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-rw-r--r--linuxthreads/rwlock.c658
1 files changed, 658 insertions, 0 deletions
diff --git a/linuxthreads/rwlock.c b/linuxthreads/rwlock.c
new file mode 100644
index 0000000000..f565f18706
--- /dev/null
+++ b/linuxthreads/rwlock.c
@@ -0,0 +1,658 @@
+/* Read-write lock implementation.
+ Copyright (C) 1998, 2000 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 Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser 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 <bits/libc-lock.h>
+#include <errno.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include "internals.h"
+#include "queue.h"
+#include "spinlock.h"
+#include "restart.h"
+
+/* Function called by pthread_cancel to remove the thread from
+ waiting inside pthread_rwlock_timedrdlock or pthread_rwlock_timedwrlock. */
+
+static int rwlock_rd_extricate_func(void *obj, pthread_descr th)
+{
+ pthread_rwlock_t *rwlock = obj;
+ int did_remove = 0;
+
+ __pthread_lock(&rwlock->__rw_lock, NULL);
+ did_remove = remove_from_queue(&rwlock->__rw_read_waiting, th);
+ __pthread_unlock(&rwlock->__rw_lock);
+
+ return did_remove;
+}
+
+static int rwlock_wr_extricate_func(void *obj, pthread_descr th)
+{
+ pthread_rwlock_t *rwlock = obj;
+ int did_remove = 0;
+
+ __pthread_lock(&rwlock->__rw_lock, NULL);
+ did_remove = remove_from_queue(&rwlock->__rw_write_waiting, th);
+ __pthread_unlock(&rwlock->__rw_lock);
+
+ return did_remove;
+}
+
+/*
+ * 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 = THREAD_GETMEM (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 = THREAD_GETMEM (self, p_readlock_free);
+
+ if (info != NULL)
+ THREAD_SETMEM (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 = THREAD_GETMEM (self, p_readlock_list);
+ THREAD_SETMEM (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)
+ *pself = self = thread_self();
+
+ existing = rwlock_is_in_list(self, rwlock);
+
+ if (existing != NULL
+ || THREAD_GETMEM (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;
+
+ 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;
+}
+strong_alias (__pthread_rwlock_init, pthread_rwlock_init)
+
+
+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;
+}
+strong_alias (__pthread_rwlock_destroy, pthread_rwlock_destroy)
+
+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);
+
+ if (self == NULL)
+ self = thread_self ();
+
+ for (;;)
+ {
+ __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;
+}
+strong_alias (__pthread_rwlock_rdlock, pthread_rwlock_rdlock)
+
+int
+__pthread_rwlock_timedrdlock (pthread_rwlock_t *rwlock,
+ const struct timespec *abstime)
+{
+ pthread_descr self = NULL;
+ pthread_readlock_info *existing;
+ int out_of_mem, have_lock_already;
+ pthread_extricate_if extr;
+
+ if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
+ return EINVAL;
+
+ have_lock_already = rwlock_have_already(&self, rwlock,
+ &existing, &out_of_mem);
+
+ if (self == NULL)
+ self = thread_self ();
+
+ /* Set up extrication interface */
+ extr.pu_object = rwlock;
+ extr.pu_extricate_func = rwlock_rd_extricate_func;
+
+ /* Register extrication interface */
+ __pthread_set_own_extricate_if (self, &extr);
+
+ for (;;)
+ {
+ __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);
+ /* This is not a cancellation point */
+ if (timedsuspend (self, abstime) == 0)
+ {
+ int was_on_queue;
+
+ __pthread_lock (&rwlock->__rw_lock, self);
+ was_on_queue = remove_from_queue (&rwlock->__rw_read_waiting, self);
