[Devel] Re: [PATCH 9/9][cr][v2]: Restore file-locks

[steve at chygwyn.com]

Hi,

On Tue, May 18, 2010 at 08:07:32PM -0700, Sukadev Bhattiprolu wrote:
> Restore POSIX file-locks of an application from its checkpoint image.
> 
> Read the saved file-locks from the checkpoint image and for each POSIX
> lock, call flock_set() to set the lock on the file.
> 
> As pointed out by Matt Helsley, no special handling is necessary for a
> process P2 in the checkpointed container that is blocked on a lock, L1
> held by another process P1.  Since processes in the restarted container
> begin execution only after all processes have restored. If the blocked
> process P2 is restored first, first, it will prepare to return an
> -ERESTARTSYS from the fcntl() system call, but wait for P1 to be
> restored. When P1 is restored, it will re-acquire the lock L1 before P1
> and P2 begin actual execution. This ensures that even if P2 is scheduled
> to run before P1, P2 will go back to waiting for the lock L1.
>
Does that imply certain conditions wrt checkpointed processes and
NFS exports? I'm not sure I exactly undertstand the use case which
this is intended to address.

I was hoping to figure out whether it would also still be safe on
a cluster filesystem as well,

Steve.
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