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Re: [Nmh-workers] Pasing stdin to "inc -file" ?


From: David Levine
Subject: Re: [Nmh-workers] Pasing stdin to "inc -file" ?
Date: Mon, 18 Feb 2013 20:53:35 -0500

Valdis wrote:

> And the exact gotcha involved, from 'nman rcvstore':
> 
> BUGS
>        If you use the "Unseen-Sequence" profile entry, rcvstore
>        could try to update the context while another nmh process is
>        also trying to do so.  This can cause the context to become
>        corrupted.  To avoid this, do not use rcvstore if you use the
>        "Unseen-Sequence" profile entry.

I removed that notice from the man page after 1.5 went out.
However, I shouldn't have.  Ken added locking to the context
and sequences files nearly a decade ago.  That addresses
file mangling during write, but not possible interaction with
other nmh processes.

> What it doesn't mention is that the resulting train wreck
> can mangle other sequences in the .mh_seq file as well.

There shouldn't be concurrent writes of context and
sequences files.  So that kind of mangling shouldn't happen
any more.

> Also, should we change that text to say "do not use
> rcvstore without an external locking mechanism'?  It's
> perfectly save to use it from procmail with unseen
> sequences as long as procmail does the locking for you, so
> there's no need to scare off users.

I'll restore the warning and add mention of an external
locking mechanism if Unseen-Sequence is used.  However, I
wouldn't call it perfectly safe, given the possible
interaction with other nmh processes that it mentions.

David



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