[PATCH v6 09/16] drm/panfrost: Simplify the reset serialization logic
Boris Brezillon
boris.brezillon at collabora.com
Wed Jun 30 06:27:44 UTC 2021
Now that we can pass our own workqueue to drm_sched_init(), we can use
an ordered workqueue on for both the scheduler timeout tdr and our own
reset work (which we use when the reset is not caused by a fault/timeout
on a specific job, like when we have AS_ACTIVE bit stuck). This
guarantees that the timeout handlers and reset handler can't run
concurrently which drastically simplifies the locking.
v5:
* Don't call cancel_delayed_timeout() in the reset path (those works
are canceled in drm_sched_stop())
v4:
* Actually pass the reset workqueue to drm_sched_init()
* Don't call cancel_work_sync() in panfrost_reset(). It will deadlock
since it might be called from the reset work, which is executing and
cancel_work_sync() will wait for the handler to return. Checking the
reset pending status should avoid spurious resets
v3:
* New patch
Suggested-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
Reviewed-by: Steven Price <steven.price at arm.com>
---
drivers/gpu/drm/panfrost/panfrost_device.h | 6 +-
drivers/gpu/drm/panfrost/panfrost_job.c | 186 ++++++++-------------
2 files changed, 69 insertions(+), 123 deletions(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
index aec11b6f5abc..d37bc09809e8 100644
--- a/drivers/gpu/drm/panfrost/panfrost_device.h
+++ b/drivers/gpu/drm/panfrost/panfrost_device.h
@@ -109,6 +109,7 @@ struct panfrost_device {
struct mutex sched_lock;
struct {
+ struct workqueue_struct *wq;
struct work_struct work;
atomic_t pending;
} reset;
@@ -247,9 +248,8 @@ const char *panfrost_exception_name(u32 exception_code);
static inline void
panfrost_device_schedule_reset(struct panfrost_device *pfdev)
{
- /* Schedule a reset if there's no reset in progress. */
- if (!atomic_xchg(&pfdev->reset.pending, 1))
- schedule_work(&pfdev->reset.work);
+ atomic_set(&pfdev->reset.pending, 1);
+ queue_work(pfdev->reset.wq, &pfdev->reset.work);
}
#endif
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index 6149e4c7133f..59c23c91e47c 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -25,17 +25,8 @@
#define job_write(dev, reg, data) writel(data, dev->iomem + (reg))
#define job_read(dev, reg) readl(dev->iomem + (reg))
-enum panfrost_queue_status {
- PANFROST_QUEUE_STATUS_ACTIVE,
- PANFROST_QUEUE_STATUS_STOPPED,
- PANFROST_QUEUE_STATUS_STARTING,
- PANFROST_QUEUE_STATUS_FAULT_PENDING,
-};
-
struct panfrost_queue_state {
struct drm_gpu_scheduler sched;
- atomic_t status;
- struct mutex lock;
u64 fence_context;
u64 emit_seqno;
};
@@ -368,57 +359,67 @@ void panfrost_job_enable_interrupts(struct panfrost_device *pfdev)
job_write(pfdev, JOB_INT_MASK, irq_mask);
}
-static bool panfrost_scheduler_stop(struct panfrost_queue_state *queue,
- struct drm_sched_job *bad)
+static void panfrost_reset(struct panfrost_device *pfdev,
+ struct drm_sched_job *bad)
{
- enum panfrost_queue_status old_status;
- bool stopped = false;
+ unsigned int i;
+ bool cookie;
- mutex_lock(&queue->lock);
- old_status = atomic_xchg(&queue->status,
- PANFROST_QUEUE_STATUS_STOPPED);
- if (old_status == PANFROST_QUEUE_STATUS_STOPPED)
- goto out;
+ if (!atomic_read(&pfdev->reset.pending))
+ return;
+
+ /* Stop the schedulers.
