Re: [linux-pm] [RFC 07/10] powermac: support G5 CPU hotplug
From: Pavel Machek <hidden>
Date: 2007-02-06 12:42:12
Also in:
linux-pm
Hi!
This patch allows "hotplugging" of CPUs on G5 machines. CPUs that are disabled are put into an idle loop with interrupts hard-disabled, to wake them up again we kick them just like when bringing them up. Maybe there's some way to actually turn off those CPUs even more? Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
quoted hunk ↗ jump to hunk
--- mb-wireless.orig/arch/powerpc/kernel/smp.c 2007-02-05 16:07:09.274524763 +0100 +++ mb-wireless/arch/powerpc/kernel/smp.c 2007-02-05 18:15:51.114524763 +0100@@ -558,6 +558,11 @@ int __devinit start_secondary(void *unus local_irq_enable(); + /* it seems to be possible that we died from within + * an interrupt ... reset the in-irq counts */ + task_thread_info(paca[cpu].__current)->preempt_count &= + ~(SOFTIRQ_MASK|HARDIRQ_MASK); + cpu_idle(); return 0;
This is quite a nasty hack. Are you sure? I've seen similar weirdness on pc, and it was caused by swsusp-copying-code using FPU and incrementing preempt_count... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html