Messages in this thread | | | Date | Wed, 5 Nov 2014 00:05:12 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: [RFC][PATCH 12/12 v3] x86/nmi: Perform a safe NMI stack trace on all CPUs |
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On Tue, 4 Nov 2014, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org> > > When trigger_all_cpu_backtrace() is called on x86, it will trigger an > NMI on each CPU and call show_regs(). But this can lead to a hard lock > up if the NMI comes in on another printk(). > > In order to avoid this, when the NMI triggers, it switches the printk > routine for that CPU to call a NMI safe printk function that records the > printk in a per_cpu seq_buf descriptor. After all NMIs have finished > recording its data, the trace_seqs are printed in a safe context. > > Link: http://lkml.kernel.org/p/20140619213952.360076309@goodmis.org > > Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
I've been running the whole machinery that used to trigger very quickly the complete hardlock of the machine (*) for the whole evening/night, and it's still running flawlessly.
Plus, as I said previously, I agree with the whole idea (given the general nastiness of the problem and given the fact this simply has to be fixed without pointless delays).
I.e FWIW
Tested-by: Jiri Kosina <jkosina@suse.cz> Acked-by: Jiri Kosina <jkosina@suse.cz>
for the whole series.
(*) heavy printk() workload (**) + sysrq-l in parallel (**) iptables logging every incoming packet + flood ping from another machine
Thanks,
-- Jiri Kosina SUSE Labs
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