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[atomic] Fix get() impl 

Originally, glib's atomic_get was implemented as "memory_barrier; load".
I copied this into cairo, fontconfig, and harfbuzz.  However, that's
wrong.  Correct way is "load; memory_barrier".  The details are long
and hard to fully grasp.  Best to read:

  https://www.kernel.org/doc/Documentation/memory-barriers.txt

Also see my report against GNOME:

  https://gitlab.gnome.org/GNOME/glib/issues/1449

Note that this is irrelevant if C++11-like atomic ops are available.
This commit is contained in:
Behdad Esfahbod 2018-07-31 22:51:38 -07:00
parent d7a15799d4
commit 896ff15ae6
1 changed files with 17 additions and 11 deletions
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28
src/hb-atomic-private.hh
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@ -89,11 +89,10 @@ _hb_atomic_ptr_impl_cmplexch (const void **P, const void *O_, const void *N)
#include <windows.h>
/* MinGW has a convoluted history of supporting MemoryBarrier
* properly. As such, define a function to wrap the whole
* thing. */
static inline void _HBMemoryBarrier (void) {
static inline void _hb_memory_barrier (void)
{
#if !defined(MemoryBarrier)
/* MinGW has a convoluted history of supporting MemoryBarrier. */
long dummy = 0;
InterlockedExchange (&dummy, 1);
#else
@ -104,7 +103,6 @@ static inline void _HBMemoryBarrier (void) {
typedef LONG hb_atomic_int_impl_t;
#define hb_atomic_int_impl_add(AI, V) InterlockedExchangeAdd ((AI), (V))
#define hb_atomic_ptr_impl_get(P) (_HBMemoryBarrier (), (void *) *(P))
#define hb_atomic_ptr_impl_cmpexch(P,O,N) (InterlockedCompareExchangePointer ((void **) (P), (void *) (N), (void *) (O)) == (void *) (O))
@ -113,7 +111,8 @@ typedef LONG hb_atomic_int_impl_t;
typedef int hb_atomic_int_impl_t;
#define hb_atomic_int_impl_add(AI, V) __sync_fetch_and_add ((AI), (V))
#define hb_atomic_ptr_impl_get(P) (void *) (__sync_synchronize (), *(P))
static inline void _hb_memory_barrier (void) { __sync_synchronize (); }
#define hb_atomic_ptr_impl_cmpexch(P,O,N) __sync_bool_compare_and_swap ((P), (O), (N))
@ -125,7 +124,8 @@ typedef int hb_atomic_int_impl_t;
typedef unsigned int hb_atomic_int_impl_t;
#define hb_atomic_int_impl_add(AI, V) ( ({__machine_rw_barrier ();}), atomic_add_int_nv ((AI), (V)) - (V))
#define hb_atomic_ptr_impl_get(P) ( ({__machine_rw_barrier ();}), (void *) *(P))
static inline void _hb_memory_barrier (void) { __machine_rw_barrier (); }
#define hb_atomic_ptr_impl_cmpexch(P,O,N) ( ({__machine_rw_barrier ();}), atomic_cas_ptr ((void **) (P), (void *) (O), (void *) (N)) == (void *) (O) ? true : false)
@ -142,7 +142,8 @@ typedef unsigned int hb_atomic_int_impl_t;
typedef int32_t hb_atomic_int_impl_t;
#define hb_atomic_int_impl_add(AI, V) (OSAtomicAdd32Barrier ((V), (AI)) - (V))
#define hb_atomic_ptr_impl_get(P) (OSMemoryBarrier (), (void *) *(P))
static inline void _hb_memory_barrier (void) { OSMemoryBarrier (); }
#if (MAC_OS_X_VERSION_MIN_REQUIRED > MAC_OS_X_VERSION_10_4 || __IPHONE_VERSION_MIN_REQUIRED >= 20100)
#define hb_atomic_ptr_impl_cmpexch(P,O,N) OSAtomicCompareAndSwapPtrBarrier ((void *) (O), (void *) (N), (void **) (P))
#else
@ -175,7 +176,8 @@ static inline int _hb_compare_and_swaplp(volatile long* P, long O, long N) {
typedef int hb_atomic_int_impl_t;
#define hb_atomic_int_impl_add(AI, V) _hb_fetch_and_add ((AI), (V))
#define hb_atomic_ptr_impl_get(P) (__sync(), (void *) *(P))
static inline void _hb_memory_barrier (void) { __sync(); }
#define hb_atomic_ptr_impl_cmpexch(P,O,N) _hb_compare_and_swaplp ((long*)(P), (long)(O), (long)(N))
#elif !defined(HB_NO_MT)
@ -185,7 +187,7 @@ typedef int hb_atomic_int_impl_t;
typedef volatile int hb_atomic_int_impl_t;
#define hb_atomic_int_impl_add(AI, V) ((*(AI) += (V)) - (V))
#define hb_atomic_ptr_impl_get(P) ((void *) *(P))
static inline void _hb_memory_barrier (void) {}
#define hb_atomic_ptr_impl_cmpexch(P,O,N) (* (void * volatile *) (P) == (void *) (O) ? (* (void * volatile *) (P) = (void *) (N), true) : false)
@ -194,7 +196,8 @@ typedef volatile int hb_atomic_int_impl_t;
typedef int hb_atomic_int_impl_t;
#define hb_atomic_int_impl_add(AI, V) ((*(AI) += (V)) - (V))
#define hb_atomic_ptr_impl_get(P) ((void *) *(P))
static inline void _hb_memory_barrier (void) {}
#define hb_atomic_ptr_impl_cmpexch(P,O,N) (* (void **) (P) == (void *) (O) ? (* (void **) (P) = (void *) (N), true) : false)
@ -210,6 +213,9 @@ typedef int hb_atomic_int_impl_t;
#ifndef hb_atomic_int_impl_get_relaxed
#define hb_atomic_int_impl_get_relaxed(AI) (*(AI))
#endif
#ifndef hb_atomic_ptr_impl_get
inline void *hb_atomic_ptr_impl_get (void **P) { void *v = *P; _hb_memory_barrier (); return v; }
#endif
struct hb_atomic_int_t