Re: [Xen-devel] [PATCH v5 08/19] xen/sched: make vcpu_wake() and vcpu_sleep() core scheduling aware

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Mon, 2019-09-30 at 07:21 +0200, Juergen Gross wrote:
> vcpu_wake() and vcpu_sleep() need to be made core scheduling aware:
> they might need to switch a single vcpu of an already scheduled unit
> between running and not running.
> 
> Especially when vcpu_sleep() for a vcpu is being called by a vcpu of
> the same scheduling unit special care must be taken in order to avoid
> a deadlock: the vcpu to be put asleep must be forced through a
> context switch without doing so for the calling vcpu. For this
> purpose add a vcpu flag handled in sched_slave() and in
> sched_wait_rendezvous_in() allowing a vcpu of the currently running
> unit to switch state at a higher priority than a normal schedule
> event.
> 
> Use the same mechanism when waking up a vcpu of a currently active
> unit.
> 
> While at it make vcpu_sleep_nosync_locked() static as it is used in
> schedule.c only.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
> RFC V2: add vcpu_sleep() handling and force_context_switch flag
> V2: fix runstate change in sched_force_context_switch()
> V4:
> - use unit_scheduler() where appropriate (Jan Beulich)
> - make cpu parameter unsigned int (Jan Beulich)
> - comments (Jan Beulich)
> - use true instead 1 for setting bool (Jan Beulich)
> - const parameter (Jan Beulich)
> V5:
> - add comments (Dario Faggioli)
>
Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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