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Re: [Nmh-workers] Locking In Scripts and nmh Locking

From: norm
Subject: Re: [Nmh-workers] Locking In Scripts and nmh Locking
Date: Sat, 28 Apr 2012 05:33:00 -0700

address@hidden writes:
>Content-Type: text/plain; charset=us-ascii
>On Fri, 27 Apr 2012 13:48:19 -0700, address@hidden said:
>>      command is not executed until no other 'mhlock -all' is running, and 
>> until
>>      no relevant nmh program is running. While command is running no other
>>      mhlock -all runs nor does any relevant nmh program run.
>If 'command' is a shell script that ends up inadvertently calling something
>that calls mhlock itself, you just deadlocked.  And blindly changing the
>call inside the script to have a --noblock semantic may not be right either,
>as then it would be unsafe to run the script standalone without an mhlock

You are right!

How about an environment variable, say NMH_LOCK. When NMH_LOCK is set,
mhlock -all would ignore locking. Otherwise mhlock -all would set it before
executing command, but after obtaining the lock, and unset it when command
exits, but before relinquishing the lock.

>Locking is hard

Sure is. But that doesn't mean that it should be ignored.

    Norman Shapiro
    798 Barron Avenue
    Palo Alto CA 94306-3109
    (650) 565-8215

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