On 02/04/21 10:46, Peter Zijlstra wrote: > On Thu, Feb 04, 2021 at 01:01:57AM +0000, Alexey Klimov wrote: > > @@ -1281,6 +1282,11 @@ static int cpu_up(unsigned int cpu, enum cpuhp_state target) > > err = _cpu_up(cpu, 0, target); > > out: > > cpu_maps_update_done(); > > + > > + /* To avoid out of line uevent */ > > + if (!err) > > + cpuset_wait_for_hotplug(); > > + > > return err; > > } > > > > > @@ -2071,14 +2075,18 @@ static void cpuhp_online_cpu_device(unsigned int cpu) > > struct device *dev = get_cpu_device(cpu); > > > > dev->offline = false; > > - /* Tell user space about the state change */ > > - kobject_uevent(&dev->kobj, KOBJ_ONLINE); > > } > > > > One concequence of this is that you'll now get a bunch of notifications > across things like suspend/hybernate. And the resume latency will incur 5-30ms * nr_cpu_ids. Since you just care about device_online(), isn't cpu_device_up() a better place for the wait? This function is special helper for device_online(), leaving suspend/resume and kexec paths free from having to do this unnecessary wait. Thanks -- Qais Yousef
