Trying to do a modeset from within a reset is fraught with danger. We
can fall into a cyclic deadlock where the modeset is waiting on a
previous modeset that is waiting on a request, and since the GPU hung
that request completion is waiting on the reset. As modesetting doesn't
allow its locks to be broken and restarted, or for its *own* reset
mechanism to take over the display, we have to do something very
evil instead. If we detect that we are stuck waiting to prepare the
display reset (by using a very simple timeout), resort to cancelling all
in-flight requests and throwing the user data into /dev/null, which is
marginally better than the driver locking up and keeping that data to
itself.
This is not a fix; this is just a workaround that unbreaks machines
until we can resolve the deadlock in a way that doesn't lose data!
v2: Move the retirement from set-wegded to the i915_reset() error path,
after which we no longer any delayed worker cleanup for
i915_handle_error()
v3: C abuse for syntactic sugar
v4: Cover all waits with the timeout to catch more driver breakage
References: https://bugs.freedesktop.org/show_bug.cgi?id=99093
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.c | 1 +
drivers/gpu/drm/i915/i915_gem.c | 18 +++-------
drivers/gpu/drm/i915/i915_irq.c | 79 ++++++++++++++++++++++++++++++-----------
3 files changed, 64 insertions(+), 34 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index d1aa10c9cc5d..1df957b986c7 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1914,6 +1914,7 @@ void i915_reset(struct drm_i915_private *dev_priv)
error:
i915_gem_set_wedged(dev_priv);
+ i915_gem_retire_requests(dev_priv);
goto finish;
}
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7391e2d36a31..8bc9a3f53006 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3046,7 +3046,8 @@ static void engine_set_wedged(struct intel_engine_cs *engine)
/* Mark all executing requests as skipped */
spin_lock_irqsave(&engine->timeline->lock, flags);
list_for_each_entry(request, &engine->timeline->requests, link)
- dma_fence_set_error(&request->fence, -EIO);
+ if (!i915_gem_request_completed(request))
+ dma_fence_set_error(&request->fence, -EIO);
spin_unlock_irqrestore(&engine->timeline->lock, flags);
/* Mark all pending requests as complete so that any concurrent
@@ -3092,6 +3093,7 @@ static int __i915_gem_set_wedged_BKL(void *data)
struct intel_engine_cs *engine;
enum intel_engine_id id;
+ set_bit(I915_WEDGED, &i915->gpu_error.flags);
for_each_engine(engine, i915, id)
engine_set_wedged(engine);
@@ -3100,20 +3102,7 @@ static int __i915_gem_set_wedged_BKL(void *data)
void i915_gem_set_wedged(struct drm_i915_private *dev_priv)
{
- lockdep_assert_held(&dev_priv->drm.struct_mutex);
- set_bit(I915_WEDGED, &dev_priv->gpu_error.flags);
-
- /* Retire completed requests first so the list of inflight/incomplete
- * requests is accurate and we don't try and mark successful requests
- * as in error during __i915_gem_set_wedged_BKL().
- */
- i915_gem_retire_requests(dev_priv);
-
stop_machine(__i915_gem_set_wedged_BKL, dev_priv, NULL);
-
- i915_gem_contexts_lost(dev_priv);
-
- mod_delayed_work(dev_priv->wq, &dev_priv->gt.idle_work, 0);
}
bool i915_gem_unset_wedged(struct drm_i915_private *i915)
@@ -3168,6 +3157,7 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
* context and do not require stop_machine().
