/**************************************************************************** * libs/libc/misc/lib_filesem.c * * Copyright (C) 2007, 2009, 2011, 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 "libc.h" #ifndef CONFIG_STDIO_DISABLE_BUFFERING /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * lib_sem_initialize ****************************************************************************/ void lib_sem_initialize(FAR struct file_struct *stream) { /* Initialize the LIB semaphore to one (to support one-at-a-time access * to private data sets. */ _SEM_INIT(&stream->fs_sem, 0, 1); stream->fs_holder = -1; stream->fs_counts = 0; } /**************************************************************************** * lib_take_semaphore ****************************************************************************/ void lib_take_semaphore(FAR struct file_struct *stream) { pid_t my_pid = getpid(); int ret; /* Do I already have the semaphore? */ if (stream->fs_holder == my_pid) { /* Yes, just increment the number of references that I have */ stream->fs_counts++; } else { /* Take the semaphore (perhaps waiting) */ while ((ret = _SEM_WAIT(&stream->fs_sem)) < 0) { /* The only case that an error should occr here is if the wait * was awakened by a signal. */ DEBUGASSERT(_SEM_ERRNO(ret) == EINTR || _SEM_ERRNO(ret) == ECANCELED); UNUSED(ret); } /* We have it. Claim the stak and return */ stream->fs_holder = my_pid; stream->fs_counts = 1; } } /**************************************************************************** * lib_give_semaphore ****************************************************************************/ void lib_give_semaphore(FAR struct file_struct *stream) { /* I better be holding at least one reference to the semaphore */ DEBUGASSERT(stream->fs_holder == getpid()); /* Do I hold multiple references to the semphore */ if (stream->fs_counts > 1) { /* Yes, just release one count and return */ stream->fs_counts--; } else { /* Nope, this is the last reference I have */ stream->fs_holder = -1; stream->fs_counts = 0; DEBUGVERIFY(_SEM_POST(&stream->fs_sem)); } } #endif /* CONFIG_STDIO_DISABLE_BUFFERING */