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SubjectRe: [PATCH v4 14/16] timer: Implement the hierarchical pull model
On Wed, 9 Nov 2022, Frederic Weisbecker wrote:

> On Fri, Nov 04, 2022 at 03:57:35PM +0100, Anna-Maria Behnsen wrote:
> > diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> > index f8b2065df79b..214397d84747 100644
> > --- a/kernel/time/timer.c
> > +++ b/kernel/time/timer.c
> > @@ -53,6 +53,7 @@
> > #include <asm/io.h>
> >
> > #include "tick-internal.h"
> > +#include "timer_migration.h"
> >
> > #define CREATE_TRACE_POINTS
> > #include <trace/events/timer.h>
> > @@ -592,10 +593,13 @@ trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
> >
> > /*
> > * We might have to IPI the remote CPU if the base is idle and the
> > - * timer is not deferrable. If the other CPU is on the way to idle
> > - * then it can't set base->is_idle as we hold the base lock:
> > + * timer is pinned. If it is a non pinned timer, it is only queued
> > + * on the remote CPU, when timer was running during queueing. Then
> > + * everything is handled by remote CPU anyway.
> > + * on the way to idle then it can't set base->is_idle as we hold
> > + * the base lock:
> > */
> > - if (base->is_idle)
> > + if (base->is_idle && timer->flags & TIMER_PINNED)
> > wake_up_nohz_cpu(base->cpu);
>
> I'm probably missing something but, shouldn't there be a call to
> tmigr_new_timer() on the target to handle the new non-pinned timer?
>

We need to keep the original way right now. This TIMER_PINNED condition is
valid only when enqueue on local CPU is in place.

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