ipcrm behavior
Fernando Nunes asked whether ipcrm fails to remove a shared memory segment that still has attached processes. Paul Watson recalled root always removing it, though on Linux he had seen only the address zeroed with the shmid remaining. Art Kagel said the segment is killed, attached processes touching it get SIGSEGV, and it stays visible in ipcs until the last process detaches.
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Hi all, I'm looking for some feedback regarding the ipcrm behavior. I haven't used it much since we now include onclean, but I had the feeling that a long long time ago, in a galaxy such as this if we tried to remove a shared memory segment with attached processes it would fail... Man pages from ancient systems seem to contradict me... Am I just suffering from bad memory, or does anybody confirm this idea? Many thanks in advance, Regards -- Fernando Nunes Portugal http://informix-technology.blogspot.com My email works... but I don't check it frequently... --001a113ed8288dd8e205079d0aa2
Afair, when run as root, it would always take out the memory. However, recently I have seen under Linux just the address being set to zero and the shmid remaining - it might have always done that but ..... Cheers Paul Paul Watson Oninit www.oninit.com +1 913 387 7529 > On Nov 11, 2014, at 16:45, "Fernando Nunes" <domusonline@gmail.com> wrote: > > Hi all, > > I'm looking for some feedback regarding the ipcrm behavior. I haven't used > it much since we now include onclean, but I had the feeling that a long > long time ago, in a galaxy such as this if we tried to remove a shared > memory segment with attached processes it would fail... > > Man pages from ancient systems seem to contradict me... Am I just suffering > from bad memory, or does anybody confirm this idea? > > Many thanks in advance, > Regards > > -- > Fernando Nunes > Portugal > > http://informix-technology.blogspot.com > My email works... but I don't check it frequently... > > --001a113ed8288dd8e205079d0aa2 > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum.
No, if you remove a shared memory segment with ipcrm it gets killed. Processes that try to actually access it after that will get a SIGSEGV IB and crash. Processes that don't try to look at the dead memory might continue to run fine. Art Art S. Kagel, President and Principal Consultant ASK Database Management www.askdbmgt.com Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Tue, Nov 11, 2014 at 5:45 PM, Fernando Nunes <domusonline@gmail.com> wrote: > Hi all, > > I'm looking for some feedback regarding the ipcrm behavior. I haven't used > it much since we now include onclean, but I had the feeling that a long > long time ago, in a galaxy such as this if we tried to remove a shared > memory segment with attached processes it would fail... > > Man pages from ancient systems seem to contradict me... Am I just suffering > from bad memory, or does anybody confirm this idea? > > Many thanks in advance, > Regards > > -- > Fernando Nunes > Portugal > > http://informix-technology.blogspot.com > My email works... but I don't check it frequently... > > --001a113ed8288dd8e205079d0aa2 > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --047d7b34318a0ebb7d05079d98ce
You will still see the segment in ipcs until the last process detaches, but it's dead. Art Art S. Kagel, President and Principal Consultant ASK Database Management www.askdbmgt.com Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Tue, Nov 11, 2014 at 5:54 PM, Paul Watson <paul@oninit.com> wrote: > Afair, when run as root, it would always take out the memory. > > However, recently I have seen under Linux just the address being set to > zero > and the shmid remaining - it might have always done that but ..... > > Cheers > Paul > > Paul Watson > Oninit www.oninit.com > +1 913 387 7529 > > > On Nov 11, 2014, at 16:45, "Fernando Nunes" <domusonline@gmail.com> > wrote: > > > > Hi all, > > > > I'm looking for some feedback regarding the ipcrm behavior. I haven't > used > > it much since we now include onclean, but I had the feeling that a long > > long time ago, in a galaxy such as this if we tried to remove a shared > > memory segment with attached processes it would fail... > > > > Man pages from ancient systems seem to contradict me... Am I just > suffering > > from bad memory, or does anybody confirm this idea? > > > > Many thanks in advance, > > Regards > > > > -- > > Fernando Nunes > > Portugal > > > > http://informix-technology.blogspot.com > > My email works... but I don't check it frequently... > > > > --001a113ed8288dd8e205079d0aa2 > > > > > > > > ******************************************************************************* > > Forum Note: Use "Reply" to post a response in the discussion forum. > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a1134562c8e82ba05079d9af9