From be8efac78d067c138ad8dda03df4336e73f94887 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Sat, 8 Jan 2022 11:51:07 +0100 Subject: New upstream version 1.0 --- lib/glthread/lock.c | 973 +++++++++++++--------------------------------------- 1 file changed, 246 insertions(+), 727 deletions(-) (limited to 'lib/glthread/lock.c') diff --git a/lib/glthread/lock.c b/lib/glthread/lock.c index 9e148910..b650c219 100644 --- a/lib/glthread/lock.c +++ b/lib/glthread/lock.c @@ -1,31 +1,21 @@ /* Locking in multithreaded situations. - Copyright (C) 2005-2018 Free Software Foundation, Inc. + Copyright (C) 2005-2022 Free Software Foundation, Inc. - This program is free software: you can redistribute it and/or - modify it under the terms of either: + This file 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 Lesser General Public License as published by the Free - Software Foundation; either version 3 of the License, or (at your - option) any later version. - - or - - * the GNU General Public License as published by the Free - Software Foundation; either version 2 of the License, or (at your - option) any later version. - - or both in parallel, as here. - This program is distributed in the hope that it will be useful, + This file 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 General Public License for more details. + GNU Lesser General Public License for more details. - You should have received a copy of the GNU General Public License - along with this program; if not, see . */ + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see . */ /* Written by Bruno Haible , 2005. - Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h, - gthr-win32.h. */ + Based on GCC's gthr-posix.h, gthr-posix95.h. */ #include @@ -33,6 +23,229 @@ /* ========================================================================= */ +#if USE_ISOC_THREADS || USE_ISOC_AND_POSIX_THREADS + +/* -------------------------- gl_lock_t datatype -------------------------- */ + +int +glthread_lock_init (gl_lock_t *lock) +{ + if (mtx_init (&lock->mutex, mtx_plain) != thrd_success) + return ENOMEM; + lock->init_needed = 0; + return 0; +} + +int +glthread_lock_lock (gl_lock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + if (mtx_lock (&lock->mutex) != thrd_success) + return EAGAIN; + return 0; +} + +int +glthread_lock_unlock (gl_lock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + if (mtx_unlock (&lock->mutex) != thrd_success) + return EINVAL; + return 0; +} + +int +glthread_lock_destroy (gl_lock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + mtx_destroy (&lock->mutex); + return 0; +} + +/* ------------------------- gl_rwlock_t datatype ------------------------- */ + +int +glthread_rwlock_init (gl_rwlock_t *lock) +{ + if (mtx_init (&lock->lock, mtx_plain) != thrd_success + || cnd_init (&lock->waiting_readers) != thrd_success + || cnd_init (&lock->waiting_writers) != thrd_success) + return ENOMEM; + lock->waiting_writers_count = 0; + lock->runcount = 0; + lock->init_needed = 0; + return 0; +} + +int +glthread_rwlock_rdlock (gl_rwlock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + if (mtx_lock (&lock->lock) != thrd_success) + return EAGAIN; + /* Test whether only readers are currently running, and whether the runcount + field will not overflow, and whether no writer is waiting. The latter + condition is because POSIX recommends that "write locks shall take + precedence over read locks", to avoid "writer starvation". */ + while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0)) + { + /* This thread has to wait for a while. Enqueue it among the + waiting_readers. */ + if (cnd_wait (&lock->waiting_readers, &lock->lock) != thrd_success) + { + mtx_unlock (&lock->lock); + return EINVAL; + } + } + lock->runcount++; + if (mtx_unlock (&lock->lock) != thrd_success) + return EINVAL; + return 0; +} + +int +glthread_rwlock_wrlock (gl_rwlock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + if (mtx_lock (&lock->lock) != thrd_success) + return EAGAIN; + /* Test whether no readers or writers are currently running. */ + while (!