BUG/MEDIUM: threads: fix double-word CAS on non-optimized 32-bit platforms
On armv7 haproxy doesn't work because of the fixes on the double-word
CAS. There are two issues. The first one is that the last argument in
case of dwcas is a pointer to the set of value and not a value ; the
second is that it's not enough to cast the data as (void*) since it will
be a single word. Let's fix this by using the pointers as an array of
long. This was tested on i386, armv7, x86_64 and aarch64 and it is now
fine. An alternate approach using a struct was attempted as well but it
used to produce less optimal code.
This fix must be backported to 1.9. This fixes github issue #105.
Cc: Olivier Houchard <ohouchard@haproxy.com>
diff --git a/include/common/hathreads.h b/include/common/hathreads.h
index 268dd63..0ba56d0 100644
--- a/include/common/hathreads.h
+++ b/include/common/hathreads.h
@@ -77,7 +77,19 @@
#define __decl_aligned_rwlock(lock)
#define HA_ATOMIC_CAS(val, old, new) ({((*val) == (*old)) ? (*(val) = (new) , 1) : (*(old) = *(val), 0);})
-#define HA_ATOMIC_DWCAS(val, o, n) ({((*val) == (*o)) ? (*(val) = (n) , 1) : (*(o) = *(val), 0);})
+
+/* warning, n is a pointer to the double value for dwcas */
+#define HA_ATOMIC_DWCAS(val, o, n) \
+ ({ \
+ long *_v = (long*)(val); \
+ long *_o = (long*)(o); \
+ long *_n = (long*)(n); \
+ long _v0 = _v[0], _v1 = _v[1]; \
+ (_v0 == _o[0] && _v1 == _o[1]) ? \
+ (_v[0] = _n[0], _v[1] = _n[1], 1) : \
+ (_o[0] = _v0, _o[1] = _v1, 0); \
+ })
+
#define HA_ATOMIC_ADD(val, i) ({*(val) += (i);})
#define HA_ATOMIC_SUB(val, i) ({*(val) -= (i);})
#define HA_ATOMIC_XADD(val, i) \
@@ -293,6 +305,7 @@
__ret_cas; \
})
+/* warning, n is a pointer to the double value for dwcas */
#define HA_ATOMIC_DWCAS(val, o, n) __ha_cas_dw(val, o, n)
#define HA_ATOMIC_XCHG(val, new) \
@@ -337,6 +350,7 @@
#else
/* gcc >= 4.7 */
#define HA_ATOMIC_CAS(val, old, new) __atomic_compare_exchange_n(val, old, new, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
+/* warning, n is a pointer to the double value for dwcas */
#define HA_ATOMIC_DWCAS(val, o, n) __ha_cas_dw(val, o, n)
#define HA_ATOMIC_ADD(val, i) __atomic_add_fetch(val, i, __ATOMIC_SEQ_CST)
#define HA_ATOMIC_XADD(val, i) __atomic_fetch_add(val, i, __ATOMIC_SEQ_CST)
@@ -366,6 +380,7 @@
* ie updating a counter. Otherwise a barrier is required.
*/
#define _HA_ATOMIC_CAS(val, old, new) __atomic_compare_exchange_n(val, old, new, 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED)
+/* warning, n is a pointer to the double value for dwcas */
#define _HA_ATOMIC_DWCAS(val, o, n) __ha_cas_dw(val, o, n)
#define _HA_ATOMIC_ADD(val, i) __atomic_add_fetch(val, i, __ATOMIC_RELAXED)
#define _HA_ATOMIC_XADD(val, i) __atomic_fetch_add(val, i, __ATOMIC_RELAXED)