linux-kernel - Re: [PATCH 2/3] Add tracing_off_event() calls to BUG() and WARN() paths

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Message-ID: <m2i40ec3ea41004152113kf902102ex31e35c1bff5060ab@mail.gmail.com>
Date:	Thu, 15 Apr 2010 21:13:25 -0700
From:	Chase Douglas <chase.douglas@...onical.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Randy Dunlap <randy.dunlap@...cle.com>
Subject: Re: [PATCH 2/3] Add tracing_off_event() calls to BUG() and WARN() 
	paths

On Thu, Apr 15, 2010 at 4:15 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
> On Thu, Apr 15, 2010 at 02:49:05PM -0700, Chase Douglas wrote:
>> On Thu, Apr 15, 2010 at 1:57 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
>> > On Wed, Apr 14, 2010 at 12:20:15PM -0400, Chase Douglas wrote:
>> >> This change adds tracing_off_event() calls, which stop debug tracing,
>> >> when a BUG() or WARN() function is called. The stoppage depends on
>> >> commandline paramenter tracing_off={bug,warn,none}. The default is
>> >> "bug", so only the BUG() paths will stop tracing.
>> >>
>> >> Signed-off-by: Chase Douglas <chase.douglas@...onical.com>
>> >
>> >
>> > ACK
>> >
>> > But I can't find where we call oops_enter() from panic()
>> > I see it called in x86 from oops_begin() that is called
>> > in various places like die(), but couldn't find how it
>> > ends up beeing called from panic().
>>
>> I did not test the panic() path, but when that happens the system goes
>> down anyways. You won't be able to get the ftrace unless you enable
>> the ftrace on oops option, in which case the end of the trace will
>> likely be close enough to what you are looking for anyways.
>
>
> Yeah but there is also a sysrq that can trigger an ftrace dump.
> So if you forgot ftrace dump on oops and you want to use the sysrq
> then you don't want the tracing to continue between the panic and
> the time for your fingers to reach the keyboard (that notwithstanding
> the time to remember the right combination...which I always forget).

Ahhh, I can see where this would be useful then. I'll just add an
event to panic() like I did the other paths.

-- Chase
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