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Further atomic ops portability improvements and bug fixes.

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* Don't play tricks for a more efficient pg_atomic_clear_flag() in the
  generic gcc implementation. The old version was broken on gcc < 4.7
  on !x86 platforms. Per buildfarm member chipmunk.
* Make usage of __atomic() fences depend on HAVE_GCC__ATOMIC_INT32_CAS
  instead of HAVE_GCC__ATOMIC_INT64_CAS - there's platforms with 32bit
  support that don't support 64bit atomics.
* Blindly fix two superflous #endif in generic-xlc.h
* Check for --disable-atomics in platforms but x86.
This commit is contained in:
Andres Freund
2014-09-26 15:55:44 +02:00
parent a30199b01b
commit f9f07411a5
6 changed files with 51 additions and 13 deletions
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14
src/include/port/atomics/generic-gcc.h
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@@ -40,19 +40,19 @@
* definitions where possible, and use this only as a fallback.
*/
#if !defined(pg_memory_barrier_impl)
# if defined(HAVE_GCC__ATOMIC_INT64_CAS)
# if defined(HAVE_GCC__ATOMIC_INT32_CAS)
# define pg_memory_barrier_impl() __atomic_thread_fence(__ATOMIC_SEQ_CST)
# elif (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1))
# define pg_memory_barrier_impl() __sync_synchronize()
# endif
#endif /* !defined(pg_memory_barrier_impl) */
#if !defined(pg_read_barrier_impl) && defined(HAVE_GCC__ATOMIC_INT64_CAS)
#if !defined(pg_read_barrier_impl) && defined(HAVE_GCC__ATOMIC_INT32_CAS)
/* acquire semantics include read barrier semantics */
# define pg_read_barrier_impl() __atomic_thread_fence(__ATOMIC_ACQUIRE)
#endif
#if !defined(pg_write_barrier_impl) && defined(HAVE_GCC__ATOMIC_INT64_CAS)
#if !defined(pg_write_barrier_impl) && defined(HAVE_GCC__ATOMIC_INT32_CAS)
/* release semantics include write barrier semantics */
# define pg_write_barrier_impl() __atomic_thread_fence(__ATOMIC_RELEASE)
#endif
@@ -139,13 +139,7 @@ pg_atomic_unlocked_test_flag_impl(volatile pg_atomic_flag *ptr)
static inline void
pg_atomic_clear_flag_impl(volatile pg_atomic_flag *ptr)
{
/*
* XXX: It would be nicer to use __sync_lock_release here, but gcc insists
* on making that an atomic op which is far to expensive and a stronger
* guarantee than what we actually need.
*/
pg_write_barrier_impl();
ptr->value = 0;
__sync_lock_release(&ptr->value);
}
#endif