Messages in this thread Patch in this message | | | Date | Sat, 12 Jul 2008 20:21:49 +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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(Gautham cc'ed)
On 07/11, Andrew Morton wrote: > > Subject: pm: introduce new interfaces schedule_work_on() and queue_work_on() > From: Zhang Rui <rui.zhang@intel.com> > > This interface allows adding a job on a specific cpu. > > Although a work struct on a cpu will be scheduled to other cpu if the cpu > dies, there is a recursion if a work task tries to offline the cpu it's > running on. we need to schedule the task to a specific cpu in this case. > http://bugzilla.kernel.org/show_bug.cgi?id=10897
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?
Another question. I can't understand why first_cpu(cpu_online_map) is always the boot CPU on every arch. IOW, shouldn't boot_cpu_init() set some "boot_cpu = smp_processor_id()" which should be use instead of first_cpu(cpu_online_map) ?
Thanks,
Oleg.
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