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Diffstat (limited to 'tools/build/src/engine/boehm_gc/specific.c')
| -rw-r--r-- | tools/build/src/engine/boehm_gc/specific.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/tools/build/src/engine/boehm_gc/specific.c b/tools/build/src/engine/boehm_gc/specific.c new file mode 100644 index 000000000..b8ea49dd3 --- /dev/null +++ b/tools/build/src/engine/boehm_gc/specific.c @@ -0,0 +1,165 @@ +/* + * Copyright (c) 2000 by Hewlett-Packard Company. All rights reserved. + * + * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED + * OR IMPLIED. ANY USE IS AT YOUR OWN RISK. + * + * Permission is hereby granted to use or copy this program + * for any purpose, provided the above notices are retained on all copies. + * Permission to modify the code and to distribute modified code is granted, + * provided the above notices are retained, and a notice that the code was + * modified is included with the above copyright notice. + */ + +#include "private/gc_priv.h" /* For configuration, pthreads.h. */ +#include "private/thread_local_alloc.h" + /* To determine type of tsd impl. */ + /* Includes private/specific.h */ + /* if needed. */ + +#if defined(USE_CUSTOM_SPECIFIC) + +#include "atomic_ops.h" + +static tse invalid_tse = {INVALID_QTID, 0, 0, INVALID_THREADID}; + /* A thread-specific data entry which will never */ + /* appear valid to a reader. Used to fill in empty */ + /* cache entries to avoid a check for 0. */ + +int PREFIXED(key_create) (tsd ** key_ptr, void (* destructor)(void *)) { + int i; + tsd * result = (tsd *)MALLOC_CLEAR(sizeof (tsd)); + + /* A quick alignment check, since we need atomic stores */ + GC_ASSERT((unsigned long)(&invalid_tse.next) % sizeof(tse *) == 0); + if (0 == result) return ENOMEM; + pthread_mutex_init(&(result -> lock), NULL); + for (i = 0; i < TS_CACHE_SIZE; ++i) { + result -> cache[i] = &invalid_tse; + } +# ifdef GC_ASSERTIONS + for (i = 0; i < TS_HASH_SIZE; ++i) { + GC_ASSERT(result -> hash[i] == 0); + } +# endif + *key_ptr = result; + return 0; +} + +int PREFIXED(setspecific) (tsd * key, void * value) { + pthread_t self = pthread_self(); + int hash_val = HASH(self); + volatile tse * entry = (volatile tse *)MALLOC_CLEAR(sizeof (tse)); + + GC_ASSERT(self != INVALID_THREADID); + if (0 == entry) return ENOMEM; + pthread_mutex_lock(&(key -> lock)); + /* Could easily check for an existing entry here. */ + entry -> next = key -> hash[hash_val]; + entry -> thread = self; + entry -> value = value; + GC_ASSERT(entry -> qtid == INVALID_QTID); + /* There can only be one writer at a time, but this needs to be */ + /* atomic with respect to concurrent readers. */ + AO_store_release((volatile AO_t *)(key -> hash + hash_val), (AO_t)entry); + pthread_mutex_unlock(&(key -> lock)); + return 0; +} + +/* Remove thread-specific data for this thread. Should be called on */ +/* thread exit. */ +void PREFIXED(remove_specific) (tsd * key) { + pthread_t self = pthread_self(); + unsigned hash_val = HASH(self); + tse *entry; + tse **link = key -> hash + hash_val; + + pthread_mutex_lock(&(key -> lock)); + entry = *link; + while (entry != NULL && entry -> thread != self) { + link = &(entry -> next); + entry = *link; + } + /* Invalidate qtid field, since qtids may be reused, and a later */ + /* cache lookup could otherwise find this entry. */ + entry -> qtid = INVALID_QTID; + if (entry != NULL) { + *link = entry -> next; + /* Atomic! concurrent accesses still work. */ + /* They must, since readers don't lock. */ + /* We shouldn't need a volatile access here, */ + /* since both this and the preceding write */ + /* should become visible no later than */ + /* the pthread_mutex_unlock() call. */ + } + /* If we wanted to deallocate the entry, we'd first have to clear */ + /* any cache entries pointing to it. That probably requires */ + /* additional synchronization, since we can't prevent a concurrent */ + /* cache lookup, which should still be examining deallocated memory.*/ + /* This can only happen if the concurrent access is from another */ + /* thread, and hence has missed the cache, but still... */ + + /* With GC, we're done, since the pointers from the cache will */ + /* be overwritten, all local pointers to the entries will be */ + /* dropped, and the entry will then be reclaimed. */ + pthread_mutex_unlock(&(key -> lock)); +} + +/* Note that even the slow path doesn't lock. */ +void * PREFIXED(slow_getspecific) (tsd * key, unsigned long qtid, + tse * volatile * cache_ptr) { + pthread_t self = pthread_self(); + unsigned hash_val = HASH(self); + tse *entry = key -> hash[hash_val]; + + GC_ASSERT(qtid != INVALID_QTID); + while (entry != NULL && entry -> thread != self) { + entry = entry -> next; + } + if (entry == NULL) return NULL; + /* Set cache_entry. */ + entry -> qtid = qtid; + /* It's safe to do this asynchronously. Either value */ + /* is safe, though may produce spurious misses. */ + /* We're replacing one qtid with another one for the */ + /* same thread. */ + *cache_ptr = entry; + /* Again this is safe since pointer assignments are */ + /* presumed atomic, and either pointer is valid. */ + return entry -> value; +} + +#ifdef GC_ASSERTIONS + +/* Check that that all elements of the data structure associated */ +/* with key are marked. */ +void PREFIXED(check_tsd_marks) (tsd *key) +{ + int i; + tse *p; + + if (!GC_is_marked(GC_base(key))) { + ABORT("Unmarked thread-specific-data table"); + } + for (i = 0; i < TS_HASH_SIZE; ++i) { + for (p = key -> hash[i]; p != 0; p = p -> next) { + if (!GC_is_marked(GC_base(p))) { + GC_err_printf( + "Thread-specific-data entry at %p not marked\n",p); + ABORT("Unmarked tse"); + } + } + } + for (i = 0; i < TS_CACHE_SIZE; ++i) { + p = key -> cache[i]; + if (p != &invalid_tse && !GC_is_marked(GC_base(p))) { + GC_err_printf( + "Cached thread-specific-data entry at %p not marked\n",p); + ABORT("Unmarked cached tse"); + } + } +} + +#endif + +#endif /* USE_CUSTOM_SPECIFIC */ |