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Re: [Xen-devel] [PATCH 3/8] xen/sched: don't use irqsave locks in dumping functions

On Wed, 2020-02-19 at 16:02 +0100, Jürgen Groß wrote:
> On 19.02.20 15:27, Jan Beulich wrote:
> > On 13.02.2020 13:54, Juergen Gross wrote:
> > > All dumping functions invoked by the "runq" keyhandler are called
> > > with
> > > disabled interrupts,
> > 
> > Is this actually needed for anything? It means not servicing
> > interrupts for perhaps an extended period of time. Debug keys
> > aren't promised to be non-intrusive, but they also shouldn't
> > be more intrusive than really needed. Wouldn't it therefore
> > be better to keep locking as it is now, and instead make sure
> > interrupts get turned off elsewhere (if needed) for much
> > shorter periods of time?
> Indeed this is the better option. I just checked the code and
> think blindly turning interrupts off is not needed.
Well, yes... Assuming you are referring to the IRQ being disabled in
cpupool.c:dump_runq(), my impression is that we can get rid of that,
and leave the sched-specific code (more or less) as it is (for the sake
of runqueue lock irq-safety).

Dario Faggioli, Ph.D
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)

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