linux-kernel - Re: x86: A process doesn't stop on hw breakpoints sometimes

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Message-ID: <CANaxB-y-mBCnLMkfecPXYEQEYREDRWCY3Q-QOhp832ZLsLXycQ@mail.gmail.com>
Date:	Mon, 23 May 2016 18:28:07 -0700
From:	Andrei Vagin <avagin@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: Re: x86: A process doesn't stop on hw breakpoints sometimes

On Mon, May 23, 2016 at 4:05 PM, Andrei Vagin <avagin@...il.com> wrote:
> Hi,
>
> We use breakpoints on CRIU to stop a processes before calling
> rt_sigreturn and we found that sometimes a process runs through a
> break-point without stopping on it.
>
> https://github.com/xemul/criu/issues/162
>
>
> A small reproducer is attached. It forks a child, stops it, sets a
> breakpoint, executes a child, waits when it stops on the breakpoint. I
> execute it a few times concurrently and wait a few minutes.
>
> https://asciinema.org/a/006l3u5v82ubbkfy9fto07agd

I reproduced this issue on 4.4.9-300.fc23.x86_64

>
> I know that it can be reproduced on:
> AMD A10 Micro-6700T
> Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
> Intel(R) Core(TM) i7-4600U CPU @ 2.10GHz
>
> so It doesn't look like a bug in a processor.
>
> Thanks,
> Andrew