Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1236211

Re: Re: [V4 PATCH 3/4] kexec: Fix race between panic() and crash_kexec() called directly

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: Re: [V4 PATCH 3/4] kexec: Fix race between panic() and crash_kexec() called directly
Date 2015-09-30 14:00 +0200
Message-ID <qeodc-468-9@gated-at.bofh.it> (permalink)
References <qczZ8-T1-9@gated-at.bofh.it> <qdxLz-2vE-9@gated-at.bofh.it> <qdAJs-6Z2-17@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On Mon, Sep 28, 2015 at 07:08:19AM +0000, 河合英宏 / KAWAI，HIDEHIRO wrote:
> > >> kernel/kexec_core.c:899:3: note: in expansion of macro 'atomic_xchg'
> >       atomic_xchg(&panic_cpu, -1);
> >       ^
> 
> I changed to use atomic_xchg() instead of atomic_set() in V3
> because atomic_set() doesn't mean memory barrier.  However,
> I thought again and there is no need of barrier; there is no
> problem if a competitor sees old value of panic_cpu or new one.
> So, atomic_set() is sufficient and using it will remove this warning.
> 
> I will resend the fixed version later.

So if you rely on the memory barrier; you should have also put a comment
on explaining the ordering requirements.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[V4 PATCH 0/4] Fix race issues among panic, NMI and crash_kexec Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> - 2015-09-25 14:10 +0200
  [V4 PATCH 3/4] kexec: Fix race between panic() and crash_kexec()  called directly Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> - 2015-09-25 14:10 +0200
    Re: [V4 PATCH 3/4] kexec: Fix race between panic() and crash_kexec()  called directly kbuild test robot <lkp@intel.com> - 2015-09-28 06:10 +0200
      RE: Re: [V4 PATCH 3/4] kexec: Fix race between panic() and  crash_kexec() called directly 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-09-28 06:50 +0200
    RE: Re: [V4 PATCH 3/4] kexec: Fix race between panic() and  crash_kexec() called directly 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-09-28 09:10 +0200
      Re: Re: [V4 PATCH 3/4] kexec: Fix race between panic() and  crash_kexec() called directly Peter Zijlstra <peterz@infradead.org> - 2015-09-30 14:00 +0200
        RE: Re: [V4 PATCH 3/4] kexec: Fix race between panic() and  crash_kexec() called directly 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-01 04:10 +0200
  [V4 PATCH 1/4] panic/x86: Fix re-entrance problem due to panic on  NMI Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> - 2015-09-25 14:10 +0200
    RE: [V4 PATCH 1/4] panic/x86: Fix re-entrance problem due to panic  on NMI 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-09-25 14:20 +0200
      Re: [V4 PATCH 1/4] panic/x86: Fix re-entrance problem due to panic  on NMI Peter Zijlstra <peterz@infradead.org> - 2015-09-30 13:30 +0200
        RE: [V4 PATCH 1/4] panic/x86: Fix re-entrance problem due to panic  on NMI 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-01 03:10 +0200
  [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> - 2015-09-25 14:10 +0200
    Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Peter Zijlstra <peterz@infradead.org> - 2015-09-30 14:00 +0200
      RE: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-01 04:40 +0200
        Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Peter Zijlstra <peterz@infradead.org> - 2015-10-01 08:30 +0200
          RE: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-01 09:10 +0200
            Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Borislav Petkov <bp@alien8.de> - 2015-10-01 10:50 +0200
              RE: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-01 12:30 +0200
                Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Borislav Petkov <bp@alien8.de> - 2015-10-01 13:10 +0200
                RE: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-02 03:00 +0200
                Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Borislav Petkov <bp@alien8.de> - 2015-10-02 09:50 +0200
                RE: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-05 04:10 +0200
                Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Borislav Petkov <bp@alien8.de> - 2015-10-05 10:30 +0200
                RE: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-05 11:30 +0200
                Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Borislav Petkov <bp@alien8.de> - 2015-10-05 12:20 +0200
  [V4 PATCH 2/4] panic/x86: Allow cpus to save registers even if they  are looping in NMI context Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> - 2015-09-25 14:10 +0200
    Re: [V4 PATCH 2/4] panic/x86: Allow cpus to save registers even if  they are looping in NMI context Peter Zijlstra <peterz@infradead.org> - 2015-09-30 14:00 +0200
      RE: [V4 PATCH 2/4] panic/x86: Allow cpus to save registers even if  they are looping in NMI context 河合英宏 / KAWAI，HIDEHIRO   <hidehiro.kawai.ez@hitachi.com> - 2015-10-01 03:50 +0200

csiph-web