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lock.c
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/* Locking in multithreaded situations. Copyright (C) 2005-2008, 2015-2016 Free Software Foundation, Inc. This program 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. This program 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 this program. If not, see <http://www.gnu.org/licenses/>. */ /* Written by Bruno Haible <bruno@clisp.org>, 2005. Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h, gthr-win32.h. */ #include <config.h> #include "lock.h" /* ========================================================================= */ #if USE_POSIX_THREADS /* -------------------------- gl_lock_t datatype -------------------------- */ /* ------------------------- gl_rwlock_t datatype ------------------------- */ # if HAVE_PTHREAD_RWLOCK # if !defined PTHREAD_RWLOCK_INITIALIZER int glthread_rwlock_init_multithreaded (gl_rwlock_t *lock) { int err; err = pthread_rwlock_init (&lock->rwlock, NULL); if (err != 0) return err; lock->initialized = 1; return 0; } int glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock) { if (!lock->initialized) { int err; err = pthread_mutex_lock (&lock->guard); if (err != 0) return err; if (!lock->initialized) { err = glthread_rwlock_init_multithreaded (lock); if (err != 0) { pthread_mutex_unlock (&lock->guard); return err; } } err = pthread_mutex_unlock (&lock->guard); if (err != 0) return err; } return pthread_rwlock_rdlock (&lock->rwlock); } int glthread_rwlock_wrlock_multithreaded (gl_rwlock_t *lock) { if (!lock->initialized) { int err; err = pthread_mutex_lock (&lock->guard); if (err != 0) return err; if (!lock->initialized) { err = glthread_rwlock_init_multithreaded (lock); if (err != 0) { pthread_mutex_unlock (&lock->guard); return err; } } err = pthread_mutex_unlock (&lock->guard); if (err != 0) return err; } return pthread_rwlock_wrlock (&lock->rwlock); } int glthread_rwlock_unlock_multithreaded (gl_rwlock_t *lock) { if (!lock->initialized) return EINVAL; return pthread_rwlock_unlock (&lock->rwlock); } int glthread_rwlock_destroy_multithreaded (gl_rwlock_t *lock) { int err; if (!lock->initialized) return EINVAL; err = pthread_rwlock_destroy (&lock->rwlock); if (err != 0) return err; lock->initialized = 0; return 0; } # endif # else int glthread_rwlock_init_multithreaded (gl_rwlock_t *lock) { int err; err = pthread_mutex_init (&lock->lock, NULL); if (err != 0) return err; err = pthread_cond_init (&lock->waiting_readers, NULL); if (err != 0) return err; err = pthread_cond_init (&lock->waiting_writers, NULL); if (err != 0) return err; lock->waiting_writers_count = 0; lock->runcount = 0; return 0; } int glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock) { int err; err = pthread_mutex_lock (&lock->lock); if (err != 0) return err; /* Test whether only readers are currently running, and whether the runcount field will not overflow. */ /* POSIX says: "It is implementation-defined whether the calling thread acquires the lock when a writer does not hold the lock and there are writers blocked on the lock." Let's say, no: give the writers a higher priority. */ while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0)) { /* This thread has to wait for a while. Enqueue it among the waiting_readers. */ err = pthread_cond_wait (&lock->waiting_readers, &lock->lock); if (err != 0) { pthread_mutex_unlock (&lock->lock); return err; } } lock->runcount++; return pthread_mutex_unlock (&lock->lock); } int glthread_rwlock_wrlock_multithreaded (gl_rwlock_t *lock) { int err; err = pthread_mutex_lock (&lock->lock); if (err != 0) return err; /* 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++; err = pthread_cond_wait (&lock->waiting_writers, &lock->lock); if (err != 0) { lock->waiting_writers_count--; pthread_mutex_unlock (&lock->lock); return err; } lock->waiting_writers_count--; } lock->runcount--; /* runcount becomes -1 */ return pthread_mutex_unlock (&lock->lock); } int glthread_rwlock_unlock_multithreaded (gl_rwlock_t *lock) { int err; err = pthread_mutex_lock (&lock->lock); if (err != 0) return err; if (lock->runcount < 0) { /* Drop a writer lock. */ if (!(lock->runcount == -1)) { pthread_mutex_unlock (&lock->lock); return EINVAL; } lock->runcount = 0; } else { /* Drop a reader lock. */ if (!