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

On 11.02.20 17:46, Jan Beulich wrote:
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.

Ah, okay, then I misunderstood your intention.

I still think that this should be done not only in one place, but in a
more general fashion. I'd rather give up only after some time trying
(1 millisecond per default?) and apply the same scheme to all dumping

I can have a try for such a series if you agree on taking a more general


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