| 1 |
721 |
jeremybenn |
/*
|
| 2 |
|
|
* Copyright (c) 2000 by Hewlett-Packard Company. All rights reserved.
|
| 3 |
|
|
*
|
| 4 |
|
|
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
|
| 5 |
|
|
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
|
| 6 |
|
|
*
|
| 7 |
|
|
* Permission is hereby granted to use or copy this program
|
| 8 |
|
|
* for any purpose, provided the above notices are retained on all copies.
|
| 9 |
|
|
* Permission to modify the code and to distribute modified code is granted,
|
| 10 |
|
|
* provided the above notices are retained, and a notice that the code was
|
| 11 |
|
|
* modified is included with the above copyright notice.
|
| 12 |
|
|
*/
|
| 13 |
|
|
|
| 14 |
|
|
#include "private/gc_priv.h" /* For GC_compare_and_exchange, GC_memory_barrier */
|
| 15 |
|
|
|
| 16 |
|
|
#if defined(GC_LINUX_THREADS)
|
| 17 |
|
|
|
| 18 |
|
|
#include "private/specific.h"
|
| 19 |
|
|
|
| 20 |
|
|
static tse invalid_tse = {INVALID_QTID, 0, 0, INVALID_THREADID};
|
| 21 |
|
|
/* A thread-specific data entry which will never */
|
| 22 |
|
|
/* appear valid to a reader. Used to fill in empty */
|
| 23 |
|
|
/* cache entries to avoid a check for 0. */
|
| 24 |
|
|
|
| 25 |
|
|
int PREFIXED(key_create) (tsd ** key_ptr, void (* destructor)(void *)) {
|
| 26 |
|
|
int i;
|
| 27 |
|
|
tsd * result = (tsd *)MALLOC_CLEAR(sizeof (tsd));
|
| 28 |
|
|
|
| 29 |
|
|
/* A quick alignment check, since we need atomic stores */
|
| 30 |
|
|
GC_ASSERT((unsigned long)(&invalid_tse.next) % sizeof(tse *) == 0);
|
| 31 |
|
|
if (0 == result) return ENOMEM;
|
| 32 |
|
|
pthread_mutex_init(&(result -> lock), NULL);
|
| 33 |
|
|
for (i = 0; i < TS_CACHE_SIZE; ++i) {
|
| 34 |
|
|
result -> cache[i] = &invalid_tse;
|
| 35 |
|
|
}
|
| 36 |
|
|
# ifdef GC_ASSERTIONS
|
| 37 |
|
|
for (i = 0; i < TS_HASH_SIZE; ++i) {
|
| 38 |
|
|
GC_ASSERT(result -> hash[i] == 0);
|
| 39 |
|
|
}
|
| 40 |
|
|
# endif
|
| 41 |
|
|
*key_ptr = result;
|
| 42 |
|
|
return 0;
|
| 43 |
|
|
}
|
| 44 |
|
|
|
| 45 |
|
|
int PREFIXED(setspecific) (tsd * key, void * value) {
|
| 46 |
|
|
pthread_t self = pthread_self();
|
| 47 |
|
|
int hash_val = HASH(self);
|
| 48 |
|
|
volatile tse * entry = (volatile tse *)MALLOC_CLEAR(sizeof (tse));
|
| 49 |
|
|
|
| 50 |
|
|
GC_ASSERT(self != INVALID_THREADID);
|
| 51 |
|
|
if (0 == entry) return ENOMEM;
|
| 52 |
|
|
pthread_mutex_lock(&(key -> lock));
|
| 53 |
|
|
/* Could easily check for an existing entry here. */
|
| 54 |
|
|
entry -> next = key -> hash[hash_val];
|
| 55 |
|
|
entry -> thread = self;
|
| 56 |
|
|
entry -> value = value;
|
| 57 |
|
|
GC_ASSERT(entry -> qtid == INVALID_QTID);
|
| 58 |
|
|
/* There can only be one writer at a time, but this needs to be */
|
| 59 |
|
|
/* atomic with respect to concurrent readers. */
|
| 60 |
|
|
*(volatile tse **)(key -> hash + hash_val) = entry;
|
| 61 |
|
|
pthread_mutex_unlock(&(key -> lock));
|
| 62 |
|
|
return 0;
|
| 63 |
|
|
}
|
| 64 |
|
|
|
| 65 |
|
|
/* Remove thread-specific data for this thread. Should be called on */
|
| 66 |
