @@ -200,7 +200,6 @@ int panfrost_device_init(struct panfrost_device *pfdev)
>   	struct resource *res;
>   
>   	mutex_init(&pfdev->sched_lock);
> -	mutex_init(&pfdev->reset_lock);
>   	INIT_LIST_HEAD(&pfdev->scheduled_jobs);
>   	INIT_LIST_HEAD(&pfdev->as_lru_list);
>   
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index 140e004a3790..597cf1459b0a 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -106,7 +106,11 @@ struct panfrost_device {
>   	struct panfrost_perfcnt *perfcnt;
>   
>   	struct mutex sched_lock;
> -	struct mutex reset_lock;
> +
> +	struct {
> +		struct work_struct work;
> +		atomic_t pending;
> +	} reset;
>   
>   	struct mutex shrinker_lock;
>   	struct list_head shrinker_list;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index 4902bc6624c8..14c11293791e 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -20,6 +20,8 @@
>   #include "panfrost_gpu.h"
>   #include "panfrost_mmu.h"
>   
> +#define JOB_TIMEOUT_MS 500
> +
>   #define job_write(dev, reg, data) writel(data, dev->iomem + (reg))
>   #define job_read(dev, reg) readl(dev->iomem + (reg))
>   
> @@ -382,19 +384,37 @@ static bool panfrost_scheduler_stop(struct panfrost_queue_state *queue,
>   			drm_sched_increase_karma(bad);
>   		queue->stopped = true;
>   		stopped = true;
> +
> +		/*
> +		 * Set the timeout to max so the timer doesn't get started
> +		 * when we return from the timeout handler (restored in
> +		 * panfrost_scheduler_start()).
> +		 */
> +		queue->sched.timeout = MAX_SCHEDULE_TIMEOUT;
>   	}
>   	mutex_unlock(&queue->lock);
>   
>   	return stopped;
>   }
>   
> +static void panfrost_scheduler_start(struct panfrost_queue_state *queue)
> +{
> +	if (WARN_ON(!queue->stopped))
> +		return;
> +
> +	mutex_lock(&queue->lock);
> +	/* Restore the original timeout before starting the scheduler. */
> +	queue->sched.timeout = msecs_to_jiffies(JOB_TIMEOUT_MS);
> +	drm_sched_start(&queue->sched, true);
> +	queue->stopped = false;
> +	mutex_unlock(&queue->lock);
> +}
> +
>   static void panfrost_job_timedout(struct drm_sched_job *sched_job)
>   {
>   	struct panfrost_job *job = to_panfrost_job(sched_job);
>   	struct panfrost_device *pfdev = job->pfdev;
>   	int js = panfrost_job_get_slot(job);
> -	unsigned long flags;
> -	int i;
>   
>   	/*
>   	 * If the GPU managed to complete this jobs fence, the timeout is
> @@ -415,56 +435,9 @@ static void panfrost_job_timedout(struct drm_sched_job *sched_job)
>   	if (!panfrost_scheduler_stop(&pfdev->js->queue[js], sched_job))
>   		return;
>   
> -	if (!mutex_trylock(&pfdev->reset_lock))
> -		return;
> -
> -	for (i = 0; i < NUM_JOB_SLOTS; i++) {
> -		struct drm_gpu_scheduler *sched = &pfdev->js->queue[i].sched;
> -
> -		/*
> -		 * If the queue is still active, make sure we wait for any
> -		 * pending timeouts.
> -		 */
> -		if (!pfdev->js->queue[i].stopped)
> -			cancel_delayed_work_sync(&sched->work_tdr);
> -
> -		/*
> -		 * If the scheduler was not already stopped, there's a tiny
> -		 * chance a timeout has expired just before we stopped it, and
> -		 * drm_sched_stop() does not flush pending works. Let's flush
> -		 * them now so the timeout handler doesn't get called in the
> -		 * middle of a reset.
> -		 */
> -		if (panfrost_scheduler_stop(&pfdev->js->queue[i], NULL))
> -			cancel_delayed_work_sync(&sched->work_tdr);
> -
> -		/*
> -		 * Now that we cancelled the pending timeouts, we can safely
> -		 * reset the stopped state.
> -		 */
> -		pfdev->js->queue[i].stopped = false;
> -	}
> -
