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Diffstat (limited to 'linuxthreads/man/sem_init.man')
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diff --git a/linuxthreads/man/sem_init.man b/linuxthreads/man/sem_init.man deleted file mode 100644 index e3a1a63e36..0000000000 --- a/linuxthreads/man/sem_init.man +++ /dev/null @@ -1,132 +0,0 @@ -.TH SEMAPHORES 3 LinuxThreads - -.XREF sem_wait -.XREF sem_trywait -.XREF sem_post -.XREF sem_getvalue -.XREF sem_destroy - -.SH NAME -sem_init, sem_wait, sem_trywait, sem_post, sem_getvalue, sem_destroy \- operations on semaphores - -.SH SYNOPSIS -#include <semaphore.h> - -int sem_init(sem_t *sem, int pshared, unsigned int value); - -int sem_wait(sem_t * sem); - -int sem_trywait(sem_t * sem); - -int sem_post(sem_t * sem); - -int sem_getvalue(sem_t * sem, int * sval); - -int sem_destroy(sem_t * sem); - -.SH DESCRIPTION -This manual page documents POSIX 1003.1b semaphores, not to be -confused with SystemV semaphores as described in !ipc!(5), !semctl!(2) -and !semop!(2). - -Semaphores are counters for resources shared between threads. The -basic operations on semaphores are: increment the counter atomically, -and wait until the counter is non-null and decrement it atomically. - -!sem_init! initializes the semaphore object pointed to by |sem|. The -count associated with the semaphore is set initially to |value|. The -|pshared| argument indicates whether the semaphore is local to the -current process (|pshared| is zero) or is to be shared between several -processes (|pshared| is not zero). LinuxThreads currently does not -support process-shared semaphores, thus !sem_init! always returns with -error !ENOSYS! if |pshared| is not zero. - -!sem_wait! suspends the calling thread until the semaphore pointed to -by |sem| has non-zero count. It then atomically decreases the -semaphore count. - -!sem_trywait! is a non-blocking variant of !sem_wait!. If the -semaphore pointed to by |sem| has non-zero count, the count is -atomically decreased and !sem_trywait! immediately returns 0. -If the semaphore count is zero, !sem_trywait! immediately returns with -error !EAGAIN!. - -!sem_post! atomically increases the count of the semaphore pointed to -by |sem|. This function never blocks and can safely be used in -asynchronous signal handlers. - -!sem_getvalue! stores in the location pointed to by |sval| the current -count of the semaphore |sem|. - -!sem_destroy! destroys a semaphore object, freeing the resources it -might hold. No threads should be waiting on the semaphore at the time -!sem_destroy! is called. In the LinuxThreads implementation, no -resources are associated with semaphore objects, thus !sem_destroy! -actually does nothing except checking that no thread is waiting on the -semaphore. - -.SH CANCELLATION - -!sem_wait! is a cancellation point. - -.SH "ASYNC-SIGNAL SAFETY" - -On processors supporting atomic compare-and-swap (Intel 486, Pentium -and later, Alpha, PowerPC, MIPS II, Motorola 68k), the !sem_post! -function is async-signal safe and can therefore be -called from signal handlers. This is the only thread synchronization -function provided by POSIX threads that is async-signal safe. - -On the Intel 386 and the Sparc, the current LinuxThreads -implementation of !sem_post! is not async-signal safe by lack of the -required atomic operations. - -.SH "RETURN VALUE" - -The !sem_wait! and !sem_getvalue! functions always return 0. -All other semaphore functions return 0 on success and -1 on error, in -addition to writing an error code in !errno!. - -.SH ERRORS - -The !sem_init! function sets !errno! to the following codes on error: -.RS -.TP -!EINVAL! -|value| exceeds the maximal counter value !SEM_VALUE_MAX! -.TP -!ENOSYS! -|pshared| is not zero -.RE - -The !sem_trywait! function sets !errno! to the following error code on error: -.RS -.TP -!EAGAIN! -the semaphore count is currently 0 -.RE - -The !sem_post! function sets !errno! to the following error code on error: -.RS -.TP -!ERANGE! -after incrementation, the semaphore value would exceed !SEM_VALUE_MAX! -(the semaphore count is left unchanged in this case) -.RE - -The !sem_destroy! function sets !errno! to the following error code on error: -.RS -.TP -!EBUSY! -some threads are currently blocked waiting on the semaphore. -.RE - -.SH AUTHOR -Xavier Leroy <Xavier.Leroy@inria.fr> - -.SH "SEE ALSO" -!pthread_mutex_init!(3), -!pthread_cond_init!(3), -!pthread_cancel!(3), -!ipc!(5). - |