> On May 27, 2019, at 2:15 AM, Peter Zijlstra <pet...@infradead.org> 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 I’ll update the comment, but IIUC the provided mask might still change, so I’ll 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); >> + }
