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

[Jürgen Groß <jgross@xxxxxxxx>]

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.

Instead of unconditionally using trylock in dumping functions I could
imagine to have a "dumplock" using proper locking by default which can
be toggled to trylock in case it is needed (or maybe automatically by
adding a timeout to the dumplock variant).


Juergen

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