1d2fc9b3c5
2000-01-03 Kaz Kylheku <kaz@ashi.footprints.net>
Redesigned how cancellation unblocks a thread from internal
cancellation points (sem_wait, pthread_join,
pthread_cond_{wait,timedwait}).
Cancellation won't eat a signal in any of these functions
(*required* by POSIX and Single Unix Spec!).
* condvar.c: spontaneous wakeup on pthread_cond_timedwait won't eat a
simultaneous condition variable signal (not required by POSIX
or Single Unix Spec, but nice).
* spinlock.c: __pthread_lock queues back any received restarts
that don't belong to it instead of assuming ownership of lock
upon any restart; fastlock can no longer be acquired by two threads
simultaneously.
* restart.h: restarts queue even on kernels that don't have
queued real time signals (2.0, early 2.1), thanks to atomic counter,
avoiding a rare race condition in pthread_cond_timedwait.
103 lines
3.1 KiB
C
103 lines
3.1 KiB
C
/* Linuxthreads - a simple clone()-based implementation of Posix */
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/* threads for Linux. */
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/* Copyright (C) 1998 Xavier Leroy (Xavier.Leroy@inria.fr) */
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/* */
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/* This program is free software; you can redistribute it and/or */
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/* modify it under the terms of the GNU Library General Public License */
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/* as published by the Free Software Foundation; either version 2 */
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/* of the License, or (at your option) any later version. */
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/* */
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/* This program is distributed in the hope that it will be useful, */
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/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
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/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
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/* GNU Library General Public License for more details. */
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#if defined(TEST_FOR_COMPARE_AND_SWAP)
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extern int __pthread_has_cas;
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extern int __pthread_compare_and_swap(long * ptr, long oldval, long newval,
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int * spinlock);
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static inline int compare_and_swap(long * ptr, long oldval, long newval,
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int * spinlock)
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{
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if (__builtin_expect (__pthread_has_cas, 1))
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return __compare_and_swap(ptr, oldval, newval);
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else
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return __pthread_compare_and_swap(ptr, oldval, newval, spinlock);
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}
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#elif defined(HAS_COMPARE_AND_SWAP)
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static inline int compare_and_swap(long * ptr, long oldval, long newval,
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int * spinlock)
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{
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return __compare_and_swap(ptr, oldval, newval);
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}
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#else
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extern int __pthread_compare_and_swap(long * ptr, long oldval, long newval,
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int * spinlock);
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static inline int compare_and_swap(long * ptr, long oldval, long newval,
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int * spinlock)
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{
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return __pthread_compare_and_swap(ptr, oldval, newval, spinlock);
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}
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#endif
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/* Internal locks */
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extern void internal_function __pthread_lock(struct _pthread_fastlock * lock,
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pthread_descr self);
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extern void internal_function __pthread_unlock(struct _pthread_fastlock *lock);
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static inline void __pthread_init_lock(struct _pthread_fastlock * lock)
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{
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lock->__status = 0;
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lock->__spinlock = 0;
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}
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static inline int __pthread_trylock (struct _pthread_fastlock * lock)
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{
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long oldstatus;
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do {
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oldstatus = lock->__status;
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if (oldstatus != 0) return EBUSY;
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} while(! compare_and_swap(&lock->__status, 0, 1, &lock->__spinlock));
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return 0;
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}
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#define LOCK_INITIALIZER {0, 0}
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/* Operations on pthread_atomic, which is defined in internals.h */
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static inline long atomic_increment(struct pthread_atomic *pa)
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{
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long oldval;
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do {
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oldval = pa->p_count;
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} while (!compare_and_swap(&pa->p_count, oldval, oldval + 1, &pa->p_spinlock));
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return oldval;
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}
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static inline long atomic_decrement(struct pthread_atomic *pa)
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{
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long oldval;
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do {
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oldval = pa->p_count;
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} while (!compare_and_swap(&pa->p_count, oldval, oldval - 1, &pa->p_spinlock));
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return oldval;
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}
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#define ATOMIC_INITIALIZER { 0, 0 }
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