diff options
Diffstat (limited to 'gcc-4.2.1/boehm-gc/include/private/specific.h')
| -rw-r--r-- | gcc-4.2.1/boehm-gc/include/private/specific.h | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/gcc-4.2.1/boehm-gc/include/private/specific.h b/gcc-4.2.1/boehm-gc/include/private/specific.h new file mode 100644 index 000000000..d04e19f5a --- /dev/null +++ b/gcc-4.2.1/boehm-gc/include/private/specific.h @@ -0,0 +1,95 @@ +/* + * This is a reimplementation of a subset of the pthread_getspecific/setspecific + * interface. This appears to outperform the standard linuxthreads one + * by a significant margin. + * The major restriction is that each thread may only make a single + * pthread_setspecific call on a single key. (The current data structure + * doesn't really require that. The restriction should be easily removable.) + * We don't currently support the destruction functions, though that + * could be done. + * We also currently assume that only one pthread_setspecific call + * can be executed at a time, though that assumption would be easy to remove + * by adding a lock. + */ + +#include <errno.h> + +/* Called during key creation or setspecific. */ +/* For the GC we already hold lock. */ +/* Currently allocated objects leak on thread exit. */ +/* That's hard to fix, but OK if we allocate garbage */ +/* collected memory. */ +#define MALLOC_CLEAR(n) GC_INTERNAL_MALLOC(n, NORMAL) +#define PREFIXED(name) GC_##name + +#define TS_CACHE_SIZE 1024 +#define CACHE_HASH(n) (((((long)n) >> 8) ^ (long)n) & (TS_CACHE_SIZE - 1)) +#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; + struct thread_specific_entry *next; + pthread_t thread; +} tse; + + +/* We represent each thread-specific datum as two tables. The first is */ +/* 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. */ +/* The second is a hash table, indexed by pthread_self(). It is used */ +/* only as a backup. */ + +/* Return the "quick thread id". Default version. Assumes page size, */ +/* or at least thread stack separation, is at least 4K. */ +/* 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 (unsigned long)(&dummy) >> 12; +} + +#define INVALID_QTID ((unsigned long)0) +#define INVALID_THREADID ((pthread_t)0) + +typedef struct thread_specific_data { + tse * volatile cache[TS_CACHE_SIZE]; + /* A faster index to the hash table */ + tse * hash[TS_HASH_SIZE]; + pthread_mutex_t lock; +} tsd; + +typedef tsd * PREFIXED(key_t); + +extern int PREFIXED(key_create) (tsd ** key_ptr, void (* destructor)(void *)); + +extern int PREFIXED(setspecific) (tsd * key, void * value); + +extern void PREFIXED(remove_specific) (tsd * key); + +/* An internal version of getspecific that assumes a cache miss. */ +void * PREFIXED(slow_getspecific) (tsd * key, unsigned long qtid, + tse * volatile * cache_entry); + +static __inline__ void * PREFIXED(getspecific) (tsd * key) { + long qtid = quick_thread_id(); + unsigned hash_val = CACHE_HASH(qtid); + tse * volatile * entry_ptr = key -> cache + hash_val; + tse * entry = *entry_ptr; /* Must be loaded only once. */ + if (EXPECT(entry -> qtid == qtid, 1)) { + GC_ASSERT(entry -> thread == pthread_self()); + return entry -> value; + } + return PREFIXED(slow_getspecific) (key, qtid, entry_ptr); +} + + |