+ __pthread_unlock (&rwlock->__rw_lock);
+
+ if (was_on_queue)
+ {
+ __pthread_set_own_extricate_if (self, 0);
+ return ETIMEDOUT;
+ }
+
+ /* Eat the outstanding restart() from the signaller */
+ suspend (self);
+ }
+ }
+
+ __pthread_set_own_extricate_if (self, 0);
+
+ ++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;
+}
+strong_alias (__pthread_rwlock_timedrdlock, pthread_rwlock_timedrdlock)
+
+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;
+}
+strong_alias (__pthread_rwlock_tryrdlock, pthread_rwlock_tryrdlock)
+
+
+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 */
+ }
+}
+strong_alias (__pthread_rwlock_wrlock, pthread_rwlock_wrlock)
+
+
+int
+__pthread_rwlock_timedwrlock (pthread_rwlock_t *rwlock,
+ const struct timespec *abstime)
+{
+ pthread_descr self;
+ pthread_extricate_if extr;
+
+ if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
+ return EINVAL;
+
+ self = thread_self ();
+
+ /* Set up extrication interface */
+ extr.pu_object = rwlock;
+ extr.pu_extricate_func = rwlock_wr_extricate_func;
+
+ /* Register extrication interface */
+ __pthread_set_own_extricate_if (self, &extr);
+
+ while(1)
+ {
+ __pthread_lock (&rwlock->__rw_lock, self);
+
+ if (rwlock->__rw_readers == 0 && rwlock->__rw_writer == NULL)
+ {
+ rwlock->__rw_writer = self;
+ __pthread_set_own_extricate_if (self, 0);
+ __pthread_unlock (&rwlock->__rw_lock);
+ return 0;
+ }
+
+ /* Suspend ourselves, then try again */
+ enqueue (&rwlock->__rw_write_waiting, self);
+ __pthread_unlock (&rwlock->__rw_lock);
+ /* This is not a cancellation point */
+ if (timedsuspend (self, abstime) == 0)
+ {
+ int was_on_queue;
+
+ __pthread_lock (&rwlock->__rw_lock, self);
+ was_on_queue = remove_from_queue (&rwlock->__rw_write_waiting, self);
+ __pthread_unlock (&rwlock->__rw_lock);
+
+ if (was_on_queue)
+ {
+ __pthread_set_own_extricate_if (self, 0);
+ return ETIMEDOUT;
+ }
+
+ /* Eat the outstanding restart() from the signaller */
+ suspend (self);
+ }
+ }
+}
+strong_alias (__pthread_rwlock_timedwrlock, pthread_rwlock_timedwrlock)
+
+
+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;
+}
+strong_alias (__pthread_rwlock_trywrlock, pthread_rwlock_trywrlock)
+
+
+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
+ && !queue_is_empty(&rwlock->__rw_read_waiting))
+ || (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 = THREAD_GETMEM (self, p_readlock_free);
+ THREAD_SETMEM (self, p_readlock_free, victim);
+ }
+ }
+ else
+ {
+ int val = THREAD_GETMEM (self, p_untracked_readlock_count);
+ if (val > 0)
+ THREAD_SETMEM (self, p_untracked_readlock_count, val - 1);
+ }
+ }
+ }
+
+ return 0;
+}
+strong_alias (__pthread_rwlock_unlock, pthread_rwlock_unlock)
+
+
+
+int
+pthread_rwlockattr_init (pthread_rwlockattr_t *attr)
+{
+ attr->__lockkind = 0;
+ attr->__pshared = PTHREAD_PROCESS_PRIVATE;
+
+ return 0;
+}
+
+
+int
+__pthread_rwlockattr_destroy (pthread_rwlockattr_t *attr)
+{
+ return 0;
+}
+strong_alias (__pthread_rwlockattr_destroy, pthread_rwlockattr_destroy)
+
+
+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;
+
+ /* For now it is not possible to shared a conditional variable. */
+ if (pshared != PTHREAD_PROCESS_PRIVATE)
+ return ENOSYS;
+
+ 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_PREFER_WRITER_NONRECURSIVE_NP
+ && pref != PTHREAD_RWLOCK_DEFAULT_NP)
+ return EINVAL;
+
+ attr->__lockkind = pref;
+
+ return 0;
+}
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