mount/umount in autofs keeps locking up (is it fam?)

[Paul Raines]

We have a rather large autofs setup at our site with four different
maps/mountpoints and one them being quite large with >1000 entries.  
However, on any one box rarely will over 20 mounts be used at once.

We recently installed a FC2 box and everything works fine until somebody
starts up a KDE application.  Soon after that we will notice automounting
stops working and several NFS mounts are unresponsive.  Doing a 'ps'
shows several 'mount' and 'umount' process hung in the 'D' state.
Looking at the kernel log I find:

Badness in interruptible_sleep_on at kernel/sched.c:1927
Call Trace:
 [<0229fe72>] interruptible_sleep_on+0x5a/0xc6
 [<0211b419>] default_wake_function+0x0/0xc
 [<021783d1>] proc_pid_lookup+0x199/0x1e1
 [<f889b4f9>] autofs4_wait+0x1fe/0x25e [autofs4]
 [<f889a576>] try_to_fill_dentry+0x39/0x100 [autofs4]
 [<02159950>] do_lookup+0x54/0x72
 [<02159f70>] link_path_walk+0x602/0x7d0
 [<021616a7>] dput+0x18/0x16c
 [<0215c557>] vfs_follow_link+0x114/0x177
 [<02159d42>] link_path_walk+0x3d4/0x7d0
 [<021616a7>] dput+0x18/0x16c
 [<0215c557>] vfs_follow_link+0x114/0x177
 [<02159d42>] link_path_walk+0x3d4/0x7d0
 [<0215a42b>] path_lookup+0x13f/0x16f
 [<0215a567>] __user_walk+0x21/0x51
 [<02156177>] vfs_stat+0x14/0x3a
 [<021566e9>] sys_stat64+0xf/0x23

This message if followed by some nfs server timeouts and then some
other identical "Badness" messages depending on how long i wait
to reboot.

The thing with KDE that I suspect as the most likely culprit is
that KDE starts the 'fam' process which does filesystem monitoring.
I don't think that 'fam' is actually a critically needed process
so I am removing it to do a test.

Of course the bug is not necessarily with 'fam', but could be 
in the kernel or autofs.  Just 'fam' is what I suspect triggers it.

-- 
---------------------------------------------------------------
Paul Raines                   email: raines at nmr.mgh.harvard.edu
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging
149 (2301) 13th Street        Charlestown, MA 02129	USA