drm/i915: Mark intel_wakeref_get() as a sleeper

Assume that intel_wakeref_get() may take the mutex, and perform other
sleeping actions in the course of its callbacks and so use might_sleep()
to ensure that all callers abide. Anything that cannot sleep has to use
e.g. intel_wakeref_get_if_active() to guarantee its avoidance of the
non-atomic paths.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191121130528.309474-1-chris@chris-wilson.co.uk

1 files changed, 17 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_wakeref.h b/drivers/gpu/drm/i915/intel_wakeref.h
index da6e8fd506e6..8d945db94b7a 100644
--- a/drivers/gpu/drm/i915/intel_wakeref.h
+++ b/drivers/gpu/drm/i915/intel_wakeref.h
@@ -59,9 +59,7 @@ void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags);
 
 /**
  * intel_wakeref_get: Acquire the wakeref
- * @i915: the drm_i915_private device
  * @wf: the wakeref
- * @fn: callback for acquired the wakeref, called only on first acquire.
  *
  * Acquire a hold on the wakeref. The first user to do so, will acquire
  * the runtime pm wakeref and then call the @fn underneath the wakeref
@@ -76,6 +74,7 @@ void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags);
 static inline int
 intel_wakeref_get(struct intel_wakeref *wf)
 {
+	might_sleep();
 	if (unlikely(!atomic_inc_not_zero(&wf->count)))
 		return __intel_wakeref_get_first(wf);
 
@@ -83,6 +82,22 @@ intel_wakeref_get(struct intel_wakeref *wf)
 }
 
 /**
+ * __intel_wakeref_get: Acquire the wakeref, again
+ * @wf: the wakeref
+ *
+ * Increment the wakeref counter, only valid if it is already held by
+ * the caller.
+ *
+ * See intel_wakeref_get().
+ */
+static inline void
+__intel_wakeref_get(struct intel_wakeref *wf)
+{
+	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
+	atomic_inc(&wf->count);
+}
+
+/**
  * intel_wakeref_get_if_in_use: Acquire the wakeref
  * @wf: the wakeref
  *