From 78ef2d9abad6da3f94489148b4e08359dd2fb4fe Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 15 Aug 2016 10:48:49 +0100 Subject: [PATCH] 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 Cc: Joonas Lahtinen Cc: Daniel Vetter Reviewed-by: Joonas Lahtinen 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 | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 25b1e6c010d5..855833a6306a 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -3920,4 +3920,10 @@ bool i915_memcpy_from_wc(void *dst, const void *src, unsigned long len); #define ptr_pack_bits(ptr, bits) \ ((typeof(ptr))((unsigned long)(ptr) | (bits))) +#define fetch_and_zero(ptr) ({ \ + typeof(*ptr) __T = *(ptr); \ + *(ptr) = (typeof(*ptr))0; \ + __T; \ +}) + #endif -- 2.39.5