BUG/MEDIUM: threads: Fix the max/min calculation because of name clashes

With gcc < 4.7, when HAProxy is built with threads, the macros
HA_ATOMIC_CAS/XCHG/STORE relies on the legacy __sync 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.

diff --git a/include/common/hathreads.h b/include/common/hathreads.h
index 15b8ce2c18988ec9bfda18d78a511b5d6aff3f07..0f10b48ca013aebca0dafa3c3bb3a39202d592ce 100644 (file)
--- a/include/common/hathreads.h
+++ b/include/common/hathreads.h
@@ -41,44 +41,44 @@ 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_BTS(val, bit)                                                \
        ({                                                              \
-               typeof((val)) __p = (val);                              \
-               typeof(*__p)  __b = (1UL << (bit));                     \
-               typeof(*__p)  __t = *__p & __b;                         \
-               if (!__t)                                               \
-                       *__p |= __b;                                    \
-               __t;                                                    \
+               typeof((val)) __p_bts = (val);                          \
+               typeof(*__p_bts)  __b_bts = (1UL << (bit));             \
+               typeof(*__p_bts)  __t_bts = *__p_bts & __b_bts;         \
+               if (!__t_bts)                                           \
+                       *__p_bts |= __b_bts;                            \
+               __t_bts;                                                \
        })
 #define HA_ATOMIC_BTR(val, bit)                                                \
        ({                                                              \
-               typeof((val)) __p = (val);                              \
-               typeof(*__p)  __b = (1UL << (bit));                     \
-               typeof(*__p)  __t = *__p & __b;                         \
-               if (__t)                                                \
-                       *__p &= ~__b;                                   \
-               __t;                                                    \
+               typeof((val)) __p_btr = (val);                          \
+               typeof(*__p_btr)  __b_btr = (1UL << (bit));             \
+               typeof(*__p_btr)  __t_btr = *__p_btr & __b_btr;         \
+               if (__t_btr)                                            \
+                       *__p_btr &= ~__b_btr;                           \
+               __t_btr;                                                \
        })
 #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);                                                 \
        })
 
@@ -150,51 +150,51 @@ static inline void __ha_barrier_full(void)
  * 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_BTS(val, bit)                                                \
        ({                                                              \
-               typeof(*(val)) __b = (1UL << (bit));                    \
-               __sync_fetch_and_or((val), __b) & __b;                  \
+               typeof(*(val)) __b_bts = (1UL << (bit));                \
+               __sync_fetch_and_or((val), __b_bts) & __b_bts;          \
        })
 
 #define HA_ATOMIC_BTR(val, bit)                                                \
        ({                                                              \
-               typeof(*(val)) __b = (1UL << (bit));                    \
-               __sync_fetch_and_and((val), ~__b) & __b;                \
+               typeof(*(val)) __b_btr = (1UL << (bit));                \
+               __sync_fetch_and_and((val), ~__b_btr) & __b_btr;        \
        })
 
-#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 */
@@ -205,14 +205,14 @@ static inline void __ha_barrier_full(void)
 #define HA_ATOMIC_OR(val, flags)     __atomic_or_fetch(val,  flags, 0)
 #define HA_ATOMIC_BTS(val, bit)                                                \
        ({                                                              \
-               typeof(*(val)) __b = (1UL << (bit));                    \
-               __sync_fetch_and_or((val), __b) & __b;                  \
+               typeof(*(val)) __b_bts = (1UL << (bit));                \
+               __sync_fetch_and_or((val), __b_bts) & __b_bts;          \
        })
 
 #define HA_ATOMIC_BTR(val, bit)                                                \
        ({                                                              \
-               typeof(*(val)) __b = (1UL << (bit));                    \
-               __sync_fetch_and_and((val), ~__b) & __b;                \
+               typeof(*(val)) __b_btr = (1UL << (bit));                \
+               __sync_fetch_and_and((val), ~__b_btr) & __b_btr;        \
        })
 
 #define HA_ATOMIC_XCHG(val, new)     __atomic_exchange_n(val, new, 0)
@@ -221,19 +221,21 @@ static inline void __ha_barrier_full(void)
 
 #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()