Fix bugs in my_atomic_cas*(val,cmp,new) that *cmp is accessed after CAS succeds.

In the gcc builtin implementation, problem was that *cmp was read
again after atomic CAS to check if old *val == *cmp; this fails if CAS
is successfull and another thread modifies *cmp in-between.

In the x86-gcc implementation, problem was that *cmp was set also in
the case of successful CAS; this means there is a window where it can
clobber a value written by another thread after successful CAS.

---
 include/atomic/gcc_builtins.h |    5 +++--
 include/atomic/x86-gcc.h      |    6 +++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

Index: work-5.1-groupcommit/include/atomic/gcc_builtins.h
===================================================================
--- work-5.1-groupcommit.orig/include/atomic/gcc_builtins.h	2010-06-09 11:53:59.000000000 +0200
+++ work-5.1-groupcommit/include/atomic/gcc_builtins.h	2010-06-09 11:54:06.000000000 +0200
@@ -19,8 +19,9 @@
   v= __sync_lock_test_and_set(a, v);
 #define make_atomic_cas_body(S)                     \
   int ## S sav;                                     \
-  sav= __sync_val_compare_and_swap(a, *cmp, set);   \
-  if (!(ret= (sav == *cmp))) *cmp= sav;
+  int ## S cmp_val= *cmp;                           \
+  sav= __sync_val_compare_and_swap(a, cmp_val, set);\
+  if (!(ret= (sav == cmp_val))) *cmp= sav
 
 #ifdef MY_ATOMIC_MODE_DUMMY
 #define make_atomic_load_body(S)   ret= *a
Index: work-5.1-groupcommit/include/atomic/x86-gcc.h
===================================================================
--- work-5.1-groupcommit.orig/include/atomic/x86-gcc.h	2010-06-09 11:53:59.000000000 +0200
+++ work-5.1-groupcommit/include/atomic/x86-gcc.h	2010-06-09 11:54:06.000000000 +0200
@@ -45,8 +45,12 @@
 #define make_atomic_fas_body(S)				\
   asm volatile ("xchg %0, %1;" : "+r" (v) , "+m" (*a))
 #define make_atomic_cas_body(S)					\
+  int ## S sav;                                     \
   asm volatile (LOCK_prefix "; cmpxchg %3, %0; setz %2;"	\
-               : "+m" (*a), "+a" (*cmp), "=q" (ret): "r" (set))
+               : "+m" (*a), "=a" (sav), "=q" (ret)              \
+               : "r" (set), "a" (*cmp));                        \
+  if (!ret)                                                     \
+    *cmp= sav
 
 #ifdef MY_ATOMIC_MODE_DUMMY
 #define make_atomic_load_body(S)   ret=*a