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

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Message-ID: <CANaxB-xkUKgcYQR0n0dOPTKJOxqsxC=PHwB00hCchwB6VhY45A@mail.gmail.com>
Date:	Mon, 23 May 2016 22:30:02 -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 6:28 PM, Andrei Vagin <avagin@...il.com> wrote:
> 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

Oops. I can't reproduce this issue on 4.6 and 4.5. Looks like it was
fixed between 4.4 and 4.5. Sorry for the noise.

>
>>
>> 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