From: Steven Rostedt <rostedt@goodmis.org>
To: ananth@in.ibm.com
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Frederic Weisbecker <fweisbec@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
yrl.pp-manager.tt@hitachi.com
Subject: Re: [BUG] kprobes crashing because of preempt count
Date: Fri, 01 Jul 2011 09:19:55 -0400 [thread overview]
Message-ID: <1309526395.26417.146.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <20110701130313.GA10935@in.ibm.com>
On Fri, 2011-07-01 at 18:33 +0530, Ananth N Mavinakayanahalli wrote:
> On Fri, Jul 01, 2011 at 09:01:00PM +0900, Masami Hiramatsu wrote:
> >
> > Yeah, it seems that same thing is done on arm too. And I'm sure that
> > However, I'm still not sure that entire int3 exec path can run without
> > calling inc_preempt_count.
> > It seems that the function is very primitive, and I doubt we can
> > allow to put kprobes on that...
>
> Right. I think all preempt manipulation routines need to be __kprobes.
>
As I stated earlier, it can be triggered on just a read of preempt
count. I would also hate to force preempt_count() reads and updates to
be function calls (that's the only way to make it __kprobes). The
inc/dec preempt count routines are only function calls if debug preempt
or preempt tracing is enabled, which is not the case on most distros.
Not to mention, I think reading the value of preempt count by kprobes is
a legit use case.
> Also, Steve is testing the -rt tree where artefacts related to
> locking/preemption are possibly quite different from the mainline that
> may also be at play here.
Yes, I noticed this first on an -rt variant. But I'm actually testing
patches to move from -rt to mainline. This happens to be more a mainline
issue. Once I noticed this bug, all my tests afterward was based on
v3.0-rc5.
-- Steve
prev parent reply other threads:[~2011-07-01 13:20 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-30 13:23 Steven Rostedt
2011-06-30 15:51 ` [RFC][PATCH] kprobes: Add separate preempt_disabling for kprobes Steven Rostedt
2011-06-30 16:14 ` Frederic Weisbecker
2011-06-30 16:46 ` Steven Rostedt
2011-06-30 19:40 ` Jason Baron
2011-06-30 19:42 ` Steven Rostedt
2011-06-30 21:56 ` Peter Zijlstra
2011-07-01 1:22 ` Masami Hiramatsu
2011-07-01 1:38 ` Steven Rostedt
2011-07-01 1:52 ` Masami Hiramatsu
2011-07-01 5:09 ` Masami Hiramatsu
2011-07-01 11:13 ` Masami Hiramatsu
2011-07-01 12:54 ` Steven Rostedt
2011-07-01 12:19 ` Steven Rostedt
2011-07-01 13:15 ` Masami Hiramatsu
2011-07-01 13:14 ` [RFC PATCH -tip ] [BUGFIX] x86: Remove preempt disabling from kprobes Masami Hiramatsu
2011-07-01 13:43 ` Steven Rostedt
2011-07-01 13:53 ` Steven Rostedt
2011-07-03 2:05 ` Masami Hiramatsu
2011-07-02 6:09 ` Ananth N Mavinakayanahalli
2011-07-01 1:12 ` [BUG] kprobes crashing because of preempt count Masami Hiramatsu
2011-07-01 1:33 ` Steven Rostedt
2011-07-01 2:23 ` Masami Hiramatsu
2011-07-01 11:36 ` Ananth N Mavinakayanahalli
2011-07-01 12:01 ` Masami Hiramatsu
2011-07-01 13:03 ` Ananth N Mavinakayanahalli
2011-07-01 13:19 ` Steven Rostedt [this message]
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