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-rw-r--r--include/private/specific.h24
1 files changed, 18 insertions, 6 deletions
diff --git a/include/private/specific.h b/include/private/specific.h
index 60c152c..399f84f 100644
--- a/include/private/specific.h
+++ b/include/private/specific.h
@@ -27,16 +27,22 @@
#define TS_HASH_SIZE 1024
#define HASH(n) (((((long)n) >> 8) ^ (long)n) & (TS_HASH_SIZE - 1))
+/* An entry describing a thread-specific value for a given thread. */
+/* All such accessible structures preserve the invariant that if either */
+/* thread is a valid pthread id or qtid is a valid "quick tread id" */
+/* for a thread, then value holds the corresponding thread specific */
+/* value. This invariant must be preserved at ALL times, since */
+/* asynchronous reads are allowed. */
typedef struct thread_specific_entry {
unsigned long qtid; /* quick thread id, only for cache */
void * value;
- pthread_t thread;
struct thread_specific_entry *next;
+ pthread_t thread;
} tse;
/* We represent each thread-specific datum as two tables. The first is */
-/* a cache, index by a "quick thread identifier". The "quick" thread */
+/* a cache, indexed by a "quick thread identifier". The "quick" thread */
/* identifier is an easy to compute value, which is guaranteed to */
/* determine the thread, though a thread may correspond to more than */
/* one value. We typically use the address of a page in the stack. */
@@ -45,12 +51,15 @@ typedef struct thread_specific_entry {
/* Return the "quick thread id". Default version. Assumes page size, */
/* or at least thread stack separation, is at least 4K. */
-static __inline__ long quick_thread_id() {
+/* Must be defined so that it never returns 0. (Page 0 can't really */
+/* be part of any stack, since that would make 0 a valid stack pointer.)*/
+static __inline__ unsigned long quick_thread_id() {
int dummy;
- return (long)(&dummy) >> 12;
+ return (unsigned long)(&dummy) >> 12;
}
-#define INVALID_QTID ((unsigned long)(-1))
+#define INVALID_QTID ((unsigned long)0)
+#define INVALID_THREADID ((pthread_t)0)
typedef struct thread_specific_data {
tse * volatile cache[TS_CACHE_SIZE];
@@ -76,7 +85,10 @@ static __inline__ void * PREFIXED(getspecific) (tsd * key) {
unsigned hash_val = CACHE_HASH(qtid);
tse * volatile * entry_ptr = key -> cache + hash_val;
tse * entry = *entry_ptr; /* Must be loaded only once. */
- if (entry -> qtid == qtid) return entry -> value;
+ if (entry -> qtid == qtid) {
+ GC_ASSERT(entry -> thread == pthread_self());
+ return entry -> value;
+ }
return PREFIXED(slow_getspecific) (key, qtid, entry_ptr);
}