On 14/04/18 20:52, Jens Axboe wrote:
On 4/14/18 1:46 PM, Alan Jenkins wrote:
On 13/04/18 09:31, Johannes Thumshirn wrote:
Hi Alan,

On Thu, 2018-04-12 at 19:11 +0100, Alan Jenkins wrote:
# dd if=/dev/sda of=/dev/null iflag=direct & \
    while killall -SIGUSR1 dd; do sleep 0.1; done & \
    echo mem > /sys/power/state ; \
    sleep 5; killall dd  # stop after 5 seconds
Can you please also add a regression test to blktests[1] for this?

[1] https://github.com/osandov/blktests

Good question. It would be nice to promote this test.

Template looks like I need the commit (sha1) first.

I had some ideas about automating it, so I wrote a standalone (see
end).  I can automate the wakeup by using pm_test, but this is still a
system suspend test.  Unfortunately I don't think there's any
alternative. To give the most dire example

      # This test is non-destructive, but it exercises suspend in all drivers.
      # If your system has a problem with suspend, it might not wake up again.

So I'm not sure if it would be acceptable for the default set?

How useful is this going to be? Is there an expanded/full set of tests
that gets run somewhere?

If you can't guarantee it's going to be run somewhere, I'd worry the
cost/benefit  feels a little narrow :-(. There were one or two further
"interesting" details, and it might theoretically bitrot if it's not run
I run it, just last week we found two new bugs with it. I'm requiring
anyone that submits block patches to run the test suite, and also
working towards having it be part of the 0-day runs so it gets run
on posted patches automatically.

So yes, it's useful and it won't bitrot. Please do turn it into a blktests

Thanks, it's really great to have a test suite. I was specifically checking in on how we can include a system suspend test.

I've been thinking the suspend test could be opt-in test (e.g. ALLOW_PM_TEST=1), and then we have some infrastructure (you or 0-day runs) that does the opt-in.  Without knowing anything about the infrastructure, I didn't want to assume that would work.

I'm aware of one particular suspend issue; inside virt-manager VMs I see Linux crashing with a null pointer in qxl_drm_freeze.  A regression soon after I learned how to use VMs for suspend tests :-( , and it's been long enough that I suspect few people use it.

Partly what you saw me fishing for in the comments, is the idea of some kernel code allowing more direct testing of the queue freeze / preempt_only flag.  That might be better engineering, but I don't know where I could put it.


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