+++ /dev/null
-/*
- * Copyright (c) 1999-2007 Apple Inc. All Rights Reserved.
- *
- * @APPLE_LICENSE_HEADER_START@
- *
- * This file contains Original Code and/or Modifications of Original Code
- * as defined in and that are subject to the Apple Public Source License
- * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
- *
- * The Original Code and all software distributed under the License are
- * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
- * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
- * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- * Please see the License for the specific language governing rights and
- * limitations under the License.
- *
- * @APPLE_LICENSE_HEADER_END@
- */
-
-#include "objc-private.h"
-#include "objc-sync.h"
-
-//
-// Allocate a lock only when needed. Since few locks are needed at any point
-// in time, keep them on a single list.
-//
-
-
-typedef struct SyncData {
- struct SyncData* nextData;
- id object;
- int threadCount; // number of THREADS using this block
- recursive_mutex_t mutex;
-} SyncData;
-
-typedef struct {
- SyncData *data;
- unsigned int lockCount; // number of times THIS THREAD locked this block
-} SyncCacheItem;
-
-typedef struct SyncCache {
- unsigned int allocated;
- unsigned int used;
- SyncCacheItem list[0];
-} SyncCache;
-
-/*
- Fast cache: two fixed pthread keys store a single SyncCacheItem.
- This avoids malloc of the SyncCache for threads that only synchronize
- a single object at a time.
- SYNC_DATA_DIRECT_KEY == SyncCacheItem.data
- SYNC_COUNT_DIRECT_KEY == SyncCacheItem.lockCount
- */
-
-typedef struct {
- SyncData *data;
- OSSpinLock lock;
-
- char align[64 - sizeof (OSSpinLock) - sizeof (SyncData *)];
-} SyncList __attribute__((aligned(64)));
-// aligned to put locks on separate cache lines
-
-// Use multiple parallel lists to decrease contention among unrelated objects.
-#define COUNT 16
-#define HASH(obj) ((((uintptr_t)(obj)) >> 5) & (COUNT - 1))
-#define LOCK_FOR_OBJ(obj) sDataLists[HASH(obj)].lock
-#define LIST_FOR_OBJ(obj) sDataLists[HASH(obj)].data
-static SyncList sDataLists[COUNT];
-
-
-enum usage { ACQUIRE, RELEASE, CHECK };
-
-static SyncCache *fetch_cache(BOOL create)
-{
- _objc_pthread_data *data;
-
- data = _objc_fetch_pthread_data(create);
- if (!data) return NULL;
-
- if (!data->syncCache) {
- if (!create) {
- return NULL;
- } else {
- int count = 4;
- data->syncCache = calloc(1, sizeof(SyncCache) +
- count*sizeof(SyncCacheItem));
- data->syncCache->allocated = count;
- }
- }
-
- // Make sure there's at least one open slot in the list.
- if (data->syncCache->allocated == data->syncCache->used) {
- data->syncCache->allocated *= 2;
- data->syncCache =
- realloc(data->syncCache, sizeof(SyncCache)
- + data->syncCache->allocated * sizeof(SyncCacheItem));
- }
-
- return data->syncCache;
-}
-
-
-PRIVATE_EXTERN void _destroySyncCache(struct SyncCache *cache)
-{
- if (cache) free(cache);
-}
-
-
-static SyncData* id2data(id object, enum usage why)
-{
- OSSpinLock *lockp = &LOCK_FOR_OBJ(object);
- SyncData **listp = &LIST_FOR_OBJ(object);
- SyncData* result = NULL;
-
-#if SUPPORT_DIRECT_THREAD_KEYS
- // Check per-thread single-entry fast cache for matching object
- BOOL fastCacheOccupied = NO;
- SyncData *data = tls_get_direct(SYNC_DATA_DIRECT_KEY);
- if (data) {
- fastCacheOccupied = YES;
-
- if (data->object == object) {
- // Found a match in fast cache.
- uintptr_t lockCount;
-
- result = data;
- lockCount = (uintptr_t)tls_get_direct(SYNC_COUNT_DIRECT_KEY);
- require_action_string(result->threadCount > 0, fastcache_done,
- result = NULL, "id2data fastcache is buggy");
- require_action_string(lockCount > 0, fastcache_done,
- result = NULL, "id2data fastcache is buggy");
-
- switch(why) {
- case ACQUIRE: {
- lockCount++;
- tls_set_direct(SYNC_COUNT_DIRECT_KEY, (void*)lockCount);
- break;
- }
- case RELEASE:
- lockCount--;
- tls_set_direct(SYNC_COUNT_DIRECT_KEY, (void*)lockCount);
- if (lockCount == 0) {
- // remove from fast cache
- tls_set_direct(SYNC_DATA_DIRECT_KEY, NULL);
- // atomic because may collide with concurrent ACQUIRE
- OSAtomicDecrement32Barrier(&result->threadCount);
- }
- break;
- case CHECK:
- // do nothing
- break;
- }
-
- fastcache_done:
- return result;
- }
- }
-#endif
-
- // Check per-thread cache of already-owned locks for matching object
- SyncCache *cache = fetch_cache(NO);
- if (cache) {
- unsigned int i;
- for (i = 0; i < cache->used; i++) {
- SyncCacheItem *item = &cache->list[i];
- if (item->data->object != object) continue;
-
- // Found a match.
