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| author | Ivan Maidanski <ivmai@mail.ru> | 2017-12-21 02:25:48 +0300 |
|---|---|---|
| committer | Ivan Maidanski <ivmai@mail.ru> | 2017-12-21 02:25:48 +0300 |
| commit | 3aefd4e732f2894c31ee74315c3d65644a1f4ac1 (patch) | |
| tree | b55769b5629ae8d29e868f16d71b34f156ac471d /src | |
| parent | ca02cd7b1434107ca470f62cb046d1595d5a2a84 (diff) | |
| download | libatomic_ops-3aefd4e732f2894c31ee74315c3d65644a1f4ac1.tar.gz | |
Workaround TSan false positive in AO_stack_pop_explicit_aux_acquire
(fix commits c058d9d, 6ffda1db)
The TSan-related workaround in AO_malloc is no longer needed.
* src/atomic_ops_malloc.c [AO_THREAD_SANITIZER
&& AO_USE_ALMOST_LOCK_FREE] (AO_malloc): Do not use AO_store (always
use *result=log_sz); remove comment.
* src/atomic_ops_stack.c [AO_USE_ALMOST_LOCK_FREE
&& AO_THREAD_SANITIZER] (AO_load_next): New static function (with
AO_ATTR_NO_SANITIZE_THREAD attribute); add comments.
* src/atomic_ops_stack.c [AO_USE_ALMOST_LOCK_FREE
&& !AO_THREAD_SANITIZER] (AO_load_next): Define to AO_load.
* src/atomic_ops_stack.c [AO_USE_ALMOST_LOCK_FREE]
(AO_stack_pop_explicit_aux_acquire): Replace AO_load(first_ptr) with
AO_load_next(first_ptr).
Diffstat (limited to 'src')
| -rw-r--r-- | src/atomic_ops_malloc.c | 7 | ||||
| -rw-r--r-- | src/atomic_ops_stack.c | 17 |
2 files changed, 17 insertions, 7 deletions
diff --git a/src/atomic_ops_malloc.c b/src/atomic_ops_malloc.c index a2016ea..f86585d 100644 --- a/src/atomic_ops_malloc.c +++ b/src/atomic_ops_malloc.c @@ -336,12 +336,7 @@ AO_malloc(size_t sz) add_chunk_as(chunk, log_sz); result = AO_stack_pop(AO_free_list+log_sz); } -# if defined(AO_THREAD_SANITIZER) && defined(AO_USE_ALMOST_LOCK_FREE) - /* A data race with AO_stack_pop() called above is a false positive. */ - AO_store(result, log_sz); -# else - *result = log_sz; -# endif + *result = log_sz; # ifdef AO_TRACE_MALLOC fprintf(stderr, "%p: AO_malloc(%lu) = %p\n", (void *)pthread_self(), (unsigned long)sz, (void *)(result + 1)); diff --git a/src/atomic_ops_stack.c b/src/atomic_ops_stack.c index 5219fdf..e167d36 100644 --- a/src/atomic_ops_stack.c +++ b/src/atomic_ops_stack.c @@ -122,6 +122,21 @@ void AO_stack_push_explicit_aux_release(volatile AO_t *list, AO_t *x, # define PRECHECK(a) #endif +/* This function is used before CAS in the below AO_stack_pop() and the */ +/* data race (reported by TSan) is OK because it results in a retry. */ +#ifdef AO_THREAD_SANITIZER + AO_ATTR_NO_SANITIZE_THREAD + static AO_t AO_load_next(volatile AO_t *first_ptr) + { + /* Assuming an architecture on which loads of word type are atomic. */ + /* AO_load cannot be used here because it cannot be instructed to */ + /* suppress the warning about the race. */ + return *first_ptr; + } +#else +# define AO_load_next AO_load +#endif + AO_t * AO_stack_pop_explicit_aux_acquire(volatile AO_t *list, AO_stack_aux * a) { @@ -176,7 +191,7 @@ AO_stack_pop_explicit_aux_acquire(volatile AO_t *list, AO_stack_aux * a) goto retry; } first_ptr = AO_REAL_NEXT_PTR(first); - next = AO_load(first_ptr); + next = AO_load_next(first_ptr); # if defined(__alpha__) && (__GNUC__ == 4) if (!AO_compare_and_swap_release(list, first, next)) # else |