> -	spin_lock_irqsave(&pfdev->js->job_lock, flags);
> -	for (i = 0; i < NUM_JOB_SLOTS; i++) {
> -		if (pfdev->jobs[i]) {
> -			pm_runtime_put_noidle(pfdev->dev);
> -			panfrost_devfreq_record_idle(&pfdev->pfdevfreq);
> -			pfdev->jobs[i] = NULL;
> -		}
> -	}
> -	spin_unlock_irqrestore(&pfdev->js->job_lock, flags);
> -
> -	panfrost_device_reset(pfdev);
> -
> -	for (i = 0; i < NUM_JOB_SLOTS; i++)
> -		drm_sched_resubmit_jobs(&pfdev->js->queue[i].sched);
> -
> -	mutex_unlock(&pfdev->reset_lock);
> -
> -	/* restart scheduler after GPU is usable again */
> -	for (i = 0; i < NUM_JOB_SLOTS; i++)
> -		drm_sched_start(&pfdev->js->queue[i].sched, true);
> +	/* Schedule a reset if there's no reset in progress. */
> +	if (!atomic_cmpxchg(&pfdev->reset.pending, 0, 1))
> +		schedule_work(&pfdev->reset.work);
>   }
>   
>   static const struct drm_sched_backend_ops panfrost_sched_ops = {
> @@ -531,11 +504,59 @@ static irqreturn_t panfrost_job_irq_handler(int irq, void *data)
>   	return IRQ_HANDLED;
>   }
>   
> +static void panfrost_reset(struct work_struct *work)
> +{
> +	struct panfrost_device *pfdev = container_of(work,
> +						     struct panfrost_device,
> +						     reset.work);
> +	unsigned long flags;
> +	unsigned int i;
> +
> +	for (i = 0; i < NUM_JOB_SLOTS; i++) {
> +		/*
> +		 * We want pending timeouts to be handled before we attempt
> +		 * to stop the scheduler. If we don't do that and the timeout
> +		 * handler is in flight, it might have removed the bad job
> +		 * from the list, and we'll lose this job if the reset handler
> +		 * enters the critical section in panfrost_scheduler_stop()
> +		 * before the timeout handler.
> +		 *
> +		 * Timeout is set to max to make sure the timer is not
> +		 * restarted after the cancellation.
> +		 */
> +		pfdev->js->queue[i].sched.timeout = MAX_SCHEDULE_TIMEOUT;
> +		cancel_delayed_work_sync(&pfdev->js->queue[i].sched.work_tdr);
> +		panfrost_scheduler_stop(&pfdev->js->queue[i], NULL);
> +	}
> +
> +	/* All timers have been stopped, we can safely reset the pending state. */
> +	atomic_set(&pfdev->reset.pending, 0);
> +
> +	spin_lock_irqsave(&pfdev->js->job_lock, flags);
> +	for (i = 0; i < NUM_JOB_SLOTS; i++) {
> +		if (pfdev->jobs[i]) {
> +			pm_runtime_put_noidle(pfdev->dev);
> +			panfrost_devfreq_record_idle(&pfdev->pfdevfreq);
> +			pfdev->jobs[i] = NULL;
> +		}
> +	}
> +	spin_unlock_irqrestore(&pfdev->js->job_lock, flags);
> +
> +	panfrost_device_reset(pfdev);
> +
> +	for (i = 0; i < NUM_JOB_SLOTS; i++) {
> +		drm_sched_resubmit_jobs(&pfdev->js->queue[i].sched);
> +		panfrost_scheduler_start(&pfdev->js->queue[i]);
> +	}
> +}
> +
>   int panfrost_job_init(struct panfrost_device *pfdev)
>   {
>   	struct panfrost_job_slot *js;
>   	int ret, j, irq;
>   
> +	INIT_WORK(&pfdev->reset.work, panfrost_reset);
> +
>   	pfdev->js = js = devm_kzalloc(pfdev->dev, sizeof(*js), GFP_KERNEL);
>   	if (!js)
>   		return -ENOMEM;
> @@ -560,7 +581,7 @@ int panfrost_job_init(struct panfrost_device *pfdev)
>   
>   		ret = drm_sched_init(&js->queue[j].sched,
>   				     &panfrost_sched_ops,
> -				     1, 0, msecs_to_jiffies(500),
> +				     1, 0, msecs_to_jiffies(JOB_TIMEOUT_MS),
>   				     "pan_js");
>   		if (ret) {
>   			dev_err(pfdev->dev, "Failed to create scheduler: %d.", ret);
>
Robin Murphy Oct. 30, 2020, 2:29 p.m. UTC | #2
On 2020-10-30 10:53, Boris Brezillon wrote:
[...]
> +	/* Schedule a reset if there's no reset in progress. */
> +	if (!atomic_cmpxchg(&pfdev->reset.pending, 0, 1))

