drm/i915: clear up wedged transitions
We have two important transitions of the wedged state in the current
code:
- 0 -> 1: This means a hang has been detected, and signals to everyone
that they please get of any locks, so that the reset work item can
do its job.
- 1 -> 0: The reset handler has completed.
Now the last transition mixes up two states: "Reset completed and
successful" and "Reset failed". To distinguish these two we do some
tricks with the reset completion, but I simply could not convince
myself that this doesn't race under odd circumstances.
Hence split this up, and add a new terminal state indicating that the
hw is gone for good.
Also add explicit #defines for both states, update comments.
v2: Split out the reset handling bugfix for the throttle ioctl.
v3: s/tmp/wedged/ sugested by Chris Wilson. Also fixup up a rebase
error which prevented this patch from actually compiling.
v4: To unify the wedged state with the reset counter, keep the
reset-in-progress state just as a flag. The terminally-wedged state is
now denoted with a big number.
v5: Add a comment to the reset_counter special values explaining that
WEDGED & RESET_IN_PROGRESS needs to be true for the code to be
correct.
v6: Fixup logic errors introduced with the wedged+reset_counter
unification. Since WEDGED implies reset-in-progress (in a way we're
terminally stuck in the dead-but-reset-not-completed state), we need
ensure that we check for this everywhere. The specific bug was in
wait_for_error, which would simply have timed out.
v7: Extract an inline i915_reset_in_progress helper to make the code
more readable. Also annote the reset-in-progress case with an
unlikely, to help the compiler optimize the fastpath. Do the same for
the terminally wedged case with i915_terminally_wedged.
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 62da6c7..c84743b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -771,11 +771,37 @@
/* Protected by the above dev->gpu_error.lock. */
struct drm_i915_error_state *first_error;
struct work_struct work;
- struct completion completion;
unsigned long last_reset;
- atomic_t wedged;
+ /**
+ * State variable controlling the reset flow
+ *
+ * Upper bits are for the reset counter.
+ *
+ * Lowest bit controls the reset state machine: Set means a reset is in
+ * progress. This state will (presuming we don't have any bugs) decay
+ * into either unset (successful reset) or the special WEDGED value (hw
+ * terminally sour). All waiters on the reset_queue will be woken when
+ * that happens.
+ */
+ atomic_t reset_counter;
+
+ /**
+ * Special values/flags for reset_counter
+ *
+ * Note that the code relies on
+ * I915_WEDGED & I915_RESET_IN_PROGRESS_FLAG
+ * being true.
+ */
+#define I915_RESET_IN_PROGRESS_FLAG 1
+#define I915_WEDGED 0xffffffff
+
+ /**
+ * Waitqueue to signal when the reset has completed. Used by clients
+ * that wait for dev_priv->mm.wedged to settle.
+ */
+ wait_queue_head_t reset_queue;
/* For gpu hang simulation. */
unsigned int stop_rings;
@@ -1543,6 +1569,16 @@
void i915_gem_retire_requests_ring(struct intel_ring_buffer *ring);
int __must_check i915_gem_check_wedge(struct i915_gpu_error *error,
bool interruptible);
+static inline bool i915_reset_in_progress(struct i915_gpu_error *error)
+{
+ return unlikely(atomic_read(&error->reset_counter)
+ & I915_RESET_IN_PROGRESS_FLAG);
+}
+
+static inline bool i915_terminally_wedged(struct i915_gpu_error *error)
+{
+ return atomic_read(&error->reset_counter) == I915_WEDGED;
+}
void i915_gem_reset(struct drm_device *dev);
void i915_gem_clflush_object(struct drm_i915_gem_object *obj);