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Diffstat (limited to 'libpthread/linuxthreads/rwlock.c')
| -rw-r--r-- | libpthread/linuxthreads/rwlock.c | 486 |
1 files changed, 0 insertions, 486 deletions
diff --git a/libpthread/linuxthreads/rwlock.c b/libpthread/linuxthreads/rwlock.c deleted file mode 100644 index 977fd88af..000000000 --- a/libpthread/linuxthreads/rwlock.c +++ /dev/null @@ -1,486 +0,0 @@ -/* Read-write lock implementation. - Copyright (C) 1998 Free Software Foundation, Inc. - This file is part of the GNU C Library. - Contributed by Xavier Leroy <Xavier.Leroy@inria.fr> - and Ulrich Drepper <drepper@cygnus.com>, 1998. - - The GNU C Library 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. - - The GNU C Library 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. - - You should have received a copy of the GNU Library General Public - License along with the GNU C Library; see the file COPYING.LIB. If not, - write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, - Boston, MA 02111-1307, USA. */ - -#include <errno.h> -#include <pthread.h> -#include <stdlib.h> -#include "internals.h" -#include "queue.h" -#include "spinlock.h" -#include "restart.h" - -/* - * Check whether the calling thread already owns one or more read locks on the - * specified lock. If so, return a pointer to the read lock info structure - * corresponding to that lock. - */ - -static pthread_readlock_info * -rwlock_is_in_list(pthread_descr self, pthread_rwlock_t *rwlock) -{ - pthread_readlock_info *info; - - for (info = self->p_readlock_list; info != NULL; info = info->pr_next) - { - if (info->pr_lock == rwlock) - return info; - } - - return NULL; -} - -/* - * Add a new lock to the thread's list of locks for which it has a read lock. - * A new info node must be allocated for this, which is taken from the thread's - * free list, or by calling malloc. If malloc fails, a null pointer is - * returned. Otherwise the lock info structure is initialized and pushed - * onto the thread's list. - */ - -static pthread_readlock_info * -rwlock_add_to_list(pthread_descr self, pthread_rwlock_t *rwlock) -{ - pthread_readlock_info *info = self->p_readlock_free; - - if (info != NULL) - self->p_readlock_free = info->pr_next; - else - info = malloc(sizeof *info); - - if (info == NULL) - return NULL; - - info->pr_lock_count = 1; - info->pr_lock = rwlock; - info->pr_next = self->p_readlock_list; - self->p_readlock_list = info; - - return info; -} - -/* - * If the thread owns a read lock over the given pthread_rwlock_t, - * and this read lock is tracked in the thread's lock list, - * this function returns a pointer to the info node in that list. - * It also decrements the lock count within that node, and if - * it reaches zero, it removes the node from the list. - * If nothing is found, it returns a null pointer. - */ - -static pthread_readlock_info * -rwlock_remove_from_list(pthread_descr self, pthread_rwlock_t *rwlock) -{ - pthread_readlock_info **pinfo; - - for (pinfo = &self->p_readlock_list; *pinfo != NULL; pinfo = &(*pinfo)->pr_next) - { - if ((*pinfo)->pr_lock == rwlock) - { - pthread_readlock_info *info = *pinfo; - if (--info->pr_lock_count == 0) - *pinfo = info->pr_next; - return info; - } - } - - return NULL; -} - -/* - * This function checks whether the conditions are right to place a read lock. - * It returns 1 if so, otherwise zero. The rwlock's internal lock must be - * locked upon entry. - */ - -static int -rwlock_can_rdlock(pthread_rwlock_t *rwlock, int have_lock_already) -{ - /* Can't readlock; it is write locked. */ - if (rwlock->__rw_writer != NULL) - return 0; - - /* Lock prefers readers; get it. */ - if (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_READER_NP) - return 1; - - /* Lock prefers writers, but none are waiting. */ - if (queue_is_empty(&rwlock->__rw_write_waiting)) - return 