Bug#658028: usbmount: Udev should not wait for mounting

[Hagen Fuchs]

Package: usbmount
Followup-For: Bug #658028

This is indeed a very valid concern (not that I have been affected
personally).  Quite a few scripts in /lib/udev/rules.d seem to be doing
things that might take a while or even hang.  I'm surprised, honestly.

In any case, I imagine usbmount's udev compliance could be trivially
ensured: make 'usbmount' a wrapper that calls, say, usbmount.real proper
with all the banalities, insecurities, hopes and despair that comes with
it.

I created a branch of the alioth upstream sources that implements
precisely this change,

https://github.com/hfuchs/usbmount/tree/hfuchs.658028

and also renames usbmount.rules - 90-usbmount.rules because it seemed
proper (all of the other rule scripts start with some ordering number,
only usbmount stood out :).

How about it?

-Hagen


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Bug#658028: usbmount: Udev should not wait for mounting

[Frédéric Brière]

On Mon, Jan 30, 2012 at 02:53:28PM -0600, Karl O. Pinc wrote:
 Usbmount is run directly from the udev rule engine and the rule engine
 must wait for usbmount to complete.  This is wrong.
 
 If usbmount is not going to run as a daemon I imagine it should at
 least detach before doing any work.

Indeed.  Due to this, combined with #377548, my bootup sequence includes
a 30-second pause with nothing happening except udev patiently waiting
for usbmount to complete.


-- 
I was attacked by dselect as a small child and have since avoided
debian.
-- Andrew Morton


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Bug#658028: usbmount: Udev should not wait for mounting

[Karl O. Pinc]

Package: usbmount
Version: 0.0.21
Severity: important

Hello,

Usbmount is run directly from the udev rule engine and the rule engine
must wait for usbmount to complete.  This is wrong.

If usbmount is not going to run as a daemon I imagine it should at
least detach before doing any work.

From the developers of udev:
http://www.spinics.net/lists/hotplug/msg05325.html
-snip-

Udev's rule engine is not the right place to hookup mounting of
arbitrary filesystems, or configure non-trivial network settings like
DHCP, or start system daemons, or run any other programs that runs for
an unpredictable amount of time. Udev rules should only be used to
identify or initially configure hardware, but never to execute system
management jobs or things that involve policy or need error handling
like filesystem checking or mounting. Running such programs from udev
rules will block related events, and might render the entire system
unusable. To ensure timely event execution, udev forcefully kills all
programs it has executed from rules, and which take longer than 30 or
60 seconds to finish, and mounting and checking disks can take much
longer than that.

Udev can send events to services which can act on device changes
though. An auto-mounter service can listen to block device events and
take the appropriate actions, such a service will not block udev's
operations for an unpredictable time. Udisks and systemd for example
work like that.

Mounting filesystems is just not simple enough to do that in udev, you
need a real service to do that properly. Udev rules are just not the
right tool for the job, and very likely never will be.
-snip-

-- System Information:
Debian Release: 6.0.3
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.32-5-686 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages usbmount depends on:
ii  lockfile-progs0.1.15 Programs for locking and unlocking
ii  udev  164-3  /dev/ and hotplug management daemo
ii  util-linux2.17.2-9   Miscellaneous system utilities

Versions of packages usbmount recommends:
ii  pmount0.9.23-1   mount removable devices as normal 

usbmount suggests no packages.

-- no debconf information



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