linux-kernel - Re: [PATCH] tracing: reduce latency and remove percpu trace

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Message-ID: <4C0CA4BE.9000703@cn.fujitsu.com>
Date:	Mon, 07 Jun 2010 15:50:22 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Theodore Tso <tedtso@...il.com>, Theodore Tso <tytso@....edu>
CC:	rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] tracing: reduce latency and remove percpu trace_seq

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.

Thanx, Lai
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