Messages in this thread | | | Date | Thu, 24 Jul 2008 16:43:49 +0400 | From | Oleg Nesterov <> | Subject | Re: + pm-introduce-new-interfaces-schedule_work_on-and-queue_work_on.patch added to -mm tree |
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On 07/22, Gautham R Shenoy wrote: > > On Sat, Jul 12, 2008 at 08:21:49PM +0400, Oleg Nesterov wrote: > > > > So, this is used in http://bugzilla.kernel.org/attachment.cgi?id=16707 > > > > --- linux-2.6.orig/kernel/power/poweroff.c 2008-06-30 16:01:35.000000000 +0800 > > +++ linux-2.6/kernel/power/poweroff.c 2008-07-03 10:50:05.000000000 +0800 > > @@ -25,7 +25,8 @@ > > > > static void handle_poweroff(int key, struct tty_struct *tty) > > { > > - schedule_work(&poweroff_work); > > + /* run sysrq poweroff on boot cpu */ > > + schedule_work_on(first_cpu(cpu_online_map), &poweroff_work); > > } > > > > static struct sysrq_key_op sysrq_poweroff_op = { > > > > A couple of silly questions, I don't understand the low-level details. > > > > This patch (and kernel_power_off() afaics) assumes that the boot cpu > > can't be cpu_down()'ed. Is it true in general? For example, grep shows > > that arch/s390/kernel/smp.c:topology_init()->smp_add_present_cpu() > > sets ->hotpluggable = 1 for all present CPUs? > > I tried this on a Power system sometime back and I was able to > offline CPU0.
This means that
pm-schedule-sysrq-poweroff-on-boot-cpu.patch
is not 100% right. It is still possible to hang/deadlock if we race with cpu_down(first_cpu(cpu_online_map)).
The bug is mostly theoretical, but perhaps should be fixed anyway, handle_poweroff() can use kthread_run().
Oleg.
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