Nit: this could just be a simple xchg with 1 - you don't need the 
compare aspect, since setting it to true when it was already true is 
still harmless ;)

Robin.
Boris Brezillon Nov. 2, 2020, 8:45 a.m. UTC | #3
On Fri, 30 Oct 2020 14:29:32 +0000
Robin Murphy <robin.murphy@arm.com> wrote:

> On 2020-10-30 10:53, Boris Brezillon wrote:
> [...]
> > +	/* Schedule a reset if there's no reset in progress. */
> > +	if (!atomic_cmpxchg(&pfdev->reset.pending, 0, 1))  
> 
> Nit: this could just be a simple xchg with 1 - you don't need the 
> compare aspect, since setting it to true when it was already true is 
> still harmless ;)

Yep, I'll post a new version using atomic_xchg() here.

Thanks,

Boris
diff mbox series

Patch

diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
index ea8d31863c50..a83b2ff5837a 100644
--- a/drivers/gpu/drm/panfrost/panfrost_device.c
+++ b/drivers/gpu/drm/panfrost/panfrost_device.c
@@ -200,7 +200,6 @@  int panfrost_device_init(struct panfrost_device *pfdev)
 	struct resource *res;
 
 	mutex_init(&pfdev->sched_lock);
-	mutex_init(&pfdev->reset_lock);
 	INIT_LIST_HEAD(&pfdev->scheduled_jobs);
 	INIT_LIST_HEAD(&pfdev->as_lru_list);
 
diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
index 140e004a3790..597cf1459b0a 100644
--- a/drivers/gpu/drm/panfrost/panfrost_device.h
+++ b/drivers/gpu/drm/panfrost/panfrost_device.h
@@ -106,7 +106,11 @@  struct panfrost_device {
 	struct panfrost_perfcnt *perfcnt;
 
 	struct mutex sched_lock;
-	struct mutex reset_lock;
+
+	struct {
+		struct work_struct work;
+		atomic_t pending;
+	} reset;
 
 	struct mutex shrinker_lock;
 	struct list_head shrinker_list;
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index 4902bc6624c8..14c11293791e 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -20,6 +20,8 @@ 
 #include "panfrost_gpu.h"
 #include "panfrost_mmu.h"
 
+#define JOB_TIMEOUT_MS 500
+
 #define job_write(dev, reg, data) writel(data, dev->iomem + (reg))
 #define job_read(dev, reg) readl(dev->iomem + (reg))
 
@@ -382,19 +384,37 @@  static bool panfrost_scheduler_stop(struct panfrost_queue_state *queue,
 			drm_sched_increase_karma(bad);
 		queue->stopped = true;
 		stopped = true;
+
+		/*
+		 * Set the timeout to max so the timer doesn't get started
+		 * when we return from the timeout handler (restored in
+		 * panfrost_scheduler_start()).
+		 */
+		queue->sched.timeout = MAX_SCHEDULE_TIMEOUT;
 	}
 	mutex_unlock(&queue->lock);
 
 	return stopped;
 }
 
+static void panfrost_scheduler_start(struct panfrost_queue_state *queue)
+{
+	if (WARN_ON(!queue->stopped))
+		return;
+
+	mutex_lock(&queue->lock);
+	/* Restore the original timeout before starting the scheduler. */
+	queue->sched.timeout = msecs_to_jiffies(JOB_TIMEOUT_MS);
+	drm_sched_start(&queue->sched, true);
+	queue->stopped = false;
+	mutex_unlock(&queue->lock);
+}
+
 static void panfrost_job_timedout(struct drm_sched_job *sched_job)
 {
 	struct panfrost_job *job = to_panfrost_job(sched_job);
 	struct panfrost_device *pfdev = job->pfdev;
 	int js = panfrost_job_get_slot(job);
-	unsigned long flags;
-	int i;
 
 	/*
 	 * If the GPU managed to complete this jobs fence, the timeout is
@@ -415,56 +435,9 @@  static void panfrost_job_timedout(struct drm_sched_job *sched_job)
 	if (!panfrost_scheduler_stop(&pfdev->js->queue[js], sched_job))
 		return;
 
