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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [boehm-gc/] [specific.c] - Rev 729
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/* * 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 GC_compare_and_exchange, GC_memory_barrier */ #if defined(GC_LINUX_THREADS) #include "private/specific.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. */ *(volatile tse **)(key -> hash + hash_val) = 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; } #endif /* GC_LINUX_THREADS */
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