From: Sasha Levin <sasha.levin@oracle.com>
To: Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>
Cc: Sasha Levin <sasha.levin@oracle.com>,
Dave Jones <davej@redhat.com>, Tejun Heo <tj@kernel.org>,
tglx@linutronix.de, LKML <linux-kernel@vger.kernel.org>,
trinity@vger.kernel.org
Subject: Re: timer: lockup in run_timer_softirq()
Date: Thu, 03 Apr 2014 16:43:33 -0400 [thread overview]
Message-ID: <533DC7F5.9090202@oracle.com> (raw)
In-Reply-To: <20130711171157.GL25631@dyad.programming.kicks-ass.net>
On 07/11/2013 01:11 PM, Peter Zijlstra wrote:
> On Thu, Jul 11, 2013 at 12:59:32PM -0400, Steven Rostedt wrote:
>> On Thu, 2013-07-11 at 12:55 -0400, Steven Rostedt wrote:
>>
>>>>
>>>> Other than that, a function tracer environment that is safer to use might be
>>>> useful for other people as well.
>>>
>>> Not sure how to make the environment safe, as the main purpose of the
>>> function trace is to debug those hard to debug locations, like NMIs,
>>> RCU, dynamic ticks, etc. To ensure a "safe" environment, it would
>>> cripple the tracer.
>>>
>>> Hmm, what would you state as a safe environment? How can we detect if
>>> the environment is safe to trace or not?
>>
>> Maybe I misunderstood you. You mean to have this environment be
>> something for not just perf, and have the macro be:
>>
>> NONSAFE_TRACE(__local_bh_enable);
>>
>> ?
>>
>> Then, any ftrace user could set a flag in the registering of its ops to
>> 'safe_only_functions'. And it will ignore all of these locations.
>> There's really not many of them, so it may not be too hard to weed out.
>
> Yah, like that. But that doesn't invalidate your question as to what 'safe'
> would encompass. I think RCU/lockdep would be the big thing for perf, not
> sure it should be wider than that.
Ping? There was no conclusion here and this issue is still ongoing in -next.
Thanks,
Sasha
next prev parent reply other threads:[~2014-04-03 20:43 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-09 22:35 timer: lockup in run_timer_softirq() Sasha Levin
2013-07-09 22:47 ` Dave Jones
2013-07-09 22:49 ` Sasha Levin
2013-07-09 23:03 ` Dave Jones
2013-07-09 23:09 ` Sasha Levin
2013-07-10 9:52 ` Peter Zijlstra
2013-07-10 12:27 ` Steven Rostedt
2013-07-10 12:42 ` Peter Zijlstra
2013-07-10 12:58 ` Steven Rostedt
2013-07-11 16:42 ` Peter Zijlstra
2013-07-11 16:55 ` Steven Rostedt
2013-07-11 16:59 ` Steven Rostedt
2013-07-11 17:11 ` Peter Zijlstra
2014-04-03 20:43 ` Sasha Levin [this message]
2013-07-10 9:54 ` Peter Zijlstra
2013-07-10 14:47 ` Sasha Levin
2013-07-11 10:02 ` Peter Zijlstra
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