Messages in this thread | | | Date | Sun, 1 Mar 2009 11:00:10 -0600 | From | "Serge E. Hallyn" <> | Subject | Re: [RFC][PATCH 8/8] check files for checkpointability |
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Quoting Sukadev Bhattiprolu (sukadev@linux.vnet.ibm.com): > Dave Hansen [dave@linux.vnet.ibm.com] wrote: > | > | Introduce a files_struct counter to indicate whether a particular > | file_struct has ever contained a file which can not be > | checkpointed. This flag is a one-way trip; once it is set, it may > | not be unset. > | > | We assume at allocation that a new files_struct is clean and may > | be checkpointed. However, as soon as it has had its files filled > | from its parent's, we check it for real in __scan_files_for_cr(). > | At that point, we mark it if it contained any uncheckpointable > | files. > > Hmm. Why not just copy ->may_checkpoint setting from parent (or old) > files_struct ? If parent is not checkpointable, then child won't be > and vice-versa - no ?
No. We don't clear the files_struct checkpointable flag when an uncheckpointable file is closed. But if the parent has closed all uncheckpointable files before forking, then the child can be started with a checkpointable files_struct.
Otherwise it wouldn't just be the task which has a one-way trip to uncheckpointability, but process trees, and - assuming init does anything uncheckpointable at all - the whole system :)
-serge
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