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

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Date:   Tue, 19 Oct 2021 22:27:55 +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 03:22:43PM -0400, Qian Cai wrote:
> 
> 
> On 10/19/21 11:50 AM, Peter Zijlstra wrote:
> >>> 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.
> 
> This survived the regression tests here.

Thanks!