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    SubjectRe: [RFC][PATCH 8/8] check files for checkpointability
    On Mon, 2 Mar 2009 07:37:54 -0600
    "Serge E. Hallyn" <serue@us.ibm.com> wrote:

    > Quoting Dave Hansen (dave@linux.vnet.ibm.com):
    > >
    > > 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.
    > >
    > > We also check each 'struct file' when it is installed in a fd
    > > slot. This way, if anyone open()s or managed to dup() an
    > > unsuppored file, we can catch it.
    > >
    > > Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
    >
    > So on a practical note, Ingo's scheme appears to be paying off. In
    > order for any program's files_struct to be checkpointable right now,
    > it must be statically compiled, else ld.so (I assume) looks up
    > /proc/$$/status. So since proc is not checkpointable, the result
    > is irreversibly non-checkpointable.
    >
    > So... does it make sense to mark proc as checkpointable? Do we
    > reasonably assume that the same procfile will be available at
    > restart?

    With respect to /proc/$x/* where $x is the pid the restarted task wants,
    is that not a chicken-and-egg problem?

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