Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Delivered-To: mailing list cygwin@cygwin.com Message-ID: <3C4BD7EC.34D68A52@salomon.at> Date: Mon, 21 Jan 2002 09:57:16 +0100 From: Michael Haubenwallner X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.2.19 i686) X-Accept-Language: de-AT, en MIME-Version: 1.0 To: Robert Collins CC: Charles Wilson , cygwin@cygwin.com Subject: Re: cygipc-1.11 SHM-patch: fork, handling in ipc-daemon References: <3C482133.E3C673D2@salomon.at> <0a9801c1a079$4dd50e60$0200a8c0@lifelesswks> Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit X-Virus-Scanned: by AMaViS perl-11 Robert Collins wrote: > > === > ----- Original Message ----- > From: "Michael Haubenwallner" > > - It is not clear what happens in following circumstance: > > 1) the first process creates a shm > > 2) a second one attaches to it > > 3) now the second process dies without detaching > > 4) the first process removes the shm with shmctl(IPC_RMID), > > but the ipc-daemon was sleeping and did not remove the > > second attachment-entry early enough to have shm_nattch==0, > > which must be the case in shmctl() to really remove the shm > > by the caller of shmctl(IPC_RMID). > > > > What IMHO surely not should happen is that a shmid with > > shm_nattch==0 remains with having the destroy-flag set. > > So the ipc-daemon must remove a shm in this state, > > including the tmp-file. > > In this case, the daemon should wait on all the processes that are > attached, so it gets woken up when a process quits. Alternatively, you > could queue the removal, prevent now attachments, and when the second > process termination is 'noticed' perform the removal. > > Rob I forgot to say that the removal _is_ done with this patch by the daemon when the second process (meaning the last attached process) terminates, which is the 'alternative' way in your description. haubi -- Michael Haubenwallner SALOMON Automation GmbH Forschung & Entwicklung A-8114 Friesach bei Graz mailto:michael.haubenwallner@salomon.at http://www.salomon.at -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Bug reporting: http://cygwin.com/bugs.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/