Emacs20 and mail file locking.

[Rob Browning <rlb@cs.utexas.edu>]

My question is, should I modify emacs to use maillock from liblockdev,
or it the emacs mechanism OK (what about NFS)?

My reading is that emacs needs to be modified, but since liblockdev
requires you to call touchlock on a regular basis, I'm worried that
the modification might be non-trivial.

Here's the relevant bit from the Emacs config:

  /* define MAIL_USE_FLOCK if the mailer uses flock
     to interlock access to /usr/spool/mail/$USER.
     The alternative is that a lock file named
     /usr/spool/mail/$USER.lock.  */

  /* On GNU/Linux systems, both methods are used by various mail
     programs.  I assume that most people are using newer mailers that
     have heard of flock.  Change this if you need to. */

  #define MAIL_USE_FLOCK

And here's the relevant bit from debian-policy:

     All Debian MUAs and MTAs have to use the `maillock' and `mailunlock'
     functions provided by the `liblockfile' packages to lock and unlock
     mail boxes. These functions implement a NFS-safe locking mechanism.
     (It is ok if MUAs and MTAs don't link against liblockfile but use a
     *compatible* mechanism. Please compare the mechanisms very carefully!)

If emacs' current mechanism *is* compatible, then I could save some
hassle.

Thanks

-- 
Rob Browning <rlb@cs.utexas.edu>
PGP fingerprint = E8 0E 0D 04 F5 21 A0 94  53 2B 97 F5 D6 4E 39 30


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