(lock->runcount == 0)) + { + /* This thread has to wait for a while. Enqueue it among the + waiting_writers. */ + lock->waiting_writers_count++; + if (cnd_wait (&lock->waiting_writers, &lock->lock) != thrd_success) + { + lock->waiting_writers_count--; + mtx_unlock (&lock->lock); + return EINVAL; + } + lock->waiting_writers_count--; + } + lock->runcount--; /* runcount becomes -1 */ + if (mtx_unlock (&lock->lock) != thrd_success) + return EINVAL; + return 0; +} + +int +glthread_rwlock_unlock (gl_rwlock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + if (mtx_lock (&lock->lock) != thrd_success) + return EAGAIN; + if (lock->runcount < 0) + { + /* Drop a writer lock. */ + if (!(lock->runcount == -1)) + { + mtx_unlock (&lock->lock); + return EINVAL; + } + lock->runcount = 0; + } + else + { + /* Drop a reader lock. */ + if (!(lock->runcount > 0)) + { + mtx_unlock (&lock->lock); + return EINVAL; + } + lock->runcount--; + } + if (lock->runcount == 0) + { + /* POSIX recommends that "write locks shall take precedence over read + locks", to avoid "writer starvation". */ + if (lock->waiting_writers_count > 0) + { + /* Wake up one of the waiting writers. */ + if (cnd_signal (&lock->waiting_writers) != thrd_success) + { + mtx_unlock (&lock->lock); + return EINVAL; + } + } + else + { + /* Wake up all waiting readers. */ + if (cnd_broadcast (&lock->waiting_readers) != thrd_success) + { + mtx_unlock (&lock->lock); + return EINVAL; + } + } + } + if (mtx_unlock (&lock->lock) != thrd_success) + return EINVAL; + return 0; +} + +int +glthread_rwlock_destroy (gl_rwlock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + mtx_destroy (&lock->lock); + cnd_destroy (&lock->waiting_readers); + cnd_destroy (&lock->waiting_writers); + return 0; +} + +/* --------------------- gl_recursive_lock_t datatype --------------------- */ + +int +glthread_recursive_lock_init (gl_recursive_lock_t *lock) +{ + if (mtx_init (&lock->mutex, mtx_plain | mtx_recursive) != thrd_success) + return ENOMEM; + lock->init_needed = 0; + return 0; +} + +int +glthread_recursive_lock_lock (gl_recursive_lock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + if (mtx_lock (&lock->mutex) != thrd_success) + return EAGAIN; + return 0; +} + +int +glthread_recursive_lock_unlock (gl_recursive_lock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + if (mtx_unlock (&lock->mutex) != thrd_success) + return EINVAL; + return 0; +} + +int +glthread_recursive_lock_destroy (gl_recursive_lock_t *lock) +{ + if (lock->init_needed) + call_once (&lock->init_once, lock->init_func); + mtx_destroy (&lock->mutex); + return 0; +} + +/* -------------------------- gl_once_t datatype -------------------------- */ + +#endif + +/* ========================================================================= */ + #if USE_POSIX_THREADS /* -------------------------- gl_lock_t datatype -------------------------- */ @@ -41,7 +254,7 @@ # if HAVE_PTHREAD_RWLOCK && (HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER || (defined PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP && (__GNU_LIBRARY__ > 1))) -# ifdef PTHREAD_RWLOCK_INITIALIZER +# if defined PTHREAD_RWLOCK_INITIALIZER || defined PTHREAD_RWLOCK_INITIALIZER_NP # if !HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER /* glibc with bug https://sourceware.org/bugzilla/show_bug.cgi?id=13701 */ @@ -505,726 +718,32 @@ glthread_once_singlethreaded (pthread_once_t *once_control) return 0; } -#endif - -/* ========================================================================= */ - -#if USE_PTH_THREADS - -/* Use the GNU Pth threads library. */ - -/* -------------------------- gl_lock_t datatype -------------------------- */ - -/* ------------------------- gl_rwlock_t datatype ------------------------- */ - -# if !HAVE_PTH_RWLOCK_ACQUIRE_PREFER_WRITER - -int -glthread_rwlock_init_multithreaded (gl_rwlock_t *lock) -{ - if (!pth_mutex_init (&lock->lock)) - return errno; - if (!pth_cond_init (&lock->waiting_readers)) - return errno; - if (!pth_cond_init (&lock->waiting_writers)) - return errno; - lock->waiting_writers_count = 0; - lock->runcount = 0; - lock->initialized = 1; - return 0; -} - -int -glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock) -{ - if (!lock->initialized) - glthread_rwlock_init_multithreaded (lock); - if (!pth_mutex_acquire (&lock->lock, 0, NULL)) - return errno; - /* Test whether only readers are currently running, and whether the runcount - field will not overflow, and whether no writer is waiting. The latter - condition is because POSIX recommends that "write locks shall take - precedence over read locks", to avoid "writer starvation". */ - while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0)) - { - /* This thread has to wait for a while. Enqueue it among the - waiting_readers. */ - if (!pth_cond_await (&lock->waiting_readers, &lock->lock, NULL)) - { - int err = errno; - pth_mutex_release (&lock->lock); - return err; - } - } - lock->runcount++; - return (!pth_mutex_release (&lock->lock) ? errno : 0); -} - -int -glthread_rwlock_wrlock_multithreaded (gl_rwlock_t *lock) -{ - if (!lock->initialized) - glthread_rwlock_init_multithreaded (lock); - if (!pth_mutex_acquire (&lock->lock, 0, NULL)) - return errno; - /* Test whether no readers or writers are currently running. */ - while (!(lock->runcount == 0)) - { - /* This thread has to wait for a while. Enqueue it among the - waiting_writers. */ - lock->waiting_writers_count++; - if (!pth_cond_await (&lock->waiting_writers, &lock->lock, NULL)) - { - int err = errno; - lock->waiting_writers_count--; - pth_mutex_release (&lock->lock); - return err; - } - lock->waiting_writers_count--; - } - lock->runcount--; /* runcount becomes -1 */ - return (!pth_mutex_release (&lock->lock) ? errno : 0); -} +# if !(PTHREAD_IN_USE_DETECTION_HARD || USE_POSIX_THREADS_WEAK) int -glthread_rwlock_unlock_multithreaded (gl_rwlock_t *lock) +glthread_once_multithreaded (pthread_once_t *once_control, + void (*init_function) (void)) { - int err; - - if (!lock->initialized) - return EINVAL; - if (!pth_mutex_acquire (&lock->lock, 0, NULL)) - return errno; - if (lock->runcount < 0) - { - /* Drop a writer lock. */ - if (!(lock->runcount == -1)) - { - pth_mutex_release (&lock->lock); - return EINVAL; - } - lock->runcount = 0; - } - else - { - /* Drop a reader lock. */ - if (!(lock->runcount > 0)) - { - pth_mutex_release (&lock->lock); - return EINVAL; - } - lock->runcount--; - } - if (lock->runcount == 0) + int err = pthread_once (once_control, init_function); + if (err == ENOSYS) { - /* POSIX recommends that "write locks shall take precedence over read - locks", to avoid "writer starvation". */ - if (lock->waiting_writers_count > 0) - { - /* Wake up one of the waiting writers. */ - if (!pth_cond_notify (&lock->waiting_writers, FALSE)) - { - int err = errno; - pth_mutex_release (&lock->lock); - return err; - } - } - else - { - /* Wake up