Hi,
This patch fixes a bug affecting HAProxy compiled with gcc < 4.7 (with
threads). It must be merged in 1.8.
Thanks,
--
Christopher Faulet
>From 12456b597dbfe231ba5ea33457676ea59b505ed5 Mon Sep 17 00:00:00 2001
From: Christopher Faulet <cfau...@haproxy.com>
Date: Fri, 6 Apr 2018 15:33:30 +0200
Subject: [PATCH] BUG/MEDIUM: threads: Fix the max/min calculation because of
name clashes
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
With gcc < 4.7, when HAProxy is built with threads, the macros
HA_ATOMOC_CAS/XCHG/STORE relies on the legacy â__syncâ builtins. These macros
are slightly complicated than the versions relying on the '_atomic'
builtins. Internally, some local variables are defined, prefixed with '__' to
avoid name clashes with the caller.
On the other hand, the macros HA_ATOMIC_UPDATE_MIN/MAX call HA_ATOMIC_CAS. Some
local variables are also definied in these macros, following the same naming
rule as below. The problem is that '__new' variable is used in
HA_ATOMIC_MIN/_MAX and in HA_ATOMIC_CAS. Obviously, the behaviour is undefined
because '__new' in HA_ATOMIC_CAS is left uninitialized. Unfortunatly gcc fails
to detect this error.
To fix the problem, all internal variables to macros are now suffixed with name
of the macros to avoid clashes (for instance, '__new_cas' in HA_ATOMIC_CAS).
This patch must be backported in 1.8.
---
include/common/hathreads.h | 92 +++++++++++++++++++++++-----------------------
1 file changed, 47 insertions(+), 45 deletions(-)
diff --git a/include/common/hathreads.h b/include/common/hathreads.h
index e8b754cf..b0e4b23e 100644
--- a/include/common/hathreads.h
+++ b/include/common/hathreads.h
@@ -41,26 +41,26 @@ extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the threa
#define HA_ATOMIC_OR(val, flags) ({*(val) |= (flags);})
#define HA_ATOMIC_XCHG(val, new) \
({ \
- typeof(*(val)) __old = *(val); \
+ typeof(*(val)) __old_xchg = *(val); \
*(val) = new; \
- __old; \
+ __old_xchg; \
})
#define HA_ATOMIC_STORE(val, new) ({*(val) = new;})
#define HA_ATOMIC_UPDATE_MAX(val, new) \
({ \
- typeof(*(val)) __new = (new); \
+ typeof(*(val)) __new_max = (new); \
\
- if (*(val) < __new) \
- *(val) = __new; \
+ if (*(val) < __new_max) \
+ *(val) = __new_max; \
*(val); \
})
#define HA_ATOMIC_UPDATE_MIN(val, new) \
({ \
- typeof(*(val)) __new = (new); \
+ typeof(*(val)) __new_min = (new); \
\
- if (*(val) > __new) \
- *(val) = __new; \
+ if (*(val) > __new_min) \
+ *(val) = __new_min; \
*(val); \
})
@@ -124,38 +124,38 @@ extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the threa
* but only if it differs from the expected one. If it's the same it's a race
* thus we try again to avoid confusing a possibly sensitive caller.
*/
-#define HA_ATOMIC_CAS(val, old, new) \
- ({ \
- typeof((val)) __val = (val); \
- typeof((old)) __oldp = (old); \
- typeof(*(old)) __oldv; \
- typeof((new)) __new = (new); \
- int __ret; \
- do { \
- __oldv = *__val; \
- __ret = __sync_bool_compare_and_swap(__val, *__oldp, __new); \
- } while (!__ret && *__oldp == __oldv); \
- if (!__ret) \
- *__oldp = __oldv; \
- __ret; \
+#define HA_ATOMIC_CAS(val, old, new) \
+ ({ \
+ typeof((val)) __val_cas = (val); \
+ typeof((old)) __oldp_cas = (old); \
+ typeof(*(old)) __oldv_cas; \
+ typeof((new)) __new_cas = (new); \
+ int __ret_cas; \
+ do { \
+ __oldv_cas = *__val_cas; \
+ __ret_cas = __sync_bool_compare_and_swap(__val_cas, *__oldp_cas, __new_cas); \
+ } while (!__ret_cas && *__oldp_cas == __oldv_cas); \
+ if (!__ret_cas) \
+ *__oldp_cas = __oldv_cas; \
+ __ret_cas; \
})
-#define HA_ATOMIC_XCHG(val, new) \
- ({ \
- typeof((val)) __val = (val); \
- typeof(*(val)) __old; \
- typeof((new)) __new = (new); \
- do { __old = *__val; \
- } while (!__sync_bool_compare_and_swap(__val, __old, __new)); \
- __old; \
+#define HA_ATOMIC_XCHG(val, new) \
+ ({ \
+ typeof((val)) __val_xchg = (val); \
+ typeof(*(val)) __old_xchg; \
+ typeof((new)) __new_xchg = (new); \
+ do { __old_xchg = *__val_xchg; \
+ } while (!__sync_bool_compare_and_swap(__val_xchg, __old_xchg, __new_xchg)); \
+ __old_xchg; \
})
-#define HA_ATOMIC_STORE(val, new) \
- ({ \
- typeof((val)) __val = (val); \
- typeof(*(val)) __old; \
- typeof((new)) __new = (new); \
- do { __old = *__val; \
- } while (!__sync_bool_compare_and_swap(__val, __old, __new)); \
+#define HA_ATOMIC_STORE(val, new) \
+ ({ \
+ typeof((val)) __val_store = (val); \
+ typeof(*(val)) __old_store; \
+ typeof((new)) __new_store = (new); \
+ do { __old_store = *__val_store; \
+ } while (!__sync_bool_compare_and_swap(__val_store, __old_store, __new_store)); \
})
#else
/* gcc >= 4.7 */
@@ -170,19 +170,21 @@ extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the threa
#define HA_ATOMIC_UPDATE_MAX(val, new) \
({ \
- typeof(*(val)) __old = *(val); \
- typeof(*(val)) __new = (new); \
+ typeof(*(val)) __old_max = *(val); \
+ typeof(*(val)) __new_max = (new); \
\
- while (__old < __new && !HA_ATOMIC_CAS(val, &__old, __new)); \
- (*val); \
+ while (__old_max < __new_max && \
+ !HA_ATOMIC_CAS(val, &__old_max, __new_max)); \
+ *(val); \
})
#define HA_ATOMIC_UPDATE_MIN(val, new) \
({ \
- typeof((*val)) __old = *(val); \
- typeof((*val)) __new = (new); \
+ typeof(*(val)) __old_min = *(val); \
+ typeof(*(val)) __new_min = (new); \
\
- while (__old > __new && !HA_ATOMIC_CAS(val, &__old, __new)); \
- (*val); \
+ while (__old_min > __new_min && \
+ !HA_ATOMIC_CAS(val, &__old_min, __new_min)); \
+ *(val); \
})
#define HA_BARRIER() pl_barrier()
--
2.14.3
