x86: A process doesn't stop on hw breakpoints sometimes

From	Andrei Vagin <avagin@gmail.com>
Newsgroups	linux.kernel
Subject	x86: A process doesn't stop on hw breakpoints sometimes
Date	2016-05-24 01:10 +0200
Message-ID	<rC790-3IA-9@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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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 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

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x86: A process doesn't stop on hw breakpoints sometimes Andrei Vagin <avagin@gmail.com> - 2016-05-24 01:10 +0200
  Re: x86: A process doesn't stop on hw breakpoints sometimes Andrei Vagin <avagin@gmail.com> - 2016-05-24 03:30 +0200
    Re: x86: A process doesn't stop on hw breakpoints sometimes Andrei Vagin <avagin@gmail.com> - 2016-05-24 07:40 +0200
  Re: x86: A process doesn't stop on hw breakpoints sometimes Andy Lutomirski <luto@amacapital.net> - 2016-05-24 03:40 +0200
    Re: x86: A process doesn't stop on hw breakpoints sometimes Oleg Nesterov <oleg@redhat.com> - 2016-05-25 01:40 +0200

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