From 187dd78d7bd1c03fcf16e54a30314512d38e1a4a Mon Sep 17 00:00:00 2001 From: Eric Andersen Date: Thu, 27 Feb 2003 18:13:05 +0000 Subject: Major update for pthreads, based in large part on improvements from glibc 2.3. This should make threads much more efficient. -Erik --- libpthread/linuxthreads/spinlock.h | 132 ++++++++++++++++++++++++++++++++++--- 1 file changed, 124 insertions(+), 8 deletions(-) (limited to 'libpthread/linuxthreads/spinlock.h') diff --git a/libpthread/linuxthreads/spinlock.h b/libpthread/linuxthreads/spinlock.h index aae18a27b..0ec40c57c 100644 --- a/libpthread/linuxthreads/spinlock.h +++ b/libpthread/linuxthreads/spinlock.h @@ -12,6 +12,27 @@ /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */ /* GNU Library General Public License for more details. */ +#include + + +/* There are 2 compare and swap synchronization primitives with + different semantics: + + 1. compare_and_swap, which has acquire semantics (i.e. it + completes befor subsequent writes.) + 2. compare_and_swap_with_release_semantics, which has release + semantics (it completes after previous writes.) + + For those platforms on which they are the same. HAS_COMPARE_AND_SWAP + should be defined. For those platforms on which they are different, + HAS_COMPARE_AND_SWAP_WITH_RELEASE_SEMANTICS has to be defined. */ + +#ifndef HAS_COMPARE_AND_SWAP +#ifdef HAS_COMPARE_AND_SWAP_WITH_RELEASE_SEMANTICS +#define HAS_COMPARE_AND_SWAP +#endif +#endif + #if defined(TEST_FOR_COMPARE_AND_SWAP) extern int __pthread_has_cas; @@ -29,6 +50,22 @@ static inline int compare_and_swap(long * ptr, long oldval, long newval, #elif defined(HAS_COMPARE_AND_SWAP) +#ifdef IMPLEMENT_TAS_WITH_CAS +#define testandset(p) !__compare_and_swap((long int *) p, 0, 1) +#endif + +#ifdef HAS_COMPARE_AND_SWAP_WITH_RELEASE_SEMANTICS + +static inline int +compare_and_swap_with_release_semantics (long * ptr, long oldval, + long newval, int * spinlock) +{ + return __compare_and_swap_with_release_semantics (ptr, oldval, + newval); +} + +#endif + static inline int compare_and_swap(long * ptr, long oldval, long newval, int * spinlock) { @@ -48,30 +85,90 @@ static inline int compare_and_swap(long * ptr, long oldval, long newval, #endif +#ifndef HAS_COMPARE_AND_SWAP_WITH_RELEASE_SEMANTICS +#define compare_and_swap_with_release_semantics compare_and_swap +#define __compare_and_swap_with_release_semantics __compare_and_swap +#endif + /* Internal locks */ extern void internal_function __pthread_lock(struct _pthread_fastlock * lock, pthread_descr self); -extern void internal_function __pthread_unlock(struct _pthread_fastlock *lock); +extern int __pthread_unlock(struct _pthread_fastlock *lock); static inline void __pthread_init_lock(struct _pthread_fastlock * lock) { lock->__status = 0; - lock->__spinlock = 0; + lock->__spinlock = __LT_SPINLOCK_INIT; } static inline int __pthread_trylock (struct _pthread_fastlock * lock) { - long oldstatus; +#if defined TEST_FOR_COMPARE_AND_SWAP + if (!__pthread_has_cas) +#endif +#if !defined HAS_COMPARE_AND_SWAP || defined TEST_FOR_COMPARE_AND_SWAP + { + return (testandset(&lock->__spinlock) ? EBUSY : 0); + } +#endif +#if defined HAS_COMPARE_AND_SWAP do { - oldstatus = lock->__status; - if (oldstatus != 0) return EBUSY; - } while(! compare_and_swap(&lock->__status, 0, 1, &lock->__spinlock)); + if (lock->__status != 0) return EBUSY; + } while(! __compare_and_swap(&lock->__status, 0, 1)); return 0; +#endif +} + +/* Variation of internal lock used for pthread_mutex_t, supporting + timed-out waits. Warning: do not mix these operations with the above ones + over the same lock object! */ + +extern void __pthread_alt_lock(struct _pthread_fastlock * lock, + pthread_descr self); + +extern int __pthread_alt_timedlock(struct _pthread_fastlock * lock, + pthread_descr self, const struct timespec *abstime); + +extern void __pthread_alt_unlock(struct _pthread_fastlock *lock); + +static inline void __pthread_alt_init_lock(struct _pthread_fastlock * lock) +{ + lock->__status = 0; + lock->__spinlock = __LT_SPINLOCK_INIT; } -#define LOCK_INITIALIZER {0, 0} +static inline int __pthread_alt_trylock (struct _pthread_fastlock * lock) +{ +#if defined TEST_FOR_COMPARE_AND_SWAP + if (!__pthread_has_cas) +#endif +#if !defined HAS_COMPARE_AND_SWAP || defined TEST_FOR_COMPARE_AND_SWAP + { + int res = EBUSY; + + if (testandset(&lock->__spinlock) == 0) + { + if (lock->__status == 0) + { + lock->__status = 1; + WRITE_MEMORY_BARRIER(); + res = 0; + } + lock->__spinlock = __LT_SPINLOCK_INIT; + } + return res; + } +#endif + +#if defined HAS_COMPARE_AND_SWAP + do { + if (lock->__status != 0) return EBUSY; + } while(! compare_and_swap(&lock->__status, 0, 1, &lock->__spinlock)); + return 0; +#endif +} /* Operations on pthread_atomic, which is defined in internals.h */ @@ -98,5 +195,24 @@ static inline long atomic_decrement(struct pthread_atomic *pa) return oldval; } -#define ATOMIC_INITIALIZER { 0, 0 } +static inline void +__pthread_set_own_extricate_if (pthread_descr self, pthread_extricate_if *peif) +{ + /* Only store a non-null peif if the thread has cancellation enabled. + Otherwise pthread_cancel will unconditionally call the extricate handler, + and restart the thread giving rise to forbidden spurious wakeups. */ + if (peif == NULL + || THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) + { + /* If we are removing the extricate interface, we need to synchronize + against pthread_cancel so that it does not continue with a pointer + to a deallocated pthread_extricate_if struct! The thread lock + is (ab)used for this synchronization purpose. */ + if (peif == NULL) + __pthread_lock (THREAD_GETMEM(self, p_lock), self); + THREAD_SETMEM(self, p_extricate, peif); + if (peif == NULL) + __pthread_unlock (THREAD_GETMEM(self, p_lock)); + } +} -- cgit v1.2.3