all waiting readers. */ - if (!pth_cond_notify (&lock->waiting_readers, TRUE)) - { - int err = errno; - pth_mutex_release (&lock->lock); - return err; - } - } + /* This happens on FreeBSD 11: The pthread_once function in libc returns + ENOSYS. */ + if (glthread_once_singlethreaded (once_control)) + init_function (); + return 0; } - return (!pth_mutex_release (&lock->lock) ? errno : 0); -} - -int -glthread_rwlock_destroy_multithreaded (gl_rwlock_t *lock) -{ - lock->initialized = 0; - return 0; + return err; } # endif -/* --------------------- gl_recursive_lock_t datatype --------------------- */ - -/* -------------------------- gl_once_t datatype -------------------------- */ - -static void -glthread_once_call (void *arg) -{ - void (**gl_once_temp_addr) (void) = (void (**) (void)) arg; - void (*initfunction) (void) = *gl_once_temp_addr; - initfunction (); -} - -int -glthread_once_multithreaded (pth_once_t *once_control, void (*initfunction) (void)) -{ - void (*temp) (void) = initfunction; - return (!pth_once (once_control, glthread_once_call, &temp) ? errno : 0); -} - -int -glthread_once_singlethreaded (pth_once_t *once_control) -{ - /* We know that pth_once_t is an integer type. */ - if (*once_control == PTH_ONCE_INIT) - { - /* First time use of once_control. Invert the marker. */ - *once_control = ~ PTH_ONCE_INIT; - return 1; - } - else - return 0; -} - -#endif - -/* ========================================================================= */ - -#if USE_SOLARIS_THREADS - -/* Use the old Solaris threads library. */ - -/* -------------------------- gl_lock_t datatype -------------------------- */ - -/* ------------------------- gl_rwlock_t datatype ------------------------- */ - -/* --------------------- gl_recursive_lock_t datatype --------------------- */ - -int -glthread_recursive_lock_init_multithreaded (gl_recursive_lock_t *lock) -{ - int err; - - err = mutex_init (&lock->mutex, USYNC_THREAD, NULL); - if (err != 0) - return err; - lock->owner = (thread_t) 0; - lock->depth = 0; - return 0; -} - -int -glthread_recursive_lock_lock_multithreaded (gl_recursive_lock_t *lock) -{ - thread_t self = thr_self (); - if (lock->owner != self) - { - int err; - - err = mutex_lock (&lock->mutex); - if (err != 0) - return err; - lock->owner = self; - } - if (++(lock->depth) == 0) /* wraparound? */ - { - lock->depth--; - return EAGAIN; - } - return 0; -} - -int -glthread_recursive_lock_unlock_multithreaded (gl_recursive_lock_t *lock) -{ - if (lock->owner != thr_self ()) - return EPERM; - if (lock->depth == 0) - return EINVAL; - if (--(lock->depth) == 0) - { - lock->owner = (thread_t) 0; - return mutex_unlock (&lock->mutex); - } - else - return 0; -} - -int -glthread_recursive_lock_destroy_multithreaded (gl_recursive_lock_t *lock) -{ - if (lock->owner != (thread_t) 0) - return EBUSY; - return mutex_destroy (&lock->mutex); -} - -/* -------------------------- gl_once_t datatype -------------------------- */ - -int -glthread_once_multithreaded (gl_once_t *once_control, void (*initfunction) (void)) -{ - if (!once_control->inited) - { - int err; - - /* Use the mutex to guarantee that if another thread is already calling - the initfunction, this thread waits until it's finished. */ - err = mutex_lock (&once_control->mutex); - if (err != 0) - return err; - if (!once_control->inited) - { - once_control->inited = 1; - initfunction (); - } - return mutex_unlock (&once_control->mutex); - } - else - return 0; -} - -int -glthread_once_singlethreaded (gl_once_t *once_control) -{ - /* We know that gl_once_t contains an integer type. */ - if (!once_control->inited) - { - /* First time use of once_control. Invert the marker. */ - once_control->inited = ~ 0; - return 1; - } - else - return 0; -} - -#endif +#endif /* ========================================================================= */ #if USE_WINDOWS_THREADS -/* -------------------------- gl_lock_t datatype -------------------------- */ - -void -glthread_lock_init_func (gl_lock_t *lock) -{ - InitializeCriticalSection (&lock->lock); - lock->guard.done = 1; -} - -int -glthread_lock_lock_func (gl_lock_t *lock) -{ - if (!lock->guard.done) - { - if (InterlockedIncrement (&lock->guard.started) == 0) - /* This thread is the first one to need this lock. Initialize it. */ - glthread_lock_init (lock); - else - /* Yield the CPU while waiting for another thread to finish - initializing this lock. */ - while (!lock->guard.done) - Sleep (0); - } - EnterCriticalSection (&lock->lock); - return 0; -} - -int -glthread_lock_unlock_func (gl_lock_t *lock) -{ - if (!lock->guard.done) - return EINVAL; - LeaveCriticalSection (&lock->lock); - return 0; -} - -int -glthread_lock_destroy_func (gl_lock_t *lock) -{ - if (!lock->guard.done) - return EINVAL; - DeleteCriticalSection (&lock->lock); - lock->guard.done = 0; - return 0; -} - -/* ------------------------- gl_rwlock_t datatype ------------------------- */ - -/* In this file, the waitqueues are implemented as circular arrays. */ -#define gl_waitqueue_t gl_carray_waitqueue_t - -static void -gl_waitqueue_init (gl_waitqueue_t *wq) -{ - wq->array = NULL; - wq->count = 0; - wq->alloc = 0; - wq->offset = 0; -} - -/* Enqueues the current thread, represented by an event, in a wait queue. - Returns INVALID_HANDLE_VALUE if an allocation failure occurs. */ -static HANDLE -gl_waitqueue_add (gl_waitqueue_t *wq) -{ - HANDLE event; - unsigned int index; - - if (wq->count == wq->alloc) - { - unsigned int new_alloc = 2 * wq->alloc + 1; - HANDLE *new_array = - (HANDLE *) realloc (wq->array, new_alloc * sizeof (HANDLE)); - if (new_array == NULL) - /* No more memory. */ - return INVALID_HANDLE_VALUE; - /* Now is a good opportunity to rotate the array so that its contents - starts at offset 0. */ - if (wq->offset > 0) - { - unsigned int old_count = wq->count; - unsigned int old_alloc = wq->alloc; - unsigned int old_offset = wq->offset; - unsigned int i; - if (old_offset + old_count > old_alloc) - { - unsigned int limit = old_offset + old_count - old_alloc; - for (i = 0; i < limit; i++) - new_array[old_alloc + i] = new_array[i]; - } - for (i = 0; i < old_count; i++) - new_array[i] = new_array[old_offset + i]; - wq->offset = 0; - } - wq->array = new_array; - wq->alloc = new_alloc; - } - /* Whether the created event is a manual-reset one or an auto-reset one, - does not matter, since we will wait on it only once. */ - event = CreateEvent (NULL, TRUE, FALSE, NULL); - if (event == INVALID_HANDLE_VALUE) - /* No way to allocate an event. */ - return INVALID_HANDLE_VALUE; - index = wq->offset + wq->count; - if (index >= wq->alloc) - index -= wq->alloc; - wq->array[index] = event; - wq->count++; - return event; -} - -/* Notifies the first thread from a wait queue and dequeues it. */ -static void -gl_waitqueue_notify_first (gl_waitqueue_t *wq) -{ - SetEvent (wq->array[wq->offset + 0]); - wq->offset++; - wq->count--; - if (wq->count == 0 || wq->offset == wq->alloc) - wq->offset = 0; -} - -/* Notifies all threads from a wait queue and dequeues them all. */ -static void -gl_waitqueue_notify_all (gl_waitqueue_t *wq) -{ - unsigned int i; - - for (i = 0; i < wq->count; i++) - { - unsigned int index = wq->offset + i; - if (index >= wq->alloc) - index -= wq->alloc; - SetEvent (wq->array[index]); - } - wq->count = 0; - wq->offset = 0; -} - -void -glthread_rwlock_init_func (gl_rwlock_t *lock) -{ - InitializeCriticalSection (&lock->lock); - gl_waitqueue_init (&lock->waiting_readers); - gl_waitqueue_init (&lock->waiting_writers); - lock->runcount = 0; - lock->guard.done = 1; -} - -int -glthread_rwlock_rdlock_func (gl_rwlock_t *lock) -{ - if (!lock->guard.done) - { - if (InterlockedIncrement (&lock->guard.started) == 0) - /* This thread is the first one to need this lock. Initialize it. */ - glthread_rwlock_init (lock); - else - /* Yield the CPU while waiting for another thread to finish - initializing this lock. */ - while (!lock->guard.done) - Sleep (0); - } - EnterCriticalSection (&lock->lock); - /* Test whether only readers are currently running, and whether the runcount - field will not overflow, and whether no writer is waiting. The latter - condition is because POSIX recommends that "write locks shall take - precedence over read locks", to avoid "writer starvation". */ - if (!(lock->runcount + 1 > 0 && lock->waiting_writers.count == 0)) - { - /* This thread has to wait for a while. Enqueue it among the - waiting_readers. */ - HANDLE event = gl_waitqueue_add (&lock->waiting_readers); - if (event != INVALID_HANDLE_VALUE) - { - DWORD result; - LeaveCriticalSection (&lock->lock); - /* Wait until another thread signals this event. */ - result = WaitForSingleObject (event, INFINITE); - if (result == WAIT_FAILED || result == WAIT_TIMEOUT) - abort (); - CloseHandle (event); - /* The thread which signalled the event already did the bookkeeping: - removed us from the waiting_readers, incremented lock->runcount. */ - if (!(lock->runcount > 0)) - abort (); - return 0; - } - else - { - /* Allocation failure. Weird. */ - do - { - LeaveCriticalSection (&lock->lock); - Sleep (1); - EnterCriticalSection (&lock->lock); - } - while (!(lock->runcount + 1 > 0)); - } - } - lock->runcount++; - LeaveCriticalSection (&lock->lock); - return 0; -} - -int -glthread_rwlock_wrlock_func (gl_rwlock_t *lock) -{ - if (!lock->guard.done) - { - if (InterlockedIncrement (&lock->guard.started) == 0) - /* This thread is the first one to need this lock. Initialize it. */ - glthread_rwlock_init (lock); - else - /* Yield the CPU while waiting for another thread to finish - initializing this lock. */ - while (!lock->guard.done) - Sleep (0); - } - EnterCriticalSection (&lock->lock); - /* Test whether no readers or writers are currently running. */ - if (!(lock->runcount == 0)) - { - /* This thread has to wait for a while. Enqueue it among the - waiting_writers. */ - HANDLE event = gl_waitqueue_add (&lock->waiting_writers); - if (event != INVALID_HANDLE_VALUE) - { - DWORD result; - LeaveCriticalSection (&lock->lock); - /* Wait until another thread signals this event. */ - result = WaitForSingleObject (event, INFINITE); - if (result == WAIT_FAILED || result == WAIT_TIMEOUT) - abort (); - CloseHandle (event); - /* The thread which signalled the event already did the bookkeeping: - removed us from the waiting_writers, set lock->runcount = -1. */ - if (!(lock->runcount == -1)) - abort (); - return 0; - } - else - { - /* Allocation failure. Weird. */ - do - { - LeaveCriticalSection (&lock->lock); - Sleep (1); - EnterCriticalSection (&lock->lock); - } - while (!(lock->runcount == 0)); - } - } - lock->runcount--; /* runcount becomes -1 */ - LeaveCriticalSection (&lock->lock); - return 0; -} - -int -glthread_rwlock_unlock_func (gl_rwlock_t *lock) -{ - if (!lock->guard.done) - return EINVAL; - EnterCriticalSection (&lock->lock); - if (lock->runcount < 0) - { - /* Drop a writer lock. */ - if (!(lock->runcount == -1)) - abort (); - lock->runcount = 0; - } - else - { - /* Drop a reader lock. */ - if (!