From: José Fonseca <jfonseca@vmware.com>
Date: Tue, 25 Nov 2014 14:25:28 +0000 (+0000)
Subject: util/u_atomic: Fix the unlocked implementation.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=a5299e9e1ca45f7bcf72347dc0fd47986d779769;p=mesa.git

util/u_atomic: Fix the unlocked implementation.

It was totally broken:

- p_atomic_dec_zero() was returning the negation of the expected value

- p_atomic_inc_return()/p_atomic_dec_return() was
  post-incrementing/decrementing, hence returning the old value instead
  of the new

- p_atomic_cmpxchg() was returning the new value on success, instead of
  the old

It is clear this never used in the past. I wonder if it wouldn't be better to
yank it altogether.

Reviewed-by: Matt Turner <mattst88@gmail.com>
---

diff --git a/src/util/u_atomic.h b/src/util/u_atomic.h
index 5867a0f3c99..56c5740bfbd 100644
--- a/src/util/u_atomic.h
+++ b/src/util/u_atomic.h
@@ -57,12 +57,12 @@
 
 #define p_atomic_set(_v, _i) (*(_v) = (_i))
 #define p_atomic_read(_v) (*(_v))
-#define p_atomic_dec_zero(_v) ((bool) --(*(_v)))
-#define p_atomic_inc(_v) ((void) (*(_v))++)
-#define p_atomic_dec(_v) ((void) (*(_v))--)
-#define p_atomic_inc_return(_v) ((*(_v))++)
-#define p_atomic_dec_return(_v) ((*(_v))--)
-#define p_atomic_cmpxchg(_v, old, _new) (*(_v) == old ? *(_v) = (_new) : *(_v))
+#define p_atomic_dec_zero(_v) (p_atomic_dec_return(_v) == 0)
+#define p_atomic_inc(_v) ((void) p_atomic_inc_return(_v))
+#define p_atomic_dec(_v) ((void) p_atomic_dec_return(_v))
+#define p_atomic_inc_return(_v) (++(*(_v)))
+#define p_atomic_dec_return(_v) (--(*(_v)))
+#define p_atomic_cmpxchg(_v, _old, _new) (*(_v) == (_old) ? (*(_v) = (_new), (_old)) : *(_v))
 
 #endif