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Message-ID: | <3C4BD7EC.34D68A52@salomon.at> |
Date: | Mon, 21 Jan 2002 09:57:16 +0100 |
From: | Michael Haubenwallner <michael DOT haubenwallner AT salomon DOT at> |
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To: | Robert Collins <robert DOT collins AT itdomain DOT com DOT au> |
CC: | Charles Wilson <cwilson AT ece DOT gatech DOT edu>, cygwin AT cygwin DOT com |
Subject: | Re: cygipc-1.11 SHM-patch: fork, handling in ipc-daemon |
References: | <3C482133 DOT E3C673D2 AT salomon DOT at> <0a9801c1a079$4dd50e60$0200a8c0 AT lifelesswks> |
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Robert Collins wrote: > > === > ----- Original Message ----- > From: "Michael Haubenwallner" <michael DOT haubenwallner AT salomon DOT at> > > - 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 DOT haubenwallner AT salomon DOT 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/
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