linux-kernel - Re: [PATCH 2/6] tracing: increase size of number of possible events

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Date:	Sun, 26 Apr 2009 09:44:04 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Li Zefan <lizf@...fujitsu.com>
cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 2/6] tracing: increase size of number of possible
 events


Hi Li,


On Sun, 26 Apr 2009, Li Zefan wrote:

> Steven Rostedt wrote:
> > On Fri, 24 Apr 2009, Steven Rostedt wrote:
> > 
> >> On Fri, 24 Apr 2009, Li Zefan wrote:
> >>> console 1:
> >>>  # cat /debug/tracing/trace_pipe
> >>>
> >>> console 2:
> >>> while (1) {
> >>> 	insmod trace-events-sample.ko
> >>> 	echo foo_bar > /debug/tracing/set_event
> >>> 	rmmod trace-events-sample.ko
> >>> }
> >>>
> >>> I got this immediately:
> >>>
> >>> BUG: unable to handle kernel NULL pointer dereference at 0000006f
> >>> IP: [<c05210f3>] bstr_printf+0x2ce/0x302
> >>> ...
> >>> Call Trace:
> >>>  [<c0476d12>] ? trace_seq_bprintf+0x28/0x41
> >>>  [<c0477569>] ? trace_bprint_print+0x58/0x6c
> >>>  [<c0472ffc>] ? print_trace_line+0x2c5/0x2df
> >>>  [<c0428a41>] ? sub_preempt_count+0x85/0xa0
> >>>  [<c04758cf>] ? tracing_read_pipe+0x118/0x191
> >>>  [<c04757b7>] ? tracing_read_pipe+0x0/0x191
> >>>  [<c04b09f9>] ? vfs_read+0x8f/0x136
> >>>  [<c04b0da3>] ? sys_read+0x40/0x65
> >>>  [<c0402a68>] ? sysenter_do_call+0x12/0x36
> >>>
> >>> (We can even get other crashes..)
> >>>
> >> Can you send me your full bootlog and config. I'm not able to reproduce 
> >> this.
> > 
> > And the SHA1 of the HEAD of the git repo you are using.
> > 
> > Thanks,
> > 
> 
> the HEAD: 9ce5424d75e56891905b77d1589924765e62059a + this patch
> 
> (I commented out "hi" from the sample module)

I found that commenting out the "hi" too helped in causing races.

> 
> I think it's because "type" is wrapped back to 0. I changed the test script
> like this:
> 
> while (foo_bar.id < 65536)
> {
> 	insmod trace-events-sample.ko
> 	rmmod trace-events-sample.ko
> }
> 
> for ((; ;))
> {
>         insmod /home/lizf/linux-2.6-tip/samples/trace_events/*.ko
>         echo trace-events-sample:foo_bar > /mnt/tracing/set_event
>         sleep 1
>         cat /mnt/tracing/trace
>         rmmod /home/lizf/linux-2.6-tip/samples/trace_events/*.ko
> }
> 

Could you try my git repo with my latest changes?

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git

 branch: rfc/debugfs

Thanks,

-- Steve

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