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Fix fc_atomic_ptr_get and use. 

Before this change building with ThreadSanitizer and running
test/test-pthread generated a large number of threading issues. These
mostly stemmed from fc_atomic_ptr_get not doing an atomic load and using
"acquire load" instead of "load acquire". After making these changes it
was still necessary to use fc_atomic_ptr_get where it was needed.

This also documents the current memory barrier requirements for the
atomic primitives.
This commit is contained in:
Ben Wagner 2020-10-29 22:29:00 -04:00 committed by Akira TAGOH
parent 4ee4347691
commit 447b9ccc7d
3 changed files with 25 additions and 18 deletions
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34
src/fcatomic.h
View File

@ -43,28 +43,23 @@
#if 0
typedef <type> fc_atomic_int_t;
#define FC_ATOMIC_INT_FORMAT "<printf format for fc_atomic_int_t>"
#define fc_atomic_int_add(AI, V) o = (AI), (AI) += (V), o // atomic acquire/release
#define fc_atomic_ptr_get(P) *(P) // atomic acquire
#define fc_atomic_ptr_cmpexch(P,O,N) *(P) == (O) ? (*(P) = (N), FcTrue) : FcFalse // atomic release
#elif !defined(FC_NO_MT) && defined(_MSC_VER) || defined(__MINGW32__)
#include "fcwindows.h"
/* MinGW has a convoluted history of supporting MemoryBarrier
* properly. As such, define a function to wrap the whole
* thing. */
static inline void _FCMemoryBarrier (void) {
#if !defined(MemoryBarrier)
long dummy = 0;
InterlockedExchange (&dummy, 1);
#else
MemoryBarrier ();
#endif
}
typedef LONG fc_atomic_int_t;
#define FC_ATOMIC_INT_FORMAT "ld"
#define fc_atomic_int_add(AI, V) InterlockedExchangeAdd (&(AI), (V))
#define fc_atomic_ptr_get(P) (_FCMemoryBarrier (), (void *) *(P))
#define fc_atomic_ptr_get(P) (InterlockedCompareExchangePointerAcquire ((void **) (P), NULL, NULL))
#define fc_atomic_ptr_cmpexch(P,O,N) (InterlockedCompareExchangePointer ((void **) (P), (void *) (N), (void *) (O)) == (void *) (O))
@ -77,20 +72,29 @@ typedef int fc_atomic_int_t;
#define FC_ATOMIC_INT_FORMAT "d"
#define fc_atomic_int_add(AI, V) (OSAtomicAdd32Barrier ((V), &(AI)) - (V))
#define fc_atomic_ptr_get(P) (OSMemoryBarrier (), (void *) *(P))
#if (MAC_OS_X_VERSION_MIN_REQUIRED > MAC_OS_X_VERSION_10_4 || __IPHONE_OS_VERSION_MIN_REQUIRED >= 20100)
#if SIZEOF_VOID_P == 8
#define fc_atomic_ptr_get(P) OSAtomicAdd64Barrier (0, (int64_t*)(P))
#elif SIZEOF_VOID_P == 4
#define fc_atomic_ptr_get(P) OSAtomicAdd32Barrier (0, (int32_t*)(P))
#else
#error "SIZEOF_VOID_P not 4 or 8 (assumes CHAR_BIT is 8)"
#endif
#define fc_atomic_ptr_cmpexch(P,O,N) OSAtomicCompareAndSwapPtrBarrier ((void *) (O), (void *) (N), (void **) (P))
#else
#error "Your macOS / iOS targets are too old"
#endif
#elif !defined(FC_NO_MT) && defined(HAVE_INTEL_ATOMIC_PRIMITIVES)
typedef int fc_atomic_int_t;
#define FC_ATOMIC_INT_FORMAT "d"
#define fc_atomic_int_add(AI, V) __sync_fetch_and_add (&(AI), (V))
#define fc_atomic_ptr_get(P) (void *) (__sync_synchronize (), *(P))
#define fc_atomic_ptr_get(P) (void *) (__sync_fetch_and_add ((P), 0))
#define fc_atomic_ptr_cmpexch(P,O,N) __sync_bool_compare_and_swap ((P), (O), (N))

4
src/fccache.c
View File

@ -509,7 +509,9 @@ retry:
static void
unlock_cache (void)
{
FcMutexUnlock (cache_lock);
FcMutex *lock;
lock = fc_atomic_ptr_get (&cache_lock);
FcMutexUnlock (lock);
}
static void

5
src/fccfg.c
View File

@ -67,14 +67,15 @@ retry:
static void
unlock_config (void)
{
FcMutexUnlock (_lock);
FcMutex *lock;
lock = fc_atomic_ptr_get (&_lock);
FcMutexUnlock (lock);
}
static void
free_lock (void)
{
FcMutex *lock;
lock = fc_atomic_ptr_get (&_lock);
if (lock && fc_atomic_ptr_cmpexch (&_lock, lock, NULL))
{