--- /dev/null
+/*
+ * 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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