From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
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>,
Andrew Morton <akpm@linux-foundation.org>,
yrl.pp-manager.tt@hitachi.com
Subject: Re: [RFC PATCH -tip ] [BUGFIX] x86: Remove preempt disabling from kprobes
Date: Sat, 2 Jul 2011 11:39:29 +0530 [thread overview]
Message-ID: <20110702060929.GA5511@in.ibm.com> (raw)
In-Reply-To: <20110701131408.30886.45766.stgit@localhost.localdomain>
On Fri, Jul 01, 2011 at 10:14:08PM +0900, Masami Hiramatsu wrote:
> Steven Rostedt reported that putting kprobe on the instruction which
> loads preempt_count causes the wrong result, as below.
>
> Kprobes requires preemption to be disabled as it single steps the code
> it replaced with a breakpoint. But because the code that is single
> stepped could be reading the preempt count, the kprobe disabling of the
> preempt count can cause the wrong value to end up as a result. Here's an
> example:
...
> We just caused preempt count to increment twice when it should have only
> incremented once, and this screws everything else up.
>
> To solve this, I've removed preempt disabling code from kprobes,
> since the breakpoint exception and kprobes single step routine
> disables interrupts, it doesn't need to disable preemption while
> single-stepping anymore.
>
> This patch is for -tip tree, and it can be applied to linus tree too.
>
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Reported-by: Steven Rostedt <rostedt@goodmis.org>
> ---
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
next prev parent reply other threads:[~2011-07-02 6:09 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-30 13:23 [BUG] kprobes crashing because of preempt count 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 [this message]
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
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