Re: DDF test fails if default udev rules are active

[NeilBrown <neilb@suse.de>]

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On Wed, 27 Mar 2013 21:44:21 +0100 Martin Wilck <mwilck@arcor.de> wrote:

> Hi Neil,
> 
> with my latest patch set, the DDF test case (10-ddf-create) succeeds
> reliably for me, with one caveat: It works only if I disable the rule
> that runs "mdadm -I" on a newly discovered container. On my system
> (Centos 6.3) it is in /lib/udev/65-md-incremental.rules, and the rule is
> 
> SUBSYSTEM="block", ACTION="add|change", KERNEL="md*", \
>   ENV{MD_LEVEL}=="container", RUN+="/sbin/mdadm -I $env{DEVNAME}"
> 
> The reason is that the DDF test case runs mdadm -Asc after writing the
> conf file defining the container and 3 arrays.
> 
> mdadm -Asc will first create the container. When it starts tries to
> create the member arrays, these have already been started by the udev
> rule above, causing the assembly to fail with the error message "member
> /dev/md127/1 in /dev/md127 is already assembled".
> 
> I have done my testing with the above udev rule commented out, and all
> goes fine. But I am not sure if "mdadm -Asc /var/tmp/mdadm.conf" failing
> indicates a problem with the DDF code, or if it's really just a problem
> with the test case. Personally, I'd rather have a test case that
> succeeds by default on a system with standard configuration (which means
> the above udev rule should be active).
> 
> What do you think?
> Martin

Hi Martin,
 I think this is a real issue that has occasionally annoyed me a bit but
 never enough to make me seriously address it - so thanks for raising it.

 I generally would like the tests to run without any interference from udev,
 though I certainly see the value of testing in a "standard config" context
 too.

 Fortunately it appears to be easy to address.
   udevadm control --stop-exec-queue
 will pause udev, and
   udevadm control --start-exec-queue
 will cause udev to resume.

 So I suggest that we change the 'test' script to run:

    udevadm settle; udevadm control --stop-exec-queue

 before running each test script, and

    udevadm control --start-exec-queue

 after the script.
 Then if a script wants to run in "standard" context, it could simply put
    udevadm control --start-exec-queue
 at the top.  The default would be to disable udev which is what most scripts
 expect.

 Can you try that?

Thanks,
NeilBrown


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