/proc/locks debug helper (cyrus deadlock tracing)

Bron Gondwana brong at fastmail.fm
Thu Aug 6 17:48:45 EDT 2015

Interesting.  We definitely need to get this right.  Though I'm about to reply to your other email...

On Fri, Jul 24, 2015, at 17:15, Thomas Jarosch wrote:
> Hello,
> attached is a small helper script that parses
> the output of /proc/locks. The file format is described here:
> https://www.centos.org/docs/5/html/5.2/Deployment_Guide/s2-proc-locks.html
> It resolves the program name from the pid number and also
> resolves the filename from the inode number.
> That way we can see which program is currently holding an exclusive
> lock on a file and which program is waiting for the lock to come free.
> This would probably also show an ABBA deadlock,
> though I didn't encounter one in the wild yet.
> You may need to adapt the paths in the "config" section of the program
> to your local setup. 
> The layout of /proc/locks might change depending on the kernel version,
> I've tested it with 3.14.x. The script works with python 3.x and 2.7.
> When you call it with "--shown-non-waiting", it will show you
> which mailboxes currently hold a READ lock. The program does a bit
> of filtering to keep the noise ratio down, so be sure to check
> out the other options described in "--help".
> Hopefully this helps others if they should run into a deadlock situation.
> Cheers,
> Thomas
> Email had 1 attachment:
> + parse_proc_locks.py
>   4k (text/x-python)

  Bron Gondwana
  brong at fastmail.fm

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