/**************************************************************************** * sched/pthread/pthread_mutexlock.c * * Copyright (C) 2007-2009, 2017 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include "pthread/pthread.h" /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: pthread_mutex_lock * * Description: * The mutex object referenced by mutex is locked by calling * pthread_mutex_lock(). If the mutex is already locked, the calling thread * blocks until the mutex becomes available. This operation returns with the * mutex object referenced by mutex in the locked state with the calling * thread as its owner. * * If the mutex type is PTHREAD_MUTEX_NORMAL, deadlock detection is not * provided. Attempting to relock the mutex causes deadlock. If a thread * attempts to unlock a mutex that it has not locked or a mutex which is * unlocked, undefined behavior results. * * If the mutex type is PTHREAD_MUTEX_ERRORCHECK, then error checking is * provided. If a thread attempts to relock a mutex that it has already * locked, an error will be returned. If a thread attempts to unlock a * mutex that it has not locked or a mutex which is unlocked, an error will * be returned. * * If the mutex type is PTHREAD_MUTEX_RECURSIVE, then the mutex maintains * the concept of a lock count. When a thread successfully acquires a mutex * for the first time, the lock count is set to one. Every time a thread * relocks this mutex, the lock count is incremented by one. Each time the * thread unlocks the mutex, the lock count is decremented by one. When the * lock count reaches zero, the mutex becomes available for other threads to * acquire. If a thread attempts to unlock a mutex that it has not locked or * a mutex which is unlocked, an error will be returned. * * If a signal is delivered to a thread waiting for a mutex, upon return * from the signal handler the thread resumes waiting for the mutex as if * it was not interrupted. * * Input Parameters: * mutex - A reference to the mutex to be locked. * * Returned Value: * 0 on success or an errno value on failure. Note that the errno EINTR * is never returned by pthread_mutex_lock(). * * Assumptions: * * POSIX Compatibility: * - This implementation does not return EAGAIN when the mutex could not be * acquired because the maximum number of recursive locks for mutex has * been exceeded. * ****************************************************************************/ int pthread_mutex_lock(FAR pthread_mutex_t *mutex) { int mypid = (int)getpid(); int ret = EINVAL; sinfo("mutex=0x%p\n", mutex); DEBUGASSERT(mutex != NULL); if (mutex != NULL) { /* Make sure the semaphore is stable while we make the following * checks. This all needs to be one atomic action. */ sched_lock(); #ifdef CONFIG_PTHREAD_MUTEX_TYPES /* All mutex types except for NORMAL (and DEFAULT) will return * and an error error if the caller does not hold the mutex. */ if (mutex->type != PTHREAD_MUTEX_NORMAL && mutex->pid == mypid) { /* Yes.. Is this a recursive mutex? */ if (mutex->type == PTHREAD_MUTEX_RECURSIVE) { /* Yes... just increment the number of locks held and return * success. */ if (mutex->nlocks < INT16_MAX) { mutex->nlocks++; ret = OK; } else { ret = EOVERFLOW; } } else { /* No, then we would deadlock... return an error (default * behavior is like PTHREAD_MUTEX_ERRORCHECK) * * NOTE: This is the correct behavior for a 'robust', NORMAL * mutex. Compiant behavior for non-robust mutex should not * include these checks. In that case, it the deadlock * condition should not be detected and the thread should be * permitted to deadlock. */ serr("ERROR: Returning EDEADLK\n"); ret = EDEADLK; } } else #endif /* CONFIG_PTHREAD_MUTEX_TYPES */ #ifndef CONFIG_PTHREAD_MUTEX_UNSAFE /* The calling thread does not hold the semaphore. The correct * behavior for the 'robust' mutex is to verify that the holder of the * mutex is still valid. This is protection from the case * where the holder of the mutex has exitted without unlocking it. */ #ifdef CONFIG_PTHREAD_MUTEX_BOTH #ifdef CONFIG_PTHREAD_MUTEX_TYPES /* Include check if this is a NORMAL mutex and that it is robust */ if (mutex->pid > 0 && ((mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0 || mutex->type != PTHREAD_MUTEX_NORMAL) && sched_gettcb(mutex->pid) == NULL) #else /* CONFIG_PTHREAD_MUTEX_TYPES */ /* This can only be a NORMAL mutex. Include check if it is robust */ if (mutex->pid > 0 && (mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0 && sched_gettcb(mutex->pid) == NULL) #endif /* CONFIG_PTHREAD_MUTEX_TYPES */ #else /* CONFIG_PTHREAD_MUTEX_ROBUST */ /* This mutex is always robust, whatever type it is. */ if (mutex->pid > 0 && sched_gettcb(mutex->pid) == NULL) #endif { DEBUGASSERT(mutex->pid != 0); /* < 0: available, >0 owned, ==0 error */ DEBUGASSERT((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0); /* A thread holds the mutex, but there is no such thread. POSIX * requires that the 'robust' mutex return EOWNERDEAD in this case. * It is then the caller's responsibility to call pthread_mutx_consistent() * fo fix the mutex. */ mutex->flags |= _PTHREAD_MFLAGS_INCONSISTENT; ret = EOWNERDEAD; } else #endif /* !CONFIG_PTHREAD_MUTEX_UNSAFE */ { /* Take the underlying semaphore, waiting if necessary. NOTE that * is required to deadlock for the case of the non-robust NORMAL or * default mutex. */ ret = pthread_mutex_take(mutex, true); /* If we successfully obtained the semaphore, then indicate * that we own it. */ if (ret == OK) { mutex->pid = mypid; #ifdef CONFIG_PTHREAD_MUTEX_TYPES mutex->nlocks = 1; #endif } } sched_unlock(); } sinfo("Returning %d\n", ret); return ret; }