From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
Tejun Heo <tj@kernel.org>,
linux-kernel@vger.kernel.org,
Sebastian Ott <sebott@linux.vnet.ibm.com>
Subject: Re: [PATCH] percpu: use notrace variant of preempt_disable/preempt_enable
Date: Tue, 8 Nov 2016 10:56:55 +0100 [thread overview]
Message-ID: <20161108105655.129ee2d7@mschwide> (raw)
In-Reply-To: <20161107122716.6e4597a7@gandalf.local.home>
On Mon, 7 Nov 2016 12:27:16 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Thu, 3 Nov 2016 14:58:38 +0100
> Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
>
> > Commit 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like
> > events do") added a couple of this_cpu_read calls to the ftrace code.
> >
> > On x86 this is not a problem, since it has single instructions to read
> > percpu data. Other architectures which use the generic variant now
> > have additional preempt_disable and preempt_enable calls in the core
> > ftrace code. This may lead to recursive calls and in result to a dead
> > machine, e.g. if preemption and debugging options are enabled.
> >
> > To fix this use the notrace variant of preempt_disable and
> > preempt_enable within the generic percpu code.
> >
> > Reported-and-bisected-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
> > Tested-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
> > Fixes: 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like events do")
> > Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
>
> Acked-by: Steven Rostedt <rostedt@goodmis.org>
>
> Feel free to push this in your tree.
Ok, will do. Thanks.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
prev parent reply other threads:[~2016-11-08 9:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-03 13:58 [PATCH] percpu: use notrace variant of preempt_disable/preempt_enable Heiko Carstens
2016-11-07 17:27 ` Steven Rostedt
2016-11-08 9:56 ` Martin Schwidefsky [this message]
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