Very Computer

Hi,

I got a problem trying to organize simple mutual exclusion for an arbitrary
number of processes using a semaphore, on HPUX and SunOS/Solaris it works fine.

The first process opens a file gets a semaphore using semget, initializes it
semctl operation SETVAL to 1, and forks 10 children (as a test), which write
into that file.

Before writing, the children perform operation -1 on the semaphore without
UNDO or NOWAIT. After writing, they perform op 1 (without UNDO again) and
exit.

To my knowledge, this should ensure that only one process at a time writes to
that file.

Under Linux, I get the contents of the test file (fopened with mode a+) messed
up. Any idea why it works under HPUX, SunOS, Solaris and not under Linux, too?

Thanks a lot in advance,
                          Lutz.
--
-------------------------------------------

(BTW, why not just use normal file locking?)

--
James Youngman       VG Gas Analysis Systems |The trouble with the rat-race
 Before sending advertising material, read   |is, even if you win, you're
http://www.law.cornell.edu/uscode/47/227.html|still a rat.

Quote:>>I got a problem trying to organize simple mutual exclusion for an arbitrary
>>number of processes using a semaphore, on HPUX and SunOS/Solaris it works
>fine.
>>To my knowledge, this should ensure that only one process at a time writes to
>>that file.
>Are you flushing the file's stdio buffer before you release the semaphore?
>That was it, the other System don't buffer, it seems.

Quote:

>(BTW, why not just use normal file locking?)