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145 lines
4.6 KiB
145 lines
4.6 KiB
/************************************************************************ |
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* libc/misc/lib_filesem.c |
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* |
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* Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved. |
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* Author: Gregory Nutt <gnutt@nuttx.org> |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in |
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* the documentation and/or other materials provided with the |
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* distribution. |
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* 3. Neither the name NuttX nor the names of its contributors may be |
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* used to endorse or promote products derived from this software |
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* without specific prior written permission. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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* POSSIBILITY OF SUCH DAMAGE. |
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* |
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************************************************************************/ |
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/************************************************************************ |
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* Included Files |
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************************************************************************/ |
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#include <nuttx/config.h> |
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#include <sys/types.h> |
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#include <unistd.h> |
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#include <semaphore.h> |
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#include <errno.h> |
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#include <assert.h> |
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#include "lib_internal.h" |
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#if CONFIG_STDIO_BUFFER_SIZE > 0 |
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/************************************************************************ |
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* Pre-processor Definitions |
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************************************************************************/ |
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/************************************************************************ |
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* Private Data |
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************************************************************************/ |
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/************************************************************************ |
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* Global Functions |
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************************************************************************/ |
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/************************************************************************ |
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* lib_sem_initialize |
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************************************************************************/ |
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void lib_sem_initialize(FAR struct file_struct *stream) |
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{ |
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/* Initialize the LIB semaphore to one (to support one-at- |
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* a-time access to private data sets. |
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*/ |
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(void)sem_init(&stream->fs_sem, 0, 1); |
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stream->fs_holder = -1; |
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stream->fs_counts = 0; |
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} |
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/************************************************************************ |
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* lib_take_semaphore |
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************************************************************************/ |
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void lib_take_semaphore(FAR struct file_struct *stream) |
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{ |
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pid_t my_pid = getpid(); |
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/* Do I already have the semaphore? */ |
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if (stream->fs_holder == my_pid) |
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{ |
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/* Yes, just increment the number of references that I have */ |
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stream->fs_counts++; |
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} |
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else |
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{ |
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/* Take the semaphore (perhaps waiting) */ |
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while (sem_wait(&stream->fs_sem) != 0) |
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{ |
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/* The only case that an error should occr here is if |
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* the wait was awakened by a signal. |
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*/ |
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ASSERT(get_errno() == EINTR); |
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} |
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/* We have it. Claim the stak and return */ |
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stream->fs_holder = my_pid; |
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stream->fs_counts = 1; |
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} |
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} |
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/************************************************************************ |
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* lib_give_semaphore |
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************************************************************************/ |
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void lib_give_semaphore(FAR struct file_struct *stream) |
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{ |
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pid_t my_pid = getpid(); |
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/* I better be holding at least one reference to the semaphore */ |
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ASSERT(stream->fs_holder == my_pid); |
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/* Do I hold multiple references to the semphore */ |
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if (stream->fs_counts > 1) |
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{ |
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/* Yes, just release one count and return */ |
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stream->fs_counts--; |
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} |
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else |
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{ |
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/* Nope, this is the last reference I have */ |
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stream->fs_holder = -1; |
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stream->fs_counts = 0; |
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ASSERT(sem_post(&stream->fs_sem) == 0); |
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} |
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} |
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#endif /* CONFIG_STDIO_BUFFER_SIZE */
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