Re: [Xen-devel] [xen-unstable test] 113562: regressions - FAIL

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 09/18/2017 11:46 AM, Roger Pau Monné wrote:
> On Mon, Sep 18, 2017 at 11:15:03AM +0100, George Dunlap wrote:
>> On 09/18/2017 10:45 AM, Roger Pau Monné wrote:
>>> On Mon, Sep 18, 2017 at 10:37:58AM +0100, Wei Liu wrote:
>>>> On Mon, Sep 18, 2017 at 08:36:03AM +0000, osstest service owner wrote:
>>>>> flight 113562 xen-unstable real [real]
>>>>> http://logs.test-lab.xenproject.org/osstest/logs/113562/
>>>>>
>>>>> Regressions :-(
>>>>>
>>>>> Tests which did not succeed and are blocking,
>>>>> including tests which could not be run:
>>>>>  test-amd64-amd64-xl-credit2  15 guest-saverestore        fail REGR. vs. 
>>>>> 113387
>>>>
>>>> There appears to be a bug:
>>>>
>>>> http://logs.test-lab.xenproject.org/osstest/logs/113562/test-amd64-amd64-xl-credit2/serial-godello0.log
>>>>
>>>> Sep 18 01:14:28.803062 (XEN) Xen BUG at spinlock.c:47
>>>
>>> Seem to be caused because budget_lock is sometimes locked with irqsave
>>> while others not.
>>
>> Just wondering where you're getting the budget lock from?  The call
>> stack in that link makes it look like it's the RCU clean-up triggering a
>> domain destroy.  (Haven't looked deeper into the specific line numbers.)
> 
> Just skimmed over the commit and jumped into conclusions too fast. As
> you mention later the issue is calling xfree with interrupts disabled
> in csched2_free_domdata.
> 
> I would rather prefer budget_lock to be always locked with the
> irqsave/restore variant to make what you mention above more obvious,
> but that's just a question of taste.

I *think* at some point in the past we had a discussion about this and
someone (perhaps Jan?) said if we always know the irqs are disabled we
shouldn't call the _irqsave() version, to save cpu cycles.

Personally I think the ASSERT()s are clear enough to people familiar
with the scheduling code.

 -George

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