(lock->runcount > 0)) - { - LeaveCriticalSection (&lock->lock); - return EPERM; - } - lock->runcount--; - } - if (lock->runcount == 0) - { - /* POSIX recommends that "write locks shall take precedence over read - locks", to avoid "writer starvation". */ - if (lock->waiting_writers.count > 0) - { - /* Wake up one of the waiting writers. */ - lock->runcount--; - gl_waitqueue_notify_first (&lock->waiting_writers); - } - else - { - /* Wake up all waiting readers. */ - lock->runcount += lock->waiting_readers.count; - gl_waitqueue_notify_all (&lock->waiting_readers); - } - } - LeaveCriticalSection (&lock->lock); - return 0; -} - -int -glthread_rwlock_destroy_func (gl_rwlock_t *lock) -{ - if (!lock->guard.done) - return EINVAL; - if (lock->runcount != 0) - return EBUSY; - DeleteCriticalSection (&lock->lock); - if (lock->waiting_readers.array != NULL) - free (lock->waiting_readers.array); - if (lock->waiting_writers.array != NULL) - free (lock->waiting_writers.array); - lock->guard.done = 0; - return 0; -} - -/* --------------------- gl_recursive_lock_t datatype --------------------- */ - -void -glthread_recursive_lock_init_func (gl_recursive_lock_t *lock) -{ - lock->owner = 0; - lock->depth = 0; - InitializeCriticalSection (&lock->lock); - lock->guard.done = 1; -} - -int -glthread_recursive_lock_lock_func (gl_recursive_lock_t *lock) -{ - if (!lock->guard.done) - { - if (InterlockedIncrement (&lock->guard.started) == 0) - /* This thread is the first one to need this lock. Initialize it. */ - glthread_recursive_lock_init (lock); - else - /* Yield the CPU while waiting for another thread to finish - initializing this lock. */ - while (!lock->guard.done) - Sleep (0); - } - { - DWORD self = GetCurrentThreadId (); - if (lock->owner != self) - { - EnterCriticalSection (&lock->lock); - lock->owner = self; - } - if (++(lock->depth) == 0) /* wraparound? */ - { - lock->depth--; - return EAGAIN; - } - } - return 0; -} - -int -glthread_recursive_lock_unlock_func (gl_recursive_lock_t *lock) -{ - if (lock->owner != GetCurrentThreadId ()) - return EPERM; - if (lock->depth == 0) - return EINVAL; - if (--(lock->depth) == 0) - { - lock->owner = 0; - LeaveCriticalSection (&lock->lock); - } - return 0; -} - -int -glthread_recursive_lock_destroy_func (gl_recursive_lock_t *lock) -{ - if (lock->owner != 0) - return EBUSY; - DeleteCriticalSection (&lock->lock); - lock->guard.done = 0; - return 0; -} - -/* -------------------------- gl_once_t datatype -------------------------- */ - -void -glthread_once_func (gl_once_t *once_control, void (*initfunction) (void)) -{ - if (once_control->inited <= 0) - { - if (InterlockedIncrement (&once_control->started) == 0) - { - /* This thread is the first one to come to this once_control. */ - InitializeCriticalSection (&once_control->lock); - EnterCriticalSection (&once_control->lock); - once_control->inited = 0; - initfunction (); - once_control->inited = 1; - LeaveCriticalSection (&once_control->lock); - } - else - { - /* Undo last operation. */ - InterlockedDecrement (&once_control->started); - /* Some other thread has already started the initialization. - Yield the CPU while waiting for the other thread to finish - initializing and taking the lock. */ - while (once_control->inited < 0) - Sleep (0); - if (once_control->inited <= 0) - { - /* Take the lock. This blocks until the other thread has - finished calling the initfunction. */ - EnterCriticalSection (&once_control->lock); - LeaveCriticalSection (&once_control->lock); - if (!(once_control->inited > 0)) - abort (); - } - } - } -} - #endif /* ========================================================================= */ -- cgit v1.2.3