drm/i915: Add fetch_and_zero() macro
authorChris Wilson <chris@chris-wilson.co.uk>
Mon, 15 Aug 2016 09:48:49 +0000 (10:48 +0100)
committerChris Wilson <chris@chris-wilson.co.uk>
Mon, 15 Aug 2016 10:00:56 +0000 (11:00 +0100)
commit78ef2d9abad6da3f94489148b4e08359dd2fb4fe
tree971f32e48f9b5773d5a2b1735650401de08c1f8a
parent81a8aa4a6c8535955c8b795c762489d0edf9a648
drm/i915: Add fetch_and_zero() macro

A simple little macro to clear a pointer and return the old value. This
is useful for writing

value = *ptr;
if (!value)
return;

*ptr = 0;
...
free(value);

in a slightly more concise form:

value = fetch_and_zero(ptr);
if (!value)
return;

...
free(value);

with the idea that this establishes a pattern that may be extended for
atomic use (using xchg or cmpxchg) i.e. atomic_fetch_and_zero() and
similar to llist.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471254551-25805-10-git-send-email-chris@chris-wilson.co.uk
drivers/gpu/drm/i915/i915_drv.h