Messages in this thread | | | Subject | Re: + pm-introduce-new-interfaces-schedule_work_on-and-queue_work_on.patch added to -mm tree | From | Zhang Rui <> | Date | Fri, 25 Jul 2008 09:17:29 +0800 |
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On Thu, 2008-07-24 at 20:43 +0800, Oleg Nesterov wrote: > 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)).
Yes, you're right. But then should we fix disable_nonboot_cpus as well?
int disable_nonboot_cpus(void) { first_cpu = first_cpu(cpu_online_map); ... for_each_online_cpu(cpu) { if (cpu == first_cpu) continue; error = _cpu_down(cpu, 1); ... } ... }
thanks, rui
> The bug is mostly theoretical, but perhaps should be fixed anyway, > handle_poweroff() can use kthread_run(). >
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