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Commit 556b7487 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Give each sw_fence its own lockclass 



Localise the static struct lock_class_key to the caller of
i915_sw_fence_init() so that we create a lock_class instance for each
unique sw_fence rather than all sw_fences sharing the same
lock_class. This eliminate some lockdep false positive when using fences
from within fence callbacks.

For the relatively small number of fences currently in use [2], this adds
160 bytes of unused text/code when lockdep is disabled. This seems
quite high, but fully reducing it via ifdeffery is also quite ugly.
Removing the #fence strings saves 72 bytes with just a single #ifdef.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161114204105.29171-1-chris@chris-wilson.co.uk
parent e3c566df

drivers/gpu/drm/i915/i915_sw_fence.c

+5 −2
Original line number Diff line number Diff line
@@ -116,11 +116,14 @@ static void i915_sw_fence_await(struct i915_sw_fence *fence) 
	WARN_ON(atomic_inc_return(&fence->pending) <= 1);

}



void i915_sw_fence_init(struct i915_sw_fence *fence, i915_sw_fence_notify_t fn)

void __i915_sw_fence_init(struct i915_sw_fence *fence,

			  i915_sw_fence_notify_t fn,

			  const char *name,

			  struct lock_class_key *key)

{

	BUG_ON((unsigned long)fn & ~I915_SW_FENCE_MASK);



	init_waitqueue_head(&fence->wait);

	__init_waitqueue_head(&fence->wait, name, key);

	kref_init(&fence->kref);

	atomic_set(&fence->pending, 1);

	fence->flags = (unsigned long)fn;

drivers/gpu/drm/i915/i915_sw_fence.h

+16 −1
Original line number Diff line number Diff line
@@ -40,7 +40,22 @@ typedef int (*i915_sw_fence_notify_t)(struct i915_sw_fence *, 
				      enum i915_sw_fence_notify state);

#define __i915_sw_fence_call __aligned(4)



void i915_sw_fence_init(struct i915_sw_fence *fence, i915_sw_fence_notify_t fn);

void __i915_sw_fence_init(struct i915_sw_fence *fence,

			  i915_sw_fence_notify_t fn,

			  const char *name,

			  struct lock_class_key *key);

#ifdef CONFIG_LOCKDEP

#define i915_sw_fence_init(fence, fn)				\

do {								\

	static struct lock_class_key __key;			\

								\

	__i915_sw_fence_init((fence), (fn), #fence, &__key);	\

} while (0)

#else

#define i915_sw_fence_init(fence, fn)				\

	__i915_sw_fence_init((fence), (fn), NULL, NULL)

#endif



void i915_sw_fence_commit(struct i915_sw_fence *fence);



int i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,