+ *
+ * FIXME: We temporarily get out of the dma_fence_signalling section
+ * because the cleanup path generate lockdep splats when taking locks
+ * to release job resources. We should rework the code to follow this
+ * pattern:
+ *
+ * try_lock
+ * if (locked)
+ * release
+ * else
+ * schedule_work_to_release_later
+ */
+ for (i = 0; i < NUM_JOB_SLOTS; i++)
+ drm_sched_stop(&pfdev->js->queue[i].sched, bad);
+
+ cookie = dma_fence_begin_signalling();
- WARN_ON(old_status != PANFROST_QUEUE_STATUS_ACTIVE);
- drm_sched_stop(&queue->sched, bad);
if (bad)
drm_sched_increase_karma(bad);
- stopped = true;
+ spin_lock(&pfdev->js->job_lock);
+ 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(&pfdev->js->job_lock);
- /*
- * Set the timeout to max so the timer doesn't get started
- * when we return from the timeout handler (restored in
- * panfrost_scheduler_start()).
+ panfrost_device_reset(pfdev);
+
+ /* GPU has been reset, we can clear the reset pending bit. */
+ atomic_set(&pfdev->reset.pending, 0);
+
+ /* Now resubmit jobs that were previously queued but didn't have a
+ * chance to finish.
+ * FIXME: We temporarily get out of the DMA fence signalling section
+ * while resubmitting jobs because the job submission logic will
+ * allocate memory with the GFP_KERNEL flag which can trigger memory
+ * reclaim and exposes a lock ordering issue.
*/
- queue->sched.timeout = MAX_SCHEDULE_TIMEOUT;
+ dma_fence_end_signalling(cookie);
+ for (i = 0; i < NUM_JOB_SLOTS; i++)
+ drm_sched_resubmit_jobs(&pfdev->js->queue[i].sched);
+ cookie = dma_fence_begin_signalling();
-out:
- mutex_unlock(&queue->lock);
+ for (i = 0; i < NUM_JOB_SLOTS; i++)
+ drm_sched_start(&pfdev->js->queue[i].sched, true);
- return stopped;
-}
-
-static void panfrost_scheduler_start(struct panfrost_queue_state *queue)
-{
- enum panfrost_queue_status old_status;
-
- mutex_lock(&queue->lock);
- old_status = atomic_xchg(&queue->status,
- PANFROST_QUEUE_STATUS_STARTING);
- WARN_ON(old_status != PANFROST_QUEUE_STATUS_STOPPED);
-
- /* Restore the original timeout before starting the scheduler. */
- queue->sched.timeout = msecs_to_jiffies(JOB_TIMEOUT_MS);
- drm_sched_resubmit_jobs(&queue->sched);
- drm_sched_start(&queue->sched, true);
- old_status = atomic_xchg(&queue->status,
- PANFROST_QUEUE_STATUS_ACTIVE);
- if (old_status == PANFROST_QUEUE_STATUS_FAULT_PENDING)
- drm_sched_fault(&queue->sched);
-
- mutex_unlock(&queue->lock);
+ dma_fence_end_signalling(cookie);
}
static enum drm_gpu_sched_stat panfrost_job_timedout(struct drm_sched_job
@@ -443,11 +444,8 @@ static enum drm_gpu_sched_stat panfrost_job_timedout(struct drm_sched_job
job_read(pfdev, JS_TAIL_LO(js)),
sched_job);
- /* Scheduler is already stopped, nothing to do. */
- if (!panfrost_scheduler_stop(&pfdev->js->queue[js], sched_job))
- return DRM_GPU_SCHED_STAT_NOMINAL;
-
- panfrost_device_schedule_reset(pfdev);
+ atomic_set(&pfdev->reset.pending, 1);
+ panfrost_reset(pfdev, sched_job);
return DRM_GPU_SCHED_STAT_NOMINAL;
}
@@ -474,8 +472,6 @@ static void panfrost_job_handle_irq(struct panfrost_device *pfdev, u32 status)
job_write(pfdev, JOB_INT_CLEAR, mask);
if (status & JOB_INT_MASK_ERR(j)) {
- enum panfrost_queue_status old_status;
-
job_write(pfdev, JS_COMMAND_NEXT(j), JS_COMMAND_NOP);
dev_err(pfdev->dev, "js fault, js=%d, status=%s, head=0x%x, tail=0x%x",
@@ -483,19 +479,7 @@ static void panfrost_job_handle_irq(struct panfrost_device *pfdev, u32 status)
panfrost_exception_name(job_read(pfdev, JS_STATUS(j))),
job_read(pfdev, JS_HEAD_LO(j)),
job_read(pfdev, JS_TAIL_LO(j)));
-
- /*
- * When the queue is being restarted we don't report
- * faults directly to avoid races between the timeout
- * and reset handlers. panfrost_scheduler_start() will
- * call drm_sched_fault() after the queue has been
- * started if status == FAULT_PENDING.