- result = item->data;
- require_action_string(result->threadCount > 0, cache_done,
- result = NULL, "id2data cache is buggy");
- require_action_string(item->lockCount > 0, cache_done,
- result = NULL, "id2data cache is buggy");
-
- switch(why) {
- case ACQUIRE:
- item->lockCount++;
- break;
- case RELEASE:
- item->lockCount--;
- if (item->lockCount == 0) {
- // remove from per-thread cache
- cache->list[i] = cache->list[--cache->used];
- // atomic because may collide with concurrent ACQUIRE
- OSAtomicDecrement32Barrier(&result->threadCount);
- }
- break;
- case CHECK:
- // do nothing
- break;
- }
-
- cache_done:
- return result;
- }
- }
-
- // Thread cache didn't find anything.
- // Walk in-use list looking for matching object
- // Spinlock prevents multiple threads from creating multiple
- // locks for the same new object.
- // We could keep the nodes in some hash table if we find that there are
- // more than 20 or so distinct locks active, but we don't do that now.
-
- OSSpinLockLock(lockp);
-
- {
- SyncData* p;
- SyncData* firstUnused = NULL;
- for (p = *listp; p != NULL; p = p->nextData) {
- if ( p->object == object ) {
- result = p;
- // atomic because may collide with concurrent RELEASE
- OSAtomicIncrement32Barrier(&result->threadCount);
- goto done;
- }
- if ( (firstUnused == NULL) && (p->threadCount == 0) )
- firstUnused = p;
- }
-
- // no SyncData currently associated with object
- if ( (why == RELEASE) || (why == CHECK) )
- goto done;
-
- // an unused one was found, use it
- if ( firstUnused != NULL ) {
- result = firstUnused;
- result->object = object;
- result->threadCount = 1;
- goto done;
- }
- }
-
- // malloc a new SyncData and add to list.
- // XXX calling malloc with a global lock held is bad practice,
- // might be worth releasing the lock, mallocing, and searching again.
- // But since we never free these guys we won't be stuck in malloc very often.
- result = (SyncData*)calloc(sizeof(SyncData), 1);
- result->object = object;
- result->threadCount = 1;
- recursive_mutex_init(&result->mutex);
- result->nextData = *listp;
- *listp = result;
-
- done:
- OSSpinLockUnlock(lockp);
- if (result) {
- // Only new ACQUIRE should get here.
- // All RELEASE and CHECK and recursive ACQUIRE are
- // handled by the per-thread caches above.
-
- require_string(result != NULL, really_done, "id2data is buggy");
- require_action_string(why == ACQUIRE, really_done,
- result = NULL, "id2data is buggy");
- require_action_string(result->object == object, really_done,
- result = NULL, "id2data is buggy");
-
-#if SUPPORT_DIRECT_THREAD_KEYS
- if (!fastCacheOccupied) {
- // Save in fast thread cache
- tls_set_direct(SYNC_DATA_DIRECT_KEY, result);
- tls_set_direct(SYNC_COUNT_DIRECT_KEY, (void*)1);
- } else
-#endif
- {
- // Save in thread cache
- if (!cache) cache = fetch_cache(YES);
- cache->list[cache->used].data = result;
- cache->list[cache->used].lockCount = 1;
- cache->used++;
- }
- }
-
- really_done:
- return result;
-}
-
-
-BREAKPOINT_FUNCTION(
- void objc_sync_nil(void)
-);
-
-
-// Begin synchronizing on 'obj'.
-// Allocates recursive mutex associated with 'obj' if needed.
-// Returns OBJC_SYNC_SUCCESS once lock is acquired.
-int objc_sync_enter(id obj)
-{
- int result = OBJC_SYNC_SUCCESS;
-
- if (obj) {
- SyncData* data = id2data(obj, ACQUIRE);
- require_action_string(data != NULL, done, result = OBJC_SYNC_NOT_INITIALIZED, "id2data failed");
-
- result = recursive_mutex_lock(&data->mutex);
- require_noerr_string(result, done, "mutex_lock failed");
- } else {
- // @synchronized(nil) does nothing
- if (DebugNilSync) {
- _objc_inform("NIL SYNC DEBUG: @synchronized(nil); set a breakpoint on objc_sync_nil to debug");
- }
- objc_sync_nil();
- }
-
-done:
- return result;
-}
-
-
-// End synchronizing on 'obj'.
-// Returns OBJC_SYNC_SUCCESS or OBJC_SYNC_NOT_OWNING_THREAD_ERROR
-int objc_sync_exit(id obj)
-{
- int result = OBJC_SYNC_SUCCESS;
-
- if (obj) {
- SyncData* data = id2data(obj, RELEASE);
- require_action_string(data != NULL, done, result = OBJC_SYNC_NOT_OWNING_THREAD_ERROR, "id2data failed");
-
- result = recursive_mutex_unlock(&data->mutex);
- require_noerr_string(result, done, "mutex_unlock failed");
- } else {
- // @synchronized(nil) does nothing
- }
-
-done:
- if ( result == RECURSIVE_MUTEX_NOT_LOCKED )
- result = OBJC_SYNC_NOT_OWNING_THREAD_ERROR;
-
- return result;
-}
-
projects / apple / objc4.git / blobdiff