From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: paulmck@linux.vnet.ibm.com,
"zhangwei(Jovi)" <jovi.zhangwei@huawei.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>, Oleg Nesterov <oleg@redhat.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"yrl.pp-manager.tt@hitachi.com" <yrl.pp-manager.tt@hitachi.com>
Subject: Re: Re: [PATCH] tracing/uprobes: Support ftrace_event_file base multibuffer
Date: Tue, 18 Jun 2013 10:31:36 +0900 [thread overview]
Message-ID: <51BFB878.10508@hitachi.com> (raw)
In-Reply-To: <1371472393.18733.5.camel@gandalf.local.home>
(2013/06/17 21:33), Steven Rostedt wrote:
> On Mon, 2013-06-17 at 11:54 +0900, Masami Hiramatsu wrote:
>
>>> It makes a lot of sense to me, at least assuming no issues with the
>>> interrupts being disabled, but the checks not spotting this. Here
>>> is the check:
>>>
>>> preempt_count() != 0 || irqs_disabled()
>>>
>>> (With additional elaboration for if lockdep is enabled.)
>>
>> OK, I see. So I'll convert all the rcu_dereference_raw() to
>> rcu_dereference_sched() except kprobe handler, because in the
>> kprobe handler above check always be true. :)
>
> I would convert them all to rcu_dereference_sched(), the above check is
> only when CONFIG_DEBUG_LOCK_ALLOC is set. It also annotates what is
> protecting this variable. Please do not avoid a check because "it's
> always true here". You also get people copying that code (like for
> uprobes) and that will skip the check too.
>
> The only reason ftrace function tracer uses the raw (and now
> raw_notrace) version is because it is extremely invasive, and these
> checks done at *every* function call can actually live lock the system.
> But other places in tracing use the appropriate rcu_dereference_*()
> functions. If they do not, then they need to be fixed too.
Oh, I see.
Anyway, it will be completely replaced by the Oleg's patch.
Or should I fix that before his work?
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2013-06-18 1:31 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-14 1:44 [PATCH] tracing/uprobes: Support ftrace_event_file base multibuffer zhangwei(Jovi)
2013-06-14 13:21 ` Masami Hiramatsu
2013-06-14 13:51 ` Oleg Nesterov
2013-06-14 14:09 ` Oleg Nesterov
2013-06-14 15:31 ` Steven Rostedt
2013-06-14 16:21 ` Paul E. McKenney
2013-06-14 16:33 ` Steven Rostedt
2013-06-14 17:25 ` Paul E. McKenney
2013-06-17 2:54 ` Masami Hiramatsu
2013-06-17 12:33 ` Steven Rostedt
2013-06-18 1:31 ` Masami Hiramatsu [this message]
2013-06-18 2:02 ` Steven Rostedt
2013-06-14 14:44 ` Oleg Nesterov
2013-06-14 16:04 ` ftrace multibuffer && rcu (Was: tracing/uprobes: Support ftrace_event_file base multibuffer) Oleg Nesterov
2013-06-14 16:18 ` Oleg Nesterov
2013-06-14 16:26 ` Steven Rostedt
2013-06-14 17:02 ` Oleg Nesterov
2013-06-20 16:43 ` [PATCH] tracing/uprobes: Support ftrace_event_file base multibuffer Oleg Nesterov
2013-06-21 8:17 ` zhangwei(Jovi)
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