| Date | Fri, 6 Apr 2007 19:34:07 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/8] Use process freezer for cpu-hotplug |
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* Nathan Lynch <ntl@pobox.com> wrote:
> > - raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu); > > + if (freeze_processes(FE_HOTPLUG_CPU)) { > > + thaw_processes(FE_HOTPLUG_CPU); > > + return -EBUSY; > > + } > > + > > If I'm understanding correctly, this will cause > > # echo 0 > /sys/devices/system/cpu/cpuX/online > > to sometimes fail, and userspace is expected to try again? This will > break existing applications. > > Perhaps drivers/base/cpu.c:store_online should retry as long as > cpu_up/down return -EBUSY. That would avoid a userspace-visible > interface change.
yeah. I'd even suggest a freeze_processes_nofail() API instead, that does this internally, without burdening the callsites. (and once the freezer becomes complete then freeze_processes_nofail() == freeze_processes())
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