[Dovecot] pop3_lock_session question

[Timo Sirainen]

On Wed, 2009-02-04 at 14:58 -0500, Timo Sirainen wrote:
> On Wed, 2009-02-04 at 14:51 -0500, Alan Ferrency wrote:
> > One problem which might be making this worse than it needs to be, is
> > the fact that mbox_lock_flock in mbox-lock.c is not using a blocking
> > flock(); instead, it's polling for a non-blocking lock.  This technique
> > can cause lock starvation, if another process is dropping the lock and
> > picking it back up again frequently: other processes will only see the
> > lock as being available if they happen to poll for the lock at just
> > the right instant.
> > 
> > A better technique to use here, if it's adequately cross-platform,
> > would be to set an alarm() for the max_wait_time, and use a blocking
> > flock().  If the alarm times out and you don't have a lock, it's a
> > timeout.  In the meantime, you're guaranteed to eventually get the
> > lock, if it is dropped.
> 
> That's what Dovecot does elsewhere. I don't really know why I'm using
> non-blocking flock() calls. 

I think it's because originally Dovecot was ignoring SIGALRMs which also
caused alarm()s not to work right. But I stopped doing that years ago.

> I guess I should fix that.

Added fix to v1.2 only:
http://hg.dovecot.org/dovecot-1.2/rev/8cca2bf6ab76
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: This is a digitally signed message part
Url : http://dovecot.org/pipermail/dovecot/attachments/20090204/07450129/attachment.bin