From c3b595825583386bbc28fcd0c77c5ff926fcf345 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Mon, 27 May 2019 17:37:20 +0200 Subject: [PATCH] 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 --- include/common/hathreads.h | 17 ++++++++++++++++- src/fd.c | 2 +- 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/include/common/hathreads.h b/include/common/hathreads.h index 268dd6349..0ba56d0d0 100644 --- a/include/common/hathreads.h +++ b/include/common/hathreads.h @@ -77,7 +77,19 @@ extern THREAD_LOCAL struct thread_info *ti; /* thread_info for the current threa #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 @@ static inline unsigned long thread_isolated() __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 @@ static inline unsigned long thread_isolated() #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 @@ static inline unsigned long thread_isolated() * 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) diff --git a/src/fd.c b/src/fd.c index d87dddc2a..e71c2ee8d 100644 --- a/src/fd.c +++ b/src/fd.c @@ -272,7 +272,7 @@ lock_self: #ifdef HA_CAS_IS_8B unlikely(!_HA_ATOMIC_CAS(((void **)(void *)&_GET_NEXT(fd, off)), ((void **)(void *)&cur_list), (*(void **)(void *)&next_list)))) #else - unlikely(!_HA_ATOMIC_DWCAS(((void **)(void *)&_GET_NEXT(fd, off)), ((void **)(void *)&cur_list), (*(void **)(void *)&next_list)))) + unlikely(!_HA_ATOMIC_DWCAS(((void *)&_GET_NEXT(fd, off)), ((void *)&cur_list), ((void *)&next_list)))) #endif ; next = cur_list.next;