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