Messages in this thread | | | Date | Fri, 3 Feb 2012 17:57:40 -0500 | From | Don Zickus <> | Subject | Re: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop() |
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On Fri, Feb 03, 2012 at 10:32:31PM +0000, Luck, Tony wrote: > > What if we send the REBOOT_IPI first and let it block for up to a second. > > Most code paths that are done with spin_locks will use > > spin_lock_irqrestore. As soon as the interrupts are re-enabled the > > REBOOT_IPI comes in and takes the processor. If after a second the cpu > > still is blocking interrupts, just use the NMI as a big hammer to shut it > > down. > > This looks good - it certainly deals with my "if we just let them run > a bit, they'd release the locks" quibble. One second sounds very > generous - but I'm not going to bikeshed that (so long as it is a total > of one second - not one second per cpu). So the pseudo-code is:
This is how the stop_cpus is implemented on x86 and the one second comes from there
arch/x86/kernel/smp.c::native_irq_stop_other_cpus and native_nmi_stop_other_cpus
> > send_reboot_ipi_to_everyone_else() > > wait_1_second() > > for_each_cpu_that_didnt_respond_to_reboot_ipi { > hit_that_cpu_with_NMI() > } > > Perhaps a notification printk() if we had to use the NMI hammer?
Yes.
Again this is for x86, but I guess that is our common case with pstore.
Cheers, Don
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