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Diffstat (limited to 'linuxthreads/spinlock.h')
| -rw-r--r-- | linuxthreads/spinlock.h | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/linuxthreads/spinlock.h b/linuxthreads/spinlock.h new file mode 100644 index 0000000000..ff96fc3360 --- /dev/null +++ b/linuxthreads/spinlock.h @@ -0,0 +1,218 @@ +/* Linuxthreads - a simple clone()-based implementation of Posix */ +/* threads for Linux. */ +/* Copyright (C) 1998 Xavier Leroy (Xavier.Leroy@inria.fr) */ +/* */ +/* This program is free software; you can redistribute it and/or */ +/* modify it under the terms of the GNU Library General Public License */ +/* as published by the Free Software Foundation; either version 2 */ +/* of the License, or (at your option) any later version. */ +/* */ +/* This program is distributed in the hope that it will be useful, */ +/* but WITHOUT ANY WARRANTY; without even the implied warranty of */ +/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */ +/* GNU Library General Public License for more details. */ + +#include <bits/initspin.h> + + +/* 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; +extern int __pthread_compare_and_swap(long * ptr, long oldval, long newval, + int * spinlock); + +static inline int compare_and_swap(long * ptr, long oldval, long newval, + int * spinlock) +{ + if (__builtin_expect (__pthread_has_cas, 1)) + return __compare_and_swap(ptr, oldval, newval); + else + return __pthread_compare_and_swap(ptr, oldval, newval, spinlock); +} + +#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) +{ + return __compare_and_swap(ptr, oldval, newval); +} + +#else + +extern int __pthread_compare_and_swap(long * ptr, long oldval, long newval, + int * spinlock); + +static inline int compare_and_swap(long * ptr, long oldval, long newval, + int * spinlock) +{ + return __pthread_compare_and_swap(ptr, oldval, newval, spinlock); +} + +#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 int __pthread_unlock(struct _pthread_fastlock *lock); + +static inline void __pthread_init_lock(struct _pthread_fastlock * lock) +{ + lock->__status = 0; + lock->__spinlock = __LT_SPINLOCK_INIT; +} + +static inline int __pthread_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 + { + return (testandset(&lock->__spinlock) ? EBUSY : 0); + } +#endif + +#if defined HAS_COMPARE_AND_SWAP + do { + 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; +} + +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 */ + +static inline long atomic_increment(struct pthread_atomic *pa) +{ + long oldval; + + do { + oldval = pa->p_count; + } while (!compare_and_swap(&pa->p_count, oldval, oldval + 1, &pa->p_spinlock)); + + return oldval; +} + + +static inline long atomic_decrement(struct pthread_atomic *pa) +{ + long oldval; + + do { + oldval = pa->p_count; + } while (!compare_and_swap(&pa->p_count, oldval, oldval - 1, &pa->p_spinlock)); + + return oldval; +} + + +static inline __attribute__((always_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)); + } +} |