(lock->runcount > 0)) { pthread_mutex_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. */ err = pthread_cond_signal (&lock->waiting_writers); if (err != 0) { pthread_mutex_unlock (&lock->lock); return err; } } else { /* Wake up all waiting readers. */ err = pthread_cond_broadcast (&lock->waiting_readers); if (err != 0) { pthread_mutex_unlock (&lock->lock); return err; } } } return pthread_mutex_unlock (&lock->lock); } int glthread_rwlock_destroy_multithreaded (gl_rwlock_t *lock) { int err; err = pthread_mutex_destroy (&lock->lock); if (err != 0) return err; err = pthread_cond_destroy (&lock->waiting_readers); if (err != 0) return err; err = pthread_cond_destroy (&lock->waiting_writers); if (err != 0) return err; return 0; } # endif /* --------------------- gl_recursive_lock_t datatype --------------------- */ # if HAVE_PTHREAD_MUTEX_RECURSIVE # if defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER || defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP int glthread_recursive_lock_init_multithreaded (gl_recursive_lock_t *lock) { pthread_mutexattr_t attributes; int err; err = pthread_mutexattr_init (&attributes); if (err != 0) return err; err = pthread_mutexattr_settype (&attributes, PTHREAD_MUTEX_RECURSIVE); if (err != 0) { pthread_mutexattr_destroy (&attributes); return err; } err = pthread_mutex_init (lock, &attributes); if (err != 0) { pthread_mutexattr_destroy (&attributes); return err; } err = pthread_mutexattr_destroy (&attributes); if (err != 0) return err; return 0; } # else int glthread_recursive_lock_init_multithreaded (gl_recursive_lock_t *lock) { pthread_mutexattr_t attributes; int err; err = pthread_mutexattr_init (&attributes); if (err != 0) return err; err = pthread_mutexattr_settype (&attributes, PTHREAD_MUTEX_RECURSIVE); if (err != 0) { pthread_mutexattr_destroy (&attributes); return err; } err = pthread_mutex_init (&lock->recmutex, &attributes); if (err != 0) { pthread_mutexattr_destroy (&attributes); return err; } err = pthread_mutexattr_destroy (&attributes); if (err != 0) return err; lock->initialized = 1; return 0; } int glthread_recursive_lock_lock_multithreaded (gl_recursive_lock_t *lock) { if (!lock->initialized) { int err; err = pthread_mutex_lock (&lock->guard); if (err != 0) return err; if (!lock->initialized) { err = glthread_recursive_lock_init_multithreaded (lock); if (err != 0) { pthread_mutex_unlock (&lock->guard); return err; } } err = pthread_mutex_unlock (&lock->guard); if (err != 0) return err; } return pthread_mutex_lock (&lock->recmutex); } int glthread_recursive_lock_unlock_multithreaded (gl_recursive_lock_t *lock) { if (!lock->initialized) return EINVAL; return pthread_mutex_unlock (&lock->recmutex); } int glthread_recursive_lock_destroy_multithreaded (gl_recursive_lock_t *lock) { int err; if (!lock->initialized) return EINVAL; err = pthread_mutex_destroy (&lock->recmutex); if (err != 0) return err; lock->initialized = 0; return 0; } # endif # else int glthread_recursive_lock_init_multithreaded (gl_recursive_lock_t *lock) { int err; err = pthread_mutex_init (&lock->mutex, NULL); if (err != 0) return err; lock->owner = (pthread_t) 0; lock->depth = 0; return 0; } int glthread_recursive_lock_lock_multithreaded (gl_recursive_lock_t *lock) { pthread_t self = pthread_self (); if (lock->owner != self) { int err; err = pthread_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 != pthread_self ()) return EPERM; if (lock->depth == 0) return EINVAL; if (--(lock->depth) == 0) { lock->owner = (pthread_t) 0; return pthread_mutex_unlock (&lock->mutex); } else return 0; } int glthread_recursive_lock_destroy_multithreaded (gl_recursive_lock_t *lock) { if (lock->owner != (pthread_t) 0) return EBUSY; return pthread_mutex_destroy (&lock->mutex); } # endif /* -------------------------- gl_once_t datatype -------------------------- */ static const pthread_once_t fresh_once = PTHREAD_ONCE_INIT; int glthread_once_singlethreaded (pthread_once_t *once_control) { /* We don't know whether pthread_once_t is an integer type, a floating-point type, a pointer type, or a structure type. */ char *firstbyte = (char *)once_control; if (*firstbyte == *(const char *)&fresh_once) { /* First time use of once_control. Invert the first byte. */ *firstbyte = ~ *(const char *)&fresh_once; return 1; } else return 0; } #endif /* ========================================================================= */ #if USE_PTH_THREADS /* Use the GNU Pth threads library. */ /* -------------------------- gl_lock_t datatype -------------------------- */ /* ------------------------- gl_rwlock_t datatype ------------------------- */ /* --------------------- 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 /* ========================================================================= */ #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. */ if (!(lock->runcount + 1 > 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 /* ========================================================================= */