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drm/i915: Don't wait for a spinlock inside error capture
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If we can't grab the breadcrumb's spinlock, possibly due to a driver
deadlock inside the waiters, ignore them. Like hangcheck, error
capturing must work no matter how the driver/GPU dies.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20160906073844.22561-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
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Chris Wilson committed Sep 6, 2016
1 parent fc32de9 commit 19eb918
Showing 1 changed file with 20 additions and 5 deletions.
25 changes: 20 additions & 5 deletions drivers/gpu/drm/i915/i915_gpu_error.c
Original file line number Diff line number Diff line change
Expand Up @@ -489,7 +489,10 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
}
}

if (ee->num_waiters) {
if (IS_ERR(ee->waiters)) {
err_printf(m, "%s --- ? waiters [unable to acquire spinlock]\n",
dev_priv->engine[i].name);
} else if (ee->num_waiters) {
err_printf(m, "%s --- %d waiters\n",
dev_priv->engine[i].name,
ee->num_waiters);
Expand Down Expand Up @@ -648,7 +651,8 @@ static void i915_error_state_free(struct kref *error_ref)
i915_error_object_free(ee->wa_ctx);

kfree(ee->requests);
kfree(ee->waiters);
if (!IS_ERR_OR_NULL(ee->waiters))
kfree(ee->waiters);
}

i915_error_object_free(error->semaphore);
Expand Down Expand Up @@ -933,7 +937,14 @@ static void error_record_engine_waiters(struct intel_engine_cs *engine,
ee->num_waiters = 0;
ee->waiters = NULL;

spin_lock(&b->lock);
if (RB_EMPTY_ROOT(&b->waiters))
return;

if (!spin_trylock(&b->lock)) {
ee->waiters = ERR_PTR(-EDEADLK);
return;
}

count = 0;
for (rb = rb_first(&b->waiters); rb != NULL; rb = rb_next(rb))
count++;
Expand All @@ -947,9 +958,13 @@ static void error_record_engine_waiters(struct intel_engine_cs *engine,
if (!waiter)
return;

ee->waiters = waiter;
if (!spin_trylock(&b->lock)) {
kfree(waiter);
ee->waiters = ERR_PTR(-EDEADLK);
return;
}

spin_lock(&b->lock);
ee->waiters = waiter;
for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
struct intel_wait *w = container_of(rb, typeof(*w), node);

Expand Down

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