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Subject: Re: [PATCH] tracing: reduce latency and remove percpu trace_seq
From: Steven Rostedt <rostedt@goodmis.org>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Theodore Tso <tedtso@gmail.com>, Theodore Tso <tytso@mit.edu>,
        linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Frederic Weisbecker <fweisbec@gmail.com>
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Date: Tue, 20 Jul 2010 22:03:01 -0400
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On Mon, 2010-06-07 at 15:50 +0800, Lai Jiangshan wrote:
> Steven Rostedt wrote:
> > On Fri, 2010-06-04 at 10:23 +0800, Lai Jiangshan wrote:
> >> Steven Rostedt wrote:
> >>
> >>> The "print" in the trace_seq_printf() is the TP_printk() field of the
> >>> TRACE_EVENT. I believe that there were some events (ext4?) that did
> >>> things that required preemption disabled.
> >>>
> >> It seems that ext4 has no such events.
> >> I find jbd2_dev_to_name() in the TP_printk() field of ext4's tracepoints.
> >> And it seems that jbd2_dev_to_name() requires preemption enabled and sleepable.
> >>
> >> Maybe there were some events did things that required preemption disabled.
> >> But No document ensure TP_printk() preemption disabled, such events should
> >> be fixed, I think.
> > 
> > Well, I had a private email conversation with Ted last year where IIRC,
> > adding the preempt disable would fix things.
> > 
> > I'd like to make sure Ted is OK with removing that before we do so.
> > 
> > Ted?
> > 
> 
> Hi, Ted
> 
> Could you give some comments?
> I'm waiting and will appreciate your help.

Since I've not heard anything, I'm pulling this in for 2.6.36.

-- Steve