linux-kernel - Re: [PATCH v2 04/11] sched: Simplify wake_up

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Message-ID: <YW7pOTqMT49cIsKz@hirez.programming.kicks-ass.net>
Date:   Tue, 19 Oct 2021 17:50:17 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Qian Cai <quic_qiancai@...cinc.com>
Cc:     gor@...ux.ibm.com, jpoimboe@...hat.com, jikos@...nel.org,
        mbenes@...e.cz, pmladek@...e.com, mingo@...nel.org,
        linux-kernel@...r.kernel.org, joe.lawrence@...hat.com,
        fweisbec@...il.com, tglx@...utronix.de, hca@...ux.ibm.com,
        svens@...ux.ibm.com, sumanthk@...ux.ibm.com,
        live-patching@...r.kernel.org, paulmck@...nel.org,
        rostedt@...dmis.org, x86@...nel.org
Subject: Re: [PATCH v2 04/11] sched: Simplify wake_up_*idle*()

On Tue, Oct 19, 2021 at 11:32:15AM -0400, Qian Cai wrote:
> 
> 
> On 10/19/2021 5:10 AM, Peter Zijlstra wrote:
> > Here, hows this then?
> > 
> > ---
> > diff --git a/kernel/smp.c b/kernel/smp.c
> > index ad0b68a3a3d3..61ddc7a3bafa 100644
> > --- a/kernel/smp.c
> > +++ b/kernel/smp.c
> > @@ -1170,14 +1170,12 @@ void wake_up_all_idle_cpus(void)
> >  {
> >  	int cpu;
> >  
> > -	cpus_read_lock();
> > -	for_each_online_cpu(cpu) {
> > -		if (cpu == raw_smp_processor_id())
> > -			continue;
> > -
> > -		wake_up_if_idle(cpu);
> > +	for_each_cpu(cpu) {
> > +		preempt_disable();
> > +		if (cpu != smp_processor_id() && cpu_online(cpu))
> > +			wake_up_if_idle(cpu);
> > +		preempt_enable();
> >  	}
> > -	cpus_read_unlock();
> >  }
> >  EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
> 
> This does not compile.
> 
> kernel/smp.c:1173:18: error: macro "for_each_cpu" requires 2 arguments, but only 1 given

Bah, for_each_possible_cpu(), lemme update the patch, I'm sure the
robots will scream bloody murder on that too.