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Subject: Re: [PATCH v2 04/11] sched: Simplify wake_up_*idle*()
To:     Peter Zijlstra <peterz@infradead.org>
CC:     <gor@linux.ibm.com>, <jpoimboe@redhat.com>, <jikos@kernel.org>,
        <mbenes@suse.cz>, <pmladek@suse.com>, <mingo@kernel.org>,
        <linux-kernel@vger.kernel.org>, <joe.lawrence@redhat.com>,
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        <live-patching@vger.kernel.org>, <paulmck@kernel.org>,
        <rostedt@goodmis.org>, <x86@kernel.org>
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From:   Qian Cai <quic_qiancai@quicinc.com>
Message-ID: <80919fdc-0f36-2f8a-627d-c1a97f1830fb@quicinc.com>
Date:   Tue, 19 Oct 2021 15:22:43 -0400
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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.