Re: [RFC PATCH 3/6] smp: Run functions concurrently in smp_call_function_many()

[Nadav Amit]

> On May 27, 2019, at 2:15 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
>> +		/*
>> +		 * Choose the most efficient way to send an IPI. Note that the
>> +		 * number of CPUs might be zero due to concurrent changes to the
>> +		 * provided mask or cpu_online_mask.
>> +		 */
> 
> Since we have preemption disabled here, I don't think online mask can
> shrink, cpu-offline uses stop_machine().

Right. So Iâll update the comment, but IIUC the provided mask might still
change, so Iâll leave the rest of the comment and the code as is.

>> +		if (nr_cpus == 1)
>> +			arch_send_call_function_single_ipi(last_cpu);
>> +		else if (likely(nr_cpus > 1))
>> +			arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
>> +	}