9b0f1823b5
now type sema_t is a structure which can be put in a shared memory area, and multiple processes can operate it concurrently. User can either use mmap(MAP_SHARED) + sem_init(pshared=1) or use sem_open() to initialize a shared semaphore. Named semaphore uses file system and is located in /tmp directory, and its file name is prefixed with 'SEMD', so now it is chroot or jail friendly. In simplist cases, both for named and un-named semaphore, userland code does not have to enter kernel to reduce/increase semaphore's count. The semaphore is designed to be crash-safe, it means even if an application is crashed in the middle of operating semaphore, the semaphore state is still safely recovered by later use, there is no waiter counter maintained by userland code. The main semaphore code is in libc and libthr only has some necessary stubs, this makes it possible that a non-threaded application can use semaphore without linking to thread library. Old semaphore implementation is kept libc to maintain binary compatibility. The kernel ksem API is no longer used in the new implemenation. Discussed on: threads@
116 lines
3.6 KiB
C
116 lines
3.6 KiB
C
/*
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* Copyright (C) 2005 David Xu <davidxu@freebsd.org>.
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* Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
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* All rights reserved.
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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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* 1. Redistributions of source code must retain the above copyright
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* notice(s), this list of conditions and the following disclaimer as
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* the first lines of this file unmodified other than the possible
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* addition of one or more copyright notices.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice(s), 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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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include "namespace.h"
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#include <sys/types.h>
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#include <sys/queue.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <pthread.h>
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#include <stdlib.h>
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#include <time.h>
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#include <_semaphore.h>
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#include "un-namespace.h"
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#include "thr_private.h"
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FB10_COMPAT(_sem_init_compat, sem_init);
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FB10_COMPAT(_sem_destroy_compat, sem_destroy);
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FB10_COMPAT(_sem_getvalue_compat, sem_getvalue);
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FB10_COMPAT(_sem_trywait_compat, sem_trywait);
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FB10_COMPAT(_sem_wait_compat, sem_wait);
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FB10_COMPAT(_sem_timedwait_compat, sem_timedwait);
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FB10_COMPAT(_sem_post_compat, sem_post);
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typedef struct sem *sem_t;
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extern int _libc_sem_init_compat(sem_t *sem, int pshared, unsigned int value);
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extern int _libc_sem_destroy_compat(sem_t *sem);
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extern int _libc_sem_getvalue_compat(sem_t * __restrict sem, int * __restrict sval);
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extern int _libc_sem_trywait_compat(sem_t *sem);
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extern int _libc_sem_wait_compat(sem_t *sem);
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extern int _libc_sem_timedwait_compat(sem_t * __restrict sem,
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const struct timespec * __restrict abstime);
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extern int _libc_sem_post_compat(sem_t *sem);
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int _sem_init_compat(sem_t *sem, int pshared, unsigned int value);
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int _sem_destroy_compat(sem_t *sem);
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int _sem_getvalue_compat(sem_t * __restrict sem, int * __restrict sval);
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int _sem_trywait_compat(sem_t *sem);
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int _sem_wait_compat(sem_t *sem);
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int _sem_timedwait_compat(sem_t * __restrict sem,
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const struct timespec * __restrict abstime);
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int _sem_post_compat(sem_t *sem);
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int
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_sem_init_compat(sem_t *sem, int pshared, unsigned int value)
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{
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return _libc_sem_init_compat(sem, pshared, value);
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}
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int
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_sem_destroy_compat(sem_t *sem)
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{
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return _libc_sem_destroy_compat(sem);
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}
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int
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_sem_getvalue_compat(sem_t * __restrict sem, int * __restrict sval)
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{
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return _libc_sem_getvalue_compat(sem, sval);
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}
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int
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_sem_trywait_compat(sem_t *sem)
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{
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return _libc_sem_trywait_compat(sem);
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}
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int
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_sem_wait_compat(sem_t *sem)
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{
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return _libc_sem_wait_compat(sem);
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}
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int
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_sem_timedwait_compat(sem_t * __restrict sem,
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const struct timespec * __restrict abstime)
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{
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return _libc_sem_timedwait_compat(sem, abstime);
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}
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int
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_sem_post_compat(sem_t *sem)
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{
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return _libc_sem_post_compat(sem);
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}
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