|
|
/* thread exit. */
|
| 67 |
|
|
void PREFIXED(remove_specific) (tsd * key) {
|
| 68 |
|
|
pthread_t self = pthread_self();
|
| 69 |
|
|
unsigned hash_val = HASH(self);
|
| 70 |
|
|
tse *entry;
|
| 71 |
|
|
tse **link = key -> hash + hash_val;
|
| 72 |
|
|
|
| 73 |
|
|
pthread_mutex_lock(&(key -> lock));
|
| 74 |
|
|
entry = *link;
|
| 75 |
|
|
while (entry != NULL && entry -> thread != self) {
|
| 76 |
|
|
link = &(entry -> next);
|
| 77 |
|
|
entry = *link;
|
| 78 |
|
|
}
|
| 79 |
|
|
/* Invalidate qtid field, since qtids may be reused, and a later */
|
| 80 |
|
|
/* cache lookup could otherwise find this entry. */
|
| 81 |
|
|
entry -> qtid = INVALID_QTID;
|
| 82 |
|
|
if (entry != NULL) {
|
| 83 |
|
|
*link = entry -> next;
|
| 84 |
|
|
/* Atomic! concurrent accesses still work. */
|
| 85 |
|
|
/* They must, since readers don't lock. */
|
| 86 |
|
|
/* We shouldn't need a volatile access here, */
|
| 87 |
|
|
/* since both this and the preceding write */
|
| 88 |
|
|
/* should become visible no later than */
|
| 89 |
|
|
/* the pthread_mutex_unlock() call. */
|
| 90 |
|
|
}
|
| 91 |
|
|
/* If we wanted to deallocate the entry, we'd first have to clear */
|
| 92 |
|
|
/* any cache entries pointing to it. That probably requires */
|
| 93 |
|
|
/* additional synchronization, since we can't prevent a concurrent */
|
| 94 |
|
|
/* cache lookup, which should still be examining deallocated memory.*/
|
| 95 |
|
|
/* This can only happen if the concurrent access is from another */
|
| 96 |
|
|
/* thread, and hence has missed the cache, but still... */
|
| 97 |
|
|
|
| 98 |
|
|
/* With GC, we're done, since the pointers from the cache will */
|
| 99 |
|
|
/* be overwritten, all local pointers to the entries will be */
|
| 100 |
|
|
/* dropped, and the entry will then be reclaimed. */
|
| 101 |
|
|
pthread_mutex_unlock(&(key -> lock));
|
| 102 |
|
|
}
|
| 103 |
|
|
|
| 104 |
|
|
/* Note that even the slow path doesn't lock. */
|
| 105 |
|
|
void * PREFIXED(slow_getspecific) (tsd * key, unsigned long qtid,
|
| 106 |
|
|
tse * volatile * cache_ptr) {
|
| 107 |
|
|
pthread_t self = pthread_self();
|
| 108 |
|
|
unsigned hash_val = HASH(self);
|
| 109 |
|
|
tse *entry = key -> hash[hash_val];
|
| 110 |
|
|
|
| 111 |
|
|
GC_ASSERT(qtid != INVALID_QTID);
|
| 112 |
|
|
while (entry != NULL && entry -> thread != self) {
|
| 113 |
|
|
entry = entry -> next;
|
| 114 |
|
|
}
|
| 115 |
|
|
if (entry == NULL) return NULL;
|
| 116 |
|
|
/* Set cache_entry. */
|
| 117 |
|
|
entry -> qtid = qtid;
|
| 118 |
|
|
/* It's safe to do this asynchronously. Either value */
|
| 119 |
|
|
/* is safe, though may produce spurious misses. */
|
| 120 |
|
|
/* We're replacing one qtid with another one for the */
|
| 121 |
|
|
/* same thread. */
|
| 122 |
|
|
*cache_ptr = entry;
|
| 123 |
|
|
/* Again this is safe since pointer assignments are */
|
| 124 |
|
|
/* presumed atomic, and either pointer is valid. */
|
| 125 |
|
|
return entry -> value;
|
| 126 |
|
|
}
|
| 127 |
|
|
|
| 128 |
|
|
#endif /* GC_LINUX_THREADS */
|
