Re: automount subprocesses accumulate

[Ian Kent <raven@themaw.net>]

On Thu, 2015-09-10 at 16:43 +0200, Cyril B. wrote:
> Hello,
> 
> I've been using autofs for a long time to mount NFS servers under /nfs, 
> and recently started using it for mounting /home subdirectories as well 
> (which point on /nfs/).
> 
> Since I've started automounting /home, I have automount subprocesses 
> accumulating and never exiting:
> 
> root 1761264 0.0 0.0 205416 1478 ? Ssl 14:06 0:00 /usr/sbin/automount 
> --pid-file /var/run/autofs.pid
> root 1966587 0.0 0.0 209816 1564 ? S 14:45 0:00 \_ /usr/sbin/automount 
> --pid-file /var/run/autofs.pid
> root 2023507 0.0 0.0 209816 1652 ? S 15:00 0:00 \_ /usr/sbin/automount 
> --pid-file /var/run/autofs.pid
> root 2203212 0.0 0.0 215100 1900 ? S 15:45 0:00 \_ /usr/sbin/automount 
> --pid-file /var/run/autofs.pid

Yeah, that's odd.

> 
> My main automount was started at 14:06, and all subprocesses are stuck in a:
> 
> futex(0x56122035a5a0, FUTEX_WAIT_PRIVATE, 2, NULL
> 
> (same futex address for all of them).

Can you get a meaningful (that is with symbols, line numbers etc.) of
each of these processes and post it.

> 
> There are typically a few new subprocesses each hour. I've already seen 
> up to 20/25 subprocesses before I had to restart automount and kill them 
> manually.
> 
> I have a lot of users on this server, so automount is serving many 
> requests. Especially at round times (14:00, 14:15, 14:30, etc.), when 
> cron starts many user processes. According to automount debug logs, up 
> to 20 new home subdirectories can be mounted every second.

Yeah, that's quite a few, maybe your triggering a race with the thread
creation. I've spent a lot of time on that and thought it worked ok ...

Do you have reports from users of mounts hanging on access?

> 
> I'm using autofs 5.1.1 on Linux 4.1.4. My config:
> 
> /etc/auto.master:
> --
> /nfs program:/etc/auto.nfs
> /home program:/etc/auto.home
> --
> 
> /etc/auto.nfs is pretty standard, has been working fine for ages. It's 
> basically returning:
> 
> -fstype=nfs4,noatime,nosuid,_netdev,soft,intr,timeo=1000 $1:/
> 
> /etc/auto.home:
> --
> #!/bin/sh
> 
> if [ ! -h /var/home/$1 ]
> then
>    exit 1
> fi
> 
> echo -fstype=bind :$(readlink --no-newline /var/home/$1)
> --
> 
> So for instance, /var/home/foo would be a symlink pointing to 
> /nfs/serverX/foo.

So your bind mounting to an automounted nfs mount.
Not sure that's wise but probably should be ok.

I guess we need to look at the full debug log.
Can you post it somewhere or mail it to me privately please.

Ian

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