Messages in this thread | | | Date | Tue, 4 Nov 2014 18:41:02 -0500 | From | Steven Rostedt <> | Subject | Re: [RFC][PATCH 12/12 v3] x86/nmi: Perform a safe NMI stack trace on all CPUs |
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On Wed, 5 Nov 2014 00:05:12 +0100 (CET) Jiri Kosina <jkosina@suse.cz> wrote:
> 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.
Hmm, I need to update the change log to say seq_bufs instead of trace_seqs.
> > > > 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.
Thanks! I'll update the commits.
-- Steve
> > (*) heavy printk() workload (**) + sysrq-l in parallel > (**) iptables logging every incoming packet + flood ping from another > machine > > Thanks, >
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