msem_unlock.2 (2010 09)

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msem_unlock(2) msem_unlock(2)

NAME

msem_unlock - unlock a semaphore

SYNOPSIS

#include <sys/mman.h>

int msem_unlock(msemaphore *sem, int condition);

DESCRIPTION

msem_unlock()

unlocks a binary semaphore.

sem points to an

msemaphore structure that speciﬁes the semaphore to be unlocked.

If the condition argument is zero, the semaphore will be unlocked, whether or not any other processes are

currently attempting to lock it. If the condition argument is

MSEM_IF_WAITERS

, and some other pro-

cess is waiting to lock the semaphore or the implementation cannot reliably determine whether some pro-

cess is waiting to lock the semaphore, the semaphore is unlocked by the calling process. If the condition

argument is

MSEM_IF_WAITERS

, and no process is waiting to lock the semaphore, the semaphore is not

unlocked and an error is returned.

All calls to

msem_lock() and msem_unlock()

by multiple processes sharing a common msema-

phore structure behave as if the calls were serialized.

If the

msemaphore structure contains any value not resulting from a call to msem_init() followed

by a (possibly empty) sequence of calls to msem_lock() and msem_unlock()

, the results are

undeﬁned. The address of an

msemaphore uniquely identiﬁes the semaphore. If the msemaphore

structure contains any value copied from a msemaphore structure at a different address, the result is

undeﬁned.

IMPLEMENTATION NOTES

The system attempts to ignore or recover from invalid values placed in the

msemaphore structure, but

this is not guaranteed for all cases.

RETURN VALUE

Upon success,

msem_unlock() returns zero; otherwise, it returns −1 and sets

errno to indicate the

error.

ERRORS

msem_unlock() fails if any of the following conditions are encountered:

[EAGAIN] MSEM_IF_NOWAIT was speciﬁed and there were no waiters.

[EINVAL] sem points to an msemaphore structure that has been removed, or condition is

invalid.

[EFAULT] sem is an invalid pointer.

AUTHOR

msem_unlock() was developed by HP and OSF.

Summary of content (2 pages)

PAGE 1
msem_unlock(2) msem_unlock(2) NAME msem_unlock - unlock a semaphore SYNOPSIS #include int msem_unlock(msemaphore *sem, int condition); DESCRIPTION msem_unlock() unlocks a binary semaphore. sem points to an msemaphore structure that specifies the semaphore to be unlocked. If the condition argument is zero, the semaphore will be unlocked, whether or not any other processes are currently attempting to lock it.
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(Notes) A (Notes) mA 2 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010