SEM_POST(3) Linux Programmer's Manual SEM_POST(3)
NAME
sem_post - unlock a semaphore
//解锁一个信号量
SYNOPSIS
#include
int sem_post(sem_t *sem);
Link with -lrt or -pthread.
DESCRIPTION
sem_post() increments (unlocks) the semaphore pointed to by sem. If the semaphore's value consequently becomes greater than zero, then another process or thread blocked in a sem_wait(3) call will be woken up and proceed to lock the semaphore.
//sem_post() 增加(解锁)由sem指向的信号量的值.如果信号量的值因此比0大,那么另一个阻塞在sem_wait(3)上的进程或线程的调用就会被唤醒,之后锁定这个信号量.
//(译者注:因为sem_wait会使得信号量减一,开始阻塞在sem_wait()的线程当信号量sem_post()之后(信号量加一)就会被唤醒,执行之后又会被阻塞(因为信号量此时为0)).
RETURN VALUE
sem_post() returns 0 on success; on error, the value of the semaphore is left unchanged, -1 is returned, and errno is set to indicate the error.
//成功返回0,失败信号量的值不会改变,返回-1,并自动设置errno.
ERRORS
EINVAL sem is not a valid semaphore.//sem不是有效的信号量 EOVERFLOW The maximum allowable value for a semaphore would be exceeded.
//信号量允许的最大值已经超过了.
CONFORMING TO
POSIX.1-2001.
NOTES
sem_post() is async-signal-safe: it may be safely called within a signal handler.
//sem_post()是异步信号安全的:在信号处理程序内调用它是安全的.
EXAMPLE
See sem_wait(3).
SEE ALSO
sem_getvalue(3), sem_wait(3), sem_overview(7)
COLOPHON
This page is part of release 3.31 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.Linux 2009-03-30 SEM_POST(3)
