Trouble using semctl

[Neil Dunstan]

semctl( semarray_id, 0, GETNCNT, 0 ) sometimes returns 0 unexpectedly.

I'm using it in a loop to test when a process has been released from a semaphore
queue. i.e.

oldcount = semctl( semarray_id, 0, GETNCNT, 0 )
while( (newcount = semctl( semarray_id, 0, GETCNT, 0 )) != oldcount-1 )
	semop( ... /* increase semaphore value by one */

Does anyone know why this shouldn't work?

Thanks.
Newsgroups: comp.unix.internals
Subject: Problem with semctl
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semctl( semarray_id, 0, GETNCNT, 0 ) sometimes returns 0 unexpectedly.

I'm using it in a loop to test when a process has been released from a semaphore
queue. i.e.

oldcount = semctl( semarray_id, 0, GETNCNT, 0 )
while( (newcount = semctl( semarray_id, 0, GETCNT, 0 )) != oldcount-1 )
	semop( ... /* increase semaphore value by one */

Does anyone know why this shouldn't work?

Thanks.