-	if (!mutex_trylock(&pfdev->reset_lock))
-		return;
-
-	for (i = 0; i < NUM_JOB_SLOTS; i++) {
-		struct drm_gpu_scheduler *sched = &pfdev->js->queue[i].sched;
-
-		/*
-		 * If the queue is still active, make sure we wait for any
-		 * pending timeouts.
-		 */
-		if (!pfdev->js->queue[i].stopped)
-			cancel_delayed_work_sync(&sched->work_tdr);
-
-		/*
-		 * If the scheduler was not already stopped, there's a tiny
-		 * chance a timeout has expired just before we stopped it, and
-		 * drm_sched_stop() does not flush pending works. Let's flush
-		 * them now so the timeout handler doesn't get called in the
-		 * middle of a reset.
-		 */
-		if (panfrost_scheduler_stop(&pfdev->js->queue[i], NULL))
-			cancel_delayed_work_sync(&sched->work_tdr);
-
-		/*
-		 * Now that we cancelled the pending timeouts, we can safely
-		 * reset the stopped state.
-		 */
-		pfdev->js->queue[i].stopped = false;
-	}
-
-	spin_lock_irqsave(&pfdev->js->job_lock, flags);
-	for (i = 0; i < NUM_JOB_SLOTS; i++) {
-		if (pfdev->jobs[i]) {
-			pm_runtime_put_noidle(pfdev->dev);
-			panfrost_devfreq_record_idle(&pfdev->pfdevfreq);
-			pfdev->jobs[i] = NULL;
-		}
-	}
-	spin_unlock_irqrestore(&pfdev->js->job_lock, flags);
-
-	panfrost_device_reset(pfdev);
-
-	for (i = 0; i < NUM_JOB_SLOTS; i++)
-		drm_sched_resubmit_jobs(&pfdev->js->queue[i].sched);
-
-	mutex_unlock(&pfdev->reset_lock);
-
-	/* restart scheduler after GPU is usable again */
-	for (i = 0; i < NUM_JOB_SLOTS; i++)
-		drm_sched_start(&pfdev->js->queue[i].sched, true);
+	/* Schedule a reset if there's no reset in progress. */
+	if (!atomic_cmpxchg(&pfdev->reset.pending, 0, 1))
+		schedule_work(&pfdev->reset.work);
 }
 
 static const struct drm_sched_backend_ops panfrost_sched_ops = {
@@ -531,11 +504,59 @@  static irqreturn_t panfrost_job_irq_handler(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+static void panfrost_reset(struct work_struct *work)
+{
+	struct panfrost_device *pfdev = container_of(work,
+						     struct panfrost_device,
+						     reset.work);
+	unsigned long flags;
+	unsigned int i;
+
+	for (i = 0; i < NUM_JOB_SLOTS; i++) {
+		/*
+		 * We want pending timeouts to be handled before we attempt
+		 * to stop the scheduler. If we don't do that and the timeout
+		 * handler is in flight, it might have removed the bad job
+		 * from the list, and we'll lose this job if the reset handler
+		 * enters the critical section in panfrost_scheduler_stop()
+		 * before the timeout handler.
+		 *
+		 * Timeout is set to max to make sure the timer is not
+		 * restarted after the cancellation.
+		 */
+		pfdev->js->queue[i].sched.timeout = MAX_SCHEDULE_TIMEOUT;
+		cancel_delayed_work_sync(&pfdev->js->queue[i].sched.work_tdr);
+		panfrost_scheduler_stop(&pfdev->js->queue[i], NULL);
+	}
+
+	/* All timers have been stopped, we can safely reset the pending state. */
+	atomic_set(&pfdev->reset.pending, 0);
+
+	spin_lock_irqsave(&pfdev->js->job_lock, flags);
+	for (i = 0; i < NUM_JOB_SLOTS; i++) {
+		if (pfdev->jobs[i]) {
+			pm_runtime_put_noidle(pfdev->dev);
+			panfrost_devfreq_record_idle(&pfdev->pfdevfreq);
+			pfdev->jobs[i] = NULL;
+		}
+	}
+	spin_unlock_irqrestore(&pfdev->js->job_lock, flags);
+
+	panfrost_device_reset(pfdev);
+
+	for (i = 0; i < NUM_JOB_SLOTS; i++) {
+		drm_sched_resubmit_jobs(&pfdev->js->queue[i].sched);
+		panfrost_scheduler_start(&pfdev->js->queue[i]);
+	}
+}
+
 int panfrost_job_init(struct panfrost_device *pfdev)
 {
 	struct panfrost_job_slot *js;
 	int ret, j, irq;
 
+	INIT_WORK(&pfdev->reset.work, panfrost_reset);
+
 	pfdev->js = js = devm_kzalloc(pfdev->dev, sizeof(*js), GFP_KERNEL);
 	if (!js)
 		return -ENOMEM;
@@ -560,7 +581,7 @@  int panfrost_job_init(struct panfrost_device *pfdev)
 
 		ret = drm_sched_init(&js->queue[j].sched,
 				     &panfrost_sched_ops,
-				     1, 0, msecs_to_jiffies(500),
+				     1, 0, msecs_to_jiffies(JOB_TIMEOUT_MS),
 				     "pan_js");
 		if (ret) {
 			dev_err(pfdev->dev, "Failed to create scheduler: %d.", ret);