summaryrefslogtreecommitdiff
path: root/libpthread/linuxthreads.old/rwlock.c
diff options
context:
space:
mode:
Diffstat (limited to 'libpthread/linuxthreads.old/rwlock.c')
-rw-r--r--libpthread/linuxthreads.old/rwlock.c485
1 files changed, 0 insertions, 485 deletions
diff --git a/libpthread/linuxthreads.old/rwlock.c b/libpthread/linuxthreads.old/rwlock.c
deleted file mode 100644
index 3ab940261..000000000
--- a/libpthread/linuxthreads.old/rwlock.c
+++ /dev/null
@@ -1,485 +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,
- see <http://www.gnu.org/licenses/>. */
-
-#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 attribute_unused)
-{
- 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;
-}
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-25 13:49:44 +0000