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.

v5: - Simplify panfrost_scheduler_stop() (Steven Price) - Always restart the queue in panfrost_scheduler_start() even if the status is corrupted (Steven Price)

v4: - Rework the logic to prevent a race between drm_sched_start() (reset work) and drm_sched_job_timedout() (timeout work) - Drop Steven's R-b - Add dma_fence annotation to the panfrost_reset() function (Daniel Vetter)

v3: - Replace the atomic_cmpxchg() by an atomic_xchg() (Robin Murphy) - Add Steven's R-b

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

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 | 187 ++++++++++++++------- 3 files changed, 130 insertions(+), 64 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c index 1daf9322954a..fbcf5edbe367 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 e75b7d2192f7..04e6f6f9b742 100644 --- a/drivers/gpu/drm/panfrost/panfrost_job.c +++ b/drivers/gpu/drm/panfrost/panfrost_job.c @@ -20,12 +20,21 @@ #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))

+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; - bool stopped; + atomic_t status; struct mutex lock; u64 fence_context; u64 emit_seqno; @@ -373,28 +382,61 @@ void panfrost_job_enable_interrupts(struct panfrost_device *pfdev) static bool panfrost_scheduler_stop(struct panfrost_queue_state *queue, struct drm_sched_job *bad) { + enum panfrost_queue_status old_status; bool stopped = false;

mutex_lock(&queue->lock); - if (!queue->stopped) { - drm_sched_stop(&queue->sched, bad); - if (bad) - drm_sched_increase_karma(bad); - queue->stopped = true; - stopped = true; - } + old_status = atomic_xchg(&queue->status, + PANFROST_QUEUE_STATUS_STOPPED); + if (old_status == PANFROST_QUEUE_STATUS_STOPPED) + goto out; + + WARN_ON(old_status != PANFROST_QUEUE_STATUS_ACTIVE); + drm_sched_stop(&queue->sched, bad); + if (bad) + drm_sched_increase_karma(bad); + + 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; + +out: mutex_unlock(&queue->lock);

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); +} + 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 +457,9 @@ 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_xchg(&pfdev->reset.pending, 1)) + schedule_work(&pfdev->reset.work); }

static const struct drm_sched_backend_ops panfrost_sched_ops = { @@ -496,6 +491,8 @@ static irqreturn_t panfrost_job_irq_handler(int irq, void *data) 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", @@ -504,7 +501,18 @@ static irqreturn_t panfrost_job_irq_handler(int irq, void *data) job_read(pfdev, JS_HEAD_LO(j)), job_read(pfdev, JS_TAIL_LO(j)));

- drm_sched_fault(&pfdev->js->queue[j].sched); + /* + * 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); }

if (status & JOB_INT_MASK_DONE(j)) { @@ -531,11 +539,66 @@ 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; + 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_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++) + panfrost_scheduler_start(&pfdev->js->queue[i]); + + dma_fence_end_signalling(cookie); +} + 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 +623,7 @@ 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);