linux-kernel - RE: [EXT] Re: [PATCH v2] tick/broadcast: Allow later registered device enter oneshot mode

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Date:   Wed, 31 Mar 2021 08:36:55 +0000
From:   "J.d. Yue" <jindong.yue@....com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        "fweisbec@...il.com" <fweisbec@...il.com>,
        "mingo@...nel.org" <mingo@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH v2] tick/broadcast: Allow later registered
 device enter oneshot mode


> -----Original Message-----
> From: Thomas Gleixner <tglx@...utronix.de>
> Sent: Wednesday, March 31, 2021 4:07 PM
> To: J.d. Yue <jindong.yue@....com>; fweisbec@...il.com; mingo@...nel.org
> Cc: linux-kernel@...r.kernel.org; J.d. Yue <jindong.yue@....com>
> Subject: [EXT] Re: [PATCH v2] tick/broadcast: Allow later registered device
> enter oneshot mode
> 
> Caution: EXT Email
> 
> On Wed, Mar 31 2021 at 09:10, Jindong Yue wrote:
> > --- a/kernel/time/tick-broadcast.c
> > +++ b/kernel/time/tick-broadcast.c
> > @@ -47,6 +47,7 @@ static inline void
> > tick_resume_broadcast_oneshot(struct clock_event_device *bc)  static
> > inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }  #
> > endif  #endif
> > +static void tick_handle_oneshot_broadcast(struct clock_event_device
> > +*dev);
> 
> Leftover ...

Removed in v3.

> 
> >  /*
> >   * Debugging: see timer_list.c
> > @@ -107,6 +108,19 @@ void tick_install_broadcast_device(struct
> clock_event_device *dev)
> >       tick_broadcast_device.evtdev = dev;
> >       if (!cpumask_empty(tick_broadcast_mask))
> >               tick_broadcast_start_periodic(dev);
> > +
> > +     if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
> > +             return;
> > +
> > +     /*
> > +      * If system already runs in oneshot mode, switch new registered
> 
> the system .... the newly registered
> 
> > +      * broadcast device to oneshot mode explicitly if possiable.
> 
> s/possible/possiable/
> 
> But the 'if possible' makes no sense here. The above check for
> CLOCK_EVT_FEAT_ONESHOT established that it _is_ possible. So just remove
> the 'if ...'.

I should be more careful ...
Please check v3 patch.

Thanks
Jindong

> 
> > +      */
> > +     if (tick_broadcast_oneshot_active()) {
> > +             tick_broadcast_switch_to_oneshot();
> > +             return;
> > +     }
> 
> Thanks,
> 
>         tglx