Messages in this thread | | | Date | Wed, 9 Jul 2008 00:02:02 +0900 | From | "Akinobu Mita" <> | Subject | Re: [PATCH 2/3] stop_machine: simplify |
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2008/7/8 Rusty Russell <rusty@rustcorp.com.au>: > On Tuesday 08 July 2008 21:44:40 Akinobu Mita wrote: >> I found a small possible cleanup in this patch. > > Well spotted! I think this cleanup is actually orthogonal to my patch, > so best served as a separate patch, how's this?
Actually the cpu_online() check was necessary before appling this stop_machine: simplify patch.
With old __stop_machine_run(), __stop_machine_run() could succeed (return !IS_ERR(p) value) even if take_cpu_down() returned non-zero value. The return value of take_cpu_down() was obtained through kthread_stop().
> === > Hotplug CPU: don't check cpu_online after take_cpu_down
So it seems that folding this patch into stop_machine: simplify patch is more appropriate.
> Akinobu points out that if take_cpu_down() succeeds, the cpu must be offline > (otherwise we're in deep trouble anyway. > > Remove the cpu_online() check, and put a BUG_ON(). > > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> > Cc: "Akinobu Mita" <akinobu.mita@gmail.com> > > diff -r 805a2e5e68dd kernel/cpu.c > --- a/kernel/cpu.c Tue Jul 08 23:04:48 2008 +1000 > +++ b/kernel/cpu.c Tue Jul 08 23:07:43 2008 +1000 > @@ -226,8 +226,7 @@ static int __ref _cpu_down(unsigned int > set_cpus_allowed_ptr(current, &tmp); > > err = __stop_machine_run(take_cpu_down, &tcd_param, cpu); > - > - if (err || cpu_online(cpu)) { > + if (err) { > /* CPU didn't die: tell everyone. Can't complain. */ > if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod, > hcpu) == NOTIFY_BAD) > @@ -235,6 +234,7 @@ static int __ref _cpu_down(unsigned int > > goto out_allowed; > } > + BUG_ON(cpu_online(cpu)); > > /* Wait for it to sleep (leaving idle task). */ > while (!idle_cpu(cpu)) >
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