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Full Discussion: semaphore removal
Top Forums UNIX for Dummies Questions & Answers semaphore removal Post 302471606 by jim mcnamara on Sunday 14th of November 2010 05:29:07 AM
Old 11-14-2010
What you are asking is not clear. The only time 600 helps is when the other processes are from another user in another group. And then they cannot do anything with the sempahore anyway, so it becomes pointless for most applications.

IMO, the real issue is: the only process that should ever be able to execute sem_init() or sem_destroy() must be the same one. The other processes should not have access to that code segment. i.e., after fork(), the child process code path does not have sem_destroy() in it. Any other plan means that one of the child processes could clobber the semaphore, the result being undefined.
 

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sem_close(3)						     Library Functions Manual						      sem_close(3)

NAME
sem_close - Deallocates the specified named semaphore (P1003.1b) LIBRARY
Realtime Library (librt.so, librt.a) SYNOPSIS
#include <semaphore.h> int sem_close ( sem_t *sem) ; PARAMETERS
sem References the semaphore to be closed. Use the sem argument returned by the previous call to sem_open. DESCRIPTION
The sem_close function makes a semaphore available for reuse by deallocating any system resources allocated for use by the current process for the named semaphore indicated by sem. If the semaphore has not been removed with a call to sem_unlink, sem_close does not change the current state of the semaphore. If the semaphore has been removed with a call to sem_unlink after the most recent call to sem_open with O_CREAT, the semaphore is no longer available after all processes that opened the semaphore close it. RETURN VALUES
On a successful call, a value of 0 (zero) is returned. Otherwise, a value of -1 is returned and errno is set to indicate that an error occurred. ERRORS
The sem_close function fails under the following condition: [EINVAL] The sem argument is not a valid semaphore descriptor. RELATED INFORMATION
Functions: sem_init(3), sem_open(3), sem_unlink(3) Guide to Realtime Programming delim off sem_close(3)
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