Re: [Xen-devel] [PATCH v2] xen/sched: add some diagnostic info in the run queue keyhandler

[Jan Beulich <jbeulich@xxxxxxxx>]

On 11.02.2020 14:10, Jürgen Groß wrote:
> On 11.02.20 14:01, Jan Beulich wrote:
>> On 11.02.2020 13:27, Juergen Gross wrote:
>>> When dumping the run queue information add some more data regarding
>>> current and (if known) previous vcpu for each physical cpu.
>>>
>>> With core scheduling activated the printed data will be e.g.:
>>>
>>> (XEN) CPUs info:
>>> (XEN) CPU[00] current=d[IDLE]v0, curr=d[IDLE]v0, prev=NULL
>>> (XEN) CPU[01] current=d[IDLE]v1
>>> (XEN) CPU[02] current=d[IDLE]v2, curr=d[IDLE]v2, prev=NULL
>>> (XEN) CPU[03] current=d[IDLE]v3
>>>
>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>> ---
>>> V2: add proper locking
>>
>> "Proper" is ambiguous in the context of dumping functions. In a
>> number of places we use try-lock, to avoid the dumping hanging
>> on something else monopolizing the lock. I'd like to suggest to
>> do so here, too.
> 
> All the scheduler related dumping functions are using the "real" locks.
> So using trylock in this single case wouldn't help at all. Additionally
> using trylock only would make a crash during dumping the data more
> probable, so I'm not sure we want that.

Why would it make a crash more likely? If you can't get the lock,
you'd simply skip dumping.

Jan

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