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

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Date:   Tue, 19 Oct 2021 15:22:43 -0400
From:   Qian Cai <quic_qiancai@...cinc.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 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.