gc6.0 tarball importgc6_0

1 files changed, 108 insertions, 0 deletions

diff --git a/specific.c b/specific.c
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+++ b/specific.c
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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.
+ */
+
+#if defined(LINUX_THREADS) || defined(GC_LINUX_THREADS)
+
+#include "private/gc_priv.h" /* For GC_compare_and_exchange, GC_memory_barrier */
+#include "private/specific.h"
+
+static tse invalid_tse; 	/* 0 qtid is guaranteed to be invalid	*/
+
+int PREFIXED(key_create) (tsd ** key_ptr, void (* destructor)(void *)) {
+    int i;
+    tsd * result = (tsd *)MALLOC_CLEAR(sizeof (tsd));
+
+    if (0 == result) return ENOMEM;
+    pthread_mutex_init(&(result -> lock), NULL);
+    for (i = 0; i < TS_CACHE_SIZE; ++i) {
+	result -> cache[i] = &invalid_tse;
+    }
+    *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));
+    
+    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;
+    /* 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.		*/
+    }
+    /* 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];
+
+    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.		*/
+	*cache_ptr = entry;
+		/* Again this is safe since pointer assignments are 	*/
+		/* presumed atomic, and either pointer is valid.	*/
+    return entry -> value;
+}
+
+#endif /* LINUX_THREADS */