On Fri, Feb 5, 2021 at 11:22 AM Qais Yousef <qais.yousef@xxxxxxx> wrote: > > 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. Yup, the same idea here once Peter mentioned bringup_nonboot_cpus() and bringup_hibernate_cpu(). Best regards, Alexey
