linux-kernel - Re: [crash] Re: [PATCH 1/3] tracing/function-graph-tracer: introduce __notrace

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Date:	Fri, 12 Dec 2008 12:31:26 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Frédéric Weisbecker <fweisbec@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [crash] Re: [PATCH 1/3] tracing/function-graph-tracer:
	introduce __notrace_funcgraph to filter special functions


* Steven Rostedt <rostedt@...dmis.org> wrote:

> 
> On Tue, 9 Dec 2008, Fr?d?ric Weisbecker wrote:
> > 2008/12/9 Fr?d?ric Weisbecker <fweisbec@...il.com>:
> > 
> > 
> > I built this config on an smp x86-64 and booted several times (and
> > tested the function tracer manually) with and without the following
> > options:
> > 
> > initcall_debug apic=verbose sysrq_always_enabled ignore_loglevel
> > selinux=0 nmi_watchdog=2 idle=poll
> > 
> > And I can't reproduce this bug.... That might be a very nasty race condition...
> 
> Neither can I :-(
> 
> Ingo, is this on the box that stresses NMIs?

yes. You could try to inject even more NMIs than i normally do, 
artificially, by picking up tip/master and running KernelTop with a 
100,000 cycles IRQ interval:

    http://redhat.com/~mingo/perfcounters/kerneltop.c

run it like this:

    ./kerneltop -c 100000

and run an infinite loop per process:

    while :; do :; done &

to get the NMIs going intensely:

------------------------------------------------------------------------------
 KernelTop:  115437 irqs/sec  [NMI, 100000 cycles],  (all, 16 CPUs)
------------------------------------------------------------------------------

             events         RIP          kernel function
  ______     ______   ________________   _______________

           81224.00 - ffffffffff6001a4 : vread_hpet
            3119.00 - ffffffff8027cf99 : perf_read
            2484.00 - ffffffff802227d5 : read_hpet
            1157.00 - ffffffff8056b69a : mutex_lock
            1041.00 - ffffffffff600000 : vgettimeofday
             986.00 - ffffffff80333db5 : avc_has_perm_noaudit
             896.00 - ffffffff8026be2d : audit_syscall_exit
             653.00 - ffffffff8056c8f5 : _spin_lock
             577.00 - ffffffff802ecd14 : dnotify_parent
             528.00 - ffffffff8033679c : file_has_perm
             489.00 - ffffffff802bc060 : dput
             470.00 - ffffffff8026c366 : audit_syscall_entry


	Ingo
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