*/
intel_engines_reset_default_submission(i915);
+ i915_gem_contexts_lost(i915);
smp_mb__before_atomic(); /* complete takeover before enabling execbuf */
clear_bit(I915_WEDGED, &i915->gpu_error.flags);
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 61047ee2eede..5fa2a1cf71b8 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2587,6 +2587,46 @@ static irqreturn_t gen8_irq_handler(int irq, void *arg)
return ret;
}
+struct wedge_me {
+ struct delayed_work work;
+ struct drm_i915_private *i915;
+ const char *name;
+};
+
+static void wedge_me(struct work_struct *work)
+{
+ struct wedge_me *w = container_of(work, typeof(*w), work.work);
+
+ dev_err(w->i915->drm.dev,
+ "%s timed out, cancelling all in-flight rendering.\n",
+ w->name);
+ i915_gem_set_wedged(w->i915);
+}
+
+static void __init_wedge(struct wedge_me *w,
+ struct drm_i915_private *i915,
+ long timeout,
+ const char *name)
+{
+ w->i915 = i915;
+ w->name = name;
+
+ INIT_DELAYED_WORK_ONSTACK(&w->work, wedge_me);
+ schedule_delayed_work(&w->work, timeout);
+}
+
+static void __fini_wedge(struct wedge_me *w)
+{
+ cancel_delayed_work_sync(&w->work);
+ destroy_delayed_work_on_stack(&w->work);
+ w->i915 = NULL;
+}
+
+#define i915_wedge_on_timeout(W, DEV, TIMEOUT) \
+ for (__init_wedge((W), (DEV), (TIMEOUT), __func__); \
+ (W)->i915; \
+ __fini_wedge((W)))
+
/**
* i915_reset_device - do process context error handling work
* @dev_priv: i915 device private
@@ -2600,36 +2640,35 @@ static void i915_reset_device(struct drm_i915_private *dev_priv)
char *error_event[] = { I915_ERROR_UEVENT "=1", NULL };
char *reset_event[] = { I915_RESET_UEVENT "=1", NULL };
char *reset_done_event[] = { I915_ERROR_UEVENT "=0", NULL };
+ struct wedge_me w;
kobject_uevent_env(kobj, KOBJ_CHANGE, error_event);
DRM_DEBUG_DRIVER("resetting chip\n");
kobject_uevent_env(kobj, KOBJ_CHANGE, reset_event);
- intel_prepare_reset(dev_priv);
+ i915_wedge_on_timeout(&w, dev_priv, 5*HZ) {
+ intel_prepare_reset(dev_priv);
- set_bit(I915_RESET_HANDOFF, &dev_priv->gpu_error.flags);
- wake_up_all(&dev_priv->gpu_error.wait_queue);
+ /* Signal that locked waiters should reset the GPU */
+ set_bit(I915_RESET_HANDOFF, &dev_priv->gpu_error.flags);
+ wake_up_all(&dev_priv->gpu_error.wait_queue);
- do {
- /*
- * All state reset _must_ be completed before we update the
- * reset counter, for otherwise waiters might miss the reset
- * pending state and not properly drop locks, resulting in
- * deadlocks with the reset work.
+ /* Wait for anyone holding the lock to wakeup, without
+ * blocking indefinitely on struct_mutex.
*/
- if (mutex_trylock(&dev_priv->drm.struct_mutex)) {
- i915_reset(dev_priv);
- mutex_unlock(&dev_priv->drm.struct_mutex);
- }
-
- /* We need to wait for anyone holding the lock to wakeup */
- } while (wait_on_bit_timeout(&dev_priv->gpu_error.flags,
- I915_RESET_HANDOFF,
- TASK_UNINTERRUPTIBLE,
- HZ));
+ do {
+ if (mutex_trylock(&dev_priv->drm.struct_mutex)) {
+ i915_reset(dev_priv);
+ mutex_unlock(&dev_priv->drm.struct_mutex);
+ }
+ } while (wait_on_bit_timeout(&dev_priv->gpu_error.flags,
+ I915_RESET_HANDOFF,
+ TASK_UNINTERRUPTIBLE,
+ 1));
- intel_finish_reset(dev_priv);
+ intel_finish_reset(dev_priv);
+ }
if (!test_bit(I915_WEDGED, &dev_priv->gpu_error.flags))
kobject_uevent_env(kobj,
