linux-kernel - Re: [PATCH -tip v3 0/7] kprobes/x86: Preempt related enhancements

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Date:   Thu, 21 Sep 2017 15:00:35 -0700
From:   Alexei Starovoitov <ast@...com>
To:     Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, <mingo@...hat.com>
CC:     <x86@...nel.org>, Steven Rostedt <rostedt@...dmis.org>,
        <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH -tip v3 0/7] kprobes/x86: Preempt related enhancements

On 9/19/17 2:58 AM, Masami Hiramatsu wrote:
> Hi,
>
> Here is the 3rd version of the series to improve preempt
> related behavior in kprobes/x86. This actually includes
> many enhancements/fixes from the 2nd version, which is
>
> https://lkml.org/lkml/2017/9/11/482
>
> With the previous patch, lkp-bot reported that an issue
> ( https://lkml.org/lkml/2017/9/14/3 ) and I couldn't
> reproduce it. However, I found a suspicious bug and fixed
> it ([2/7]).
>
> Also, while I was checking the correct condition for
> *probe handlers in Documentation/kprobes.txt, I also
> found that current implementations for ftrace-based kprobe
> and optprobe were mis-reading the document.
>>>From the document, handlers must be run with preempt-
> disabled, but interrupt disabling is not guaranteed.
> So in the middle of this series, patches ([4/7],[5/7],
> [6/7]) adding preempt-disabling and removing irq-disabling.
>
> And at last, I placed the original patch (Enable optprobe
> with CONFIG_PREEMPT).
>
> The others are just for making sure this fix works well.
> - [1/7] is just adding preemptible checker in kprobe
>   smake tests so that we can easily find mistake.
> - [3/7] is adding an assert if user tries to change
>   execution path in optprobe, which is obviously
>   prohibited in the document (there also be how to
>   avoid it.)

all patches look great to me.
Acked-by: Alexei Starovoitov <ast@...nel.org>