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

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commit 5bc5cc2819c2c0adb644919e3e790b504ea47e0a upstream.

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>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201105151704.2010667-1-boris.brezillon@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Boris Brezillon 2020-11-05 16:17:04 +01:00 committed by Greg Kroah-Hartman
parent a61da034c5
commit 86fcb7910d
3 changed files with 130 additions and 64 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/gpu/drm/panfrost/panfrost_device.c
View File

@ -206,7 +206,6 @@ 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);

6
drivers/gpu/drm/panfrost/panfrost_device.h
View File

@ -105,7 +105,11 @@ 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;

187
drivers/gpu/drm/panfrost/panfrost_job.c
View File

@ -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;
@ -558,7 +621,7 @@ 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);