- */
- old_status = atomic_cmpxchg(&pfdev->js->queue[j].status,
- PANFROST_QUEUE_STATUS_STARTING,
- PANFROST_QUEUE_STATUS_FAULT_PENDING);
- if (old_status == PANFROST_QUEUE_STATUS_ACTIVE)
- drm_sched_fault(&pfdev->js->queue[j].sched);
+ drm_sched_fault(&pfdev->js->queue[j].sched);
}
if (status & JOB_INT_MASK_DONE(j)) {
@@ -550,56 +534,13 @@ static irqreturn_t panfrost_job_irq_handler(int irq, void *data)
return IRQ_WAKE_THREAD;
}
-static void panfrost_reset(struct work_struct *work)
+static void panfrost_reset_work(struct work_struct *work)
{
struct panfrost_device *pfdev = container_of(work,
struct panfrost_device,
reset.work);
- unsigned int i;
- bool cookie;
- cookie = dma_fence_begin_signalling();
- 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_SCHEDULE_TIMEOUT - 1 because we need
- * something big enough to make sure the timer will not expire
- * before we manage to stop the scheduler, but we can't use
- * MAX_SCHEDULE_TIMEOUT because drm_sched_get_cleanup_job()
- * considers that as 'timer is not running' and will dequeue
- * the job without making sure the timeout handler is not
- * running.
- */
- pfdev->js->queue[i].sched.timeout = MAX_SCHEDULE_TIMEOUT - 1;
- 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(&pfdev->js->job_lock);
- 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(&pfdev->js->job_lock);
-
- panfrost_device_reset(pfdev);
-
- for (i = 0; i < NUM_JOB_SLOTS; i++)
- panfrost_scheduler_start(&pfdev->js->queue[i]);
-
- dma_fence_end_signalling(cookie);
+ panfrost_reset(pfdev, NULL);
}
int panfrost_job_init(struct panfrost_device *pfdev)
@@ -607,7 +548,7 @@ int panfrost_job_init(struct panfrost_device *pfdev)
struct panfrost_job_slot *js;
int ret, j, irq;
- INIT_WORK(&pfdev->reset.work, panfrost_reset);
+ INIT_WORK(&pfdev->reset.work, panfrost_reset_work);
pfdev->js = js = devm_kzalloc(pfdev->dev, sizeof(*js), GFP_KERNEL);
if (!js)
@@ -629,15 +570,18 @@ int panfrost_job_init(struct panfrost_device *pfdev)
return ret;
}
- for (j = 0; j < NUM_JOB_SLOTS; j++) {
- mutex_init(&js->queue[j].lock);
+ pfdev->reset.wq = alloc_ordered_workqueue("panfrost-reset", 0);
+ if (!pfdev->reset.wq)
+ return -ENOMEM;
+ for (j = 0; j < NUM_JOB_SLOTS; j++) {
js->queue[j].fence_context = dma_fence_context_alloc(1);
ret = drm_sched_init(&js->queue[j].sched,
&panfrost_sched_ops,
1, 0,
- msecs_to_jiffies(JOB_TIMEOUT_MS), NULL,
+ msecs_to_jiffies(JOB_TIMEOUT_MS),
+ pfdev->reset.wq,
NULL, "pan_js");
if (ret) {
dev_err(pfdev->dev, "Failed to create scheduler: %d.", ret);
@@ -653,6 +597,7 @@ int panfrost_job_init(struct panfrost_device *pfdev)
for (j--; j >= 0; j--)
drm_sched_fini(&js->queue[j].sched);
+ destroy_workqueue(pfdev->reset.wq);
return ret;
}
@@ -665,9 +610,10 @@ void panfrost_job_fini(struct panfrost_device *pfdev)
for (j = 0; j < NUM_JOB_SLOTS; j++) {
drm_sched_fini(&js->queue[j].sched);
- mutex_destroy(&js->queue[j].lock);
}
+ cancel_work_sync(&pfdev->reset.work);
+ destroy_workqueue(pfdev->reset.wq);
}
int panfrost_job_open(struct panfrost_file_priv *panfrost_priv)
--
2.31.1
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