[Beowulf] Shared memory and semaphores
bill at Princeton.EDU
Thu Jul 8 09:35:56 PDT 2004
When user programs end either due to a crash or sometimes even
naturally, both shared memory segments and semaphores are being left
behind on our dual processor Xeon nodes. Since users have no access to
the nodes, the cleanipcs script will not function for them as this needs
Shared memory segments are easy. One can run a script checking for user
segments and if the NATTCH field is zero, they can be removed. The
problem is in determining if the semaphores are no longer needed.
Since these are dual processor machines under PBS control, another job,
started by the same user, could become active before checks can be done
and removals start happening.
Is there a test for semaphores to determine if they are inactive? How
can I determine if one can safely be removed?
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