diff options
Diffstat (limited to 'libc/bionic/semaphore.c')
| -rw-r--r-- | libc/bionic/semaphore.c | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/libc/bionic/semaphore.c b/libc/bionic/semaphore.c new file mode 100644 index 0000000..0c94600 --- /dev/null +++ b/libc/bionic/semaphore.c @@ -0,0 +1,212 @@ +/* + * Copyright (C) 2008 The Android Open Source Project + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * * 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. + * + * 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. + */ +#include <semaphore.h> +#include <errno.h> +#include <sys/time.h> +#include <sys/atomics.h> +#include <time.h> + +int sem_init(sem_t *sem, int pshared, unsigned int value) +{ + if (sem == NULL) { + errno = EINVAL; + return -1; + } + + if (pshared != 0) { + errno = ENOSYS; + return -1; + } + + sem->count = value; + return 0; +} + + +int sem_destroy(sem_t *sem) +{ + if (sem == NULL) { + errno = EINVAL; + return -1; + } + if (sem->count == 0) { + errno = EBUSY; + return -1; + } + return 0; +} + + +sem_t *sem_open(const char *name, int oflag, ...) +{ + name=name; + oflag=oflag; + + errno = ENOSYS; + return SEM_FAILED; +} + + +int sem_close(sem_t *sem) +{ + if (sem == NULL) { + errno = EINVAL; + return -1; + } + errno = ENOSYS; + return -1; +} + + +int sem_unlink(const char * name) +{ + errno = ENOSYS; + return -1; +} + + +static int +__atomic_dec_if_positive( volatile unsigned int* pvalue ) +{ + unsigned int old; + + do { + old = *pvalue; + } + while ( old != 0 && __atomic_cmpxchg( (int)old, (int)old-1, (volatile int*)pvalue ) != 0 ); + + return old; +} + +int sem_wait(sem_t *sem) +{ + if (sem == NULL) { + errno = EINVAL; + return -1; + } + + for (;;) { + if (__atomic_dec_if_positive(&sem->count)) + break; + + __futex_wait(&sem->count, 0, 0); + } + return 0; +} + +int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout) +{ + int ret; + + if (sem == NULL) { + errno = EINVAL; + return -1; + } + + /* POSIX says we need to try to decrement the semaphore + * before checking the timeout value */ + if (__atomic_dec_if_positive(&sem->count)) + return 0; + + /* check it as per Posix */ + if (abs_timeout == NULL || + abs_timeout->tv_sec < 0 || + abs_timeout->tv_nsec < 0 || + abs_timeout->tv_nsec >= 1000000000) + { + errno = EINVAL; + return -1; + } + + for (;;) { + struct timespec ts; + int ret; + + /* Posix mandates CLOCK_REALTIME here */ + clock_gettime( CLOCK_REALTIME, &ts ); + ts.tv_sec = abs_timeout->tv_sec - ts.tv_sec; + ts.tv_nsec = abs_timeout->tv_nsec - ts.tv_nsec; + if (ts.tv_nsec < 0) { + ts.tv_nsec += 1000000000; + ts.tv_sec -= 1; + } + + if (ts.tv_sec < 0 || ts.tv_nsec < 0) { + errno = ETIMEDOUT; + return -1; + } + + ret = __futex_wait(&sem->count, 0, &ts); + + /* return in case of timeout or interrupt */ + if (ret == -ETIMEDOUT || ret == -EINTR) { + errno = -ret; + return -1; + } + + if (__atomic_dec_if_positive(&sem->count)) + break; + } + return 0; +} + +int sem_post(sem_t *sem) +{ + if (sem == NULL) + return EINVAL; + + if (__atomic_inc((volatile int*)&sem->count) == 0) + __futex_wake(&sem->count, 1); + + return 0; +} + +int sem_trywait(sem_t *sem) +{ + if (sem == NULL) { + errno = EINVAL; + return -1; + } + + if (__atomic_dec_if_positive(&sem->count) > 0) { + return 0; + } else { + return EAGAIN; + } +} + +int sem_getvalue(sem_t *sem, int *sval) +{ + if (sem == NULL || sval == NULL) { + errno = EINVAL; + return -1; + } + + *sval = sem->count; + return 0; +} |