1; - - /* Writers are waiting, but this thread already has a read lock */ - if (have_lock_already) - return 1; - - /* Writers are waiting, and this is a new lock */ - return 0; -} - -/* - * This function helps support brain-damaged recursive read locking - * semantics required by Unix 98, while maintaining write priority. - * This basically determines whether this thread already holds a read lock - * already. It returns 1 if so, otherwise it returns 0. - * - * If the thread has any ``untracked read locks'' then it just assumes - * that this lock is among them, just to be safe, and returns 1. - * - * Also, if it finds the thread's lock in the list, it sets the pointer - * referenced by pexisting to refer to the list entry. - * - * If the thread has no untracked locks, and the lock is not found - * in its list, then it is added to the list. If this fails, - * then *pout_of_mem is set to 1. - */ - -static int -rwlock_have_already(pthread_descr *pself, pthread_rwlock_t *rwlock, - pthread_readlock_info **pexisting, int *pout_of_mem) -{ - pthread_readlock_info *existing = NULL; - int out_of_mem = 0, have_lock_already = 0; - pthread_descr self = *pself; - - if (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_WRITER_NP) - { - if (!self) - self = thread_self(); - - existing = rwlock_is_in_list(self, rwlock); - - if (existing != NULL || self->p_untracked_readlock_count > 0) - have_lock_already = 1; - else - { - existing = rwlock_add_to_list(self, rwlock); - if (existing == NULL) - out_of_mem = 1; - } - } - - *pout_of_mem = out_of_mem; - *pexisting = existing; - *pself = self; - - return have_lock_already; -} - -int -pthread_rwlock_init (pthread_rwlock_t *rwlock, - const pthread_rwlockattr_t *attr) -{ - __pthread_init_lock(&rwlock->__rw_lock); - rwlock->__rw_readers = 0; - rwlock->__rw_writer = NULL; - rwlock->__rw_read_waiting = NULL; - rwlock->__rw_write_waiting = NULL; - - if (attr == NULL) - { - rwlock->__rw_kind = PTHREAD_RWLOCK_DEFAULT_NP; - rwlock->__rw_pshared = PTHREAD_PROCESS_PRIVATE; - } - else - { - rwlock->__rw_kind = attr->__lockkind; - rwlock->__rw_pshared = attr->__pshared; - } - - return 0; -} - - -int -pthread_rwlock_destroy (pthread_rwlock_t *rwlock) -{ - int readers; - _pthread_descr writer; - - __pthread_lock (&rwlock->__rw_lock, NULL); - readers = rwlock->__rw_readers; - writer = rwlock->__rw_writer; - __pthread_unlock (&rwlock->__rw_lock); - - if (readers > 0 || writer != NULL) - return EBUSY; - - return 0; -} - -int -pthread_rwlock_rdlock (pthread_rwlock_t *rwlock) -{ - pthread_descr self = NULL; - pthread_readlock_info *existing; - int out_of_mem, have_lock_already; - - have_lock_already = rwlock_have_already(&self, rwlock, - &existing, &out_of_mem); - - for (;;) - { - if (self == NULL) - self = thread_self (); - - __pthread_lock (&rwlock->__rw_lock, self); - - if (rwlock_can_rdlock(rwlock, have_lock_already)) - break; - - enqueue (&rwlock->__rw_read_waiting, self); - __pthread_unlock (&rwlock->__rw_lock); - suspend (self); /* This is not a cancellation point */ - } - - ++rwlock->__rw_readers; - __pthread_unlock (&rwlock->__rw_lock); - - if (have_lock_already || out_of_mem) - { - if (existing != NULL) - existing->pr_lock_count++; - else - self->p_untracked_readlock_count++; - } - - return 0; -} - -int -pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock) -{ - pthread_descr self = thread_self(); - pthread_readlock_info *existing; - int out_of_mem, have_lock_already; - int retval = EBUSY; - - have_lock_already = rwlock_have_already(&self, rwlock, - &existing, &out_of_mem); - - __pthread_lock (&rwlock->__rw_lock, self); - - /* 0 is passed to here instead of have_lock_already. - This is to meet Single Unix Spec requirements: - if writers are waiting, pthread_rwlock_tryrdlock - does not acquire a read lock, even if the caller has - one or more read locks already. */ - - if (rwlock_can_rdlock(rwlock, 0)) - { - ++rwlock->__rw_readers; - retval = 0; - } - - __pthread_unlock (&rwlock->__rw_lock); - - if (retval == 0) - { - if (have_lock_already || out_of_mem) - { - if (existing != NULL) - existing->pr_lock_count++; - else - self->p_untracked_readlock_count++; - } - } - - return retval; -} - - -int -pthread_rwlock_wrlock (pthread_rwlock_t *rwlock) -{ - pthread_descr self = thread_self (); - - while(1) - { - __pthread_lock (&rwlock->__rw_lock, self); - if (rwlock->__rw_readers == 0 && rwlock->__rw_writer == NULL) - { - rwlock->__rw_writer = self; - __pthread_unlock (&rwlock->__rw_lock); - return 0; - } - - /* Suspend ourselves, then try again */ - enqueue (&rwlock->__rw_write_waiting, self); - __pthread_unlock (&rwlock->__rw_lock); - suspend (self); /* This is not a cancellation point */ - } -} - - -int -pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock) -{ - int result = EBUSY; - - __pthread_lock (&rwlock->__rw_lock, NULL); - if (rwlock->__rw_readers == 0 && rwlock->__rw_writer == NULL) - { - rwlock->__rw_writer = thread_self (); - result = 0; - } - __pthread_unlock (&rwlock->__rw_lock); - - return result; -} - - -int -pthread_rwlock_unlock (pthread_rwlock_t *rwlock) -{ - pthread_descr torestart; - pthread_descr th; - - __pthread_lock (&rwlock->__rw_lock, NULL); - if (rwlock->__rw_writer != NULL) - { - /* Unlocking a write lock. */ - if (rwlock->__rw_writer != thread_self ()) - { - __pthread_unlock (&rwlock->__rw_lock); - return EPERM; - } - rwlock->__rw_writer = NULL; - - if (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_READER_NP - || (th = dequeue (&rwlock->__rw_write_waiting)) == NULL) - { - /* Restart all waiting readers. */ - torestart = rwlock->__rw_read_waiting; - rwlock->__rw_read_waiting = NULL; - __pthread_unlock (&rwlock->__rw_lock); - while ((th = dequeue (&torestart)) != NULL) - restart (th); - } - else - { - /* Restart one waiting writer. */ - __pthread_unlock (&rwlock->__rw_lock); - restart (th); - } - } - else - { - /* Unlocking a read lock. */ - if (rwlock->__rw_readers == 0) - { - __pthread_unlock (&rwlock->__rw_lock); - return EPERM; - } - - --rwlock->__rw_readers; - if (rwlock->__rw_readers == 0) - /* Restart one waiting writer, if any. */ - th = dequeue (&rwlock->__rw_write_waiting); - else - th = NULL; - - __pthread_unlock (&rwlock->__rw_lock); - if (th != NULL) - restart (th); - - /* Recursive lock fixup */ - - if (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_WRITER_NP) - { - pthread_descr self = thread_self(); - pthread_readlock_info *victim = rwlock_remove_from_list(self, rwlock); - - if (victim != NULL) - { - if (victim->pr_lock_count == 0) - { - victim->pr_next = self->p_readlock_free; - self->p_readlock_free = victim; - } - } - else - { - if (self->p_untracked_readlock_count > 0) - self->p_untracked_readlock_count--; - } - } - } - - return 0; -} - - - -int -pthread_rwlockattr_init (pthread_rwlockattr_t *attr) -{ - attr->__lockkind = 0; - attr->__pshared = 0; - - return 0; -} - - -int -pthread_rwlockattr_destroy (pthread_rwlockattr_t *attr) -{ - return 0; -} - - -int -pthread_rwlockattr_getpshared (const pthread_rwlockattr_t *attr, int *pshared) -{ - *pshared = attr->__pshared; - return 0; -} - - -int -pthread_rwlockattr_setpshared (pthread_rwlockattr_t *attr, int pshared) -{ - if (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED) - return EINVAL; - - attr->__pshared = pshared; - - return 0; -} - - -int -pthread_rwlockattr_getkind_np (const pthread_rwlockattr_t *attr, int *pref) -{ - *pref = attr->__lockkind; - return 0; -} - - -int -pthread_rwlockattr_setkind_np (pthread_rwlockattr_t *attr, int pref) -{ - if (pref != PTHREAD_RWLOCK_PREFER_READER_NP - && pref != PTHREAD_RWLOCK_PREFER_WRITER_NP - && pref != PTHREAD_RWLOCK_DEFAULT_NP) - return EINVAL; - - attr->__lockkind = pref; - - return 0; -} |