From: Peter Zijlstra <peterz@infradead.org>
To: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vivek Goyal <vgoyal@redhat.com>,
linux-doc@vger.kernel.org, x86@kernel.org,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
Michal Hocko <mhocko@kernel.org>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Subject: Re: [V3 PATCH 3/4] kexec: Fix race between panic() and crash_kexec() called directly
Date: Fri, 21 Aug 2015 01:08:45 +0200 [thread overview]
Message-ID: <20150820230845.GF3161@worktop.event.rightround.com> (raw)
In-Reply-To: <20150806054543.25766.5914.stgit@softrs>
On Thu, Aug 06, 2015 at 02:45:43PM +0900, Hidehiro Kawai wrote:
> void crash_kexec(struct pt_regs *regs)
> {
> + int old_cpu, this_cpu;
> +
> + /*
> + * `old_cpu == -1' means we are the first comer and crash_kexec()
> + * was called without entering panic().
> + * `old_cpu == this_cpu' means crash_kexec() was called from panic().
> + */
> + this_cpu = raw_smp_processor_id();
> + old_cpu = atomic_cmpxchg(&panic_cpu, -1, this_cpu);
> + if (old_cpu != -1 && old_cpu != this_cpu)
> + return;
This allows recursive calling of crash_kexec(), the Changelog did not
mention that. Is this really required?
> +
> /* Take the kexec_mutex here to prevent sys_kexec_load
> * running on one cpu from replacing the crash kernel
> * we are using after a panic on a different cpu.
next prev parent reply other threads:[~2015-08-20 23:08 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-06 5:45 [V3 PATCH 0/4] Fix race issues among panic, NMI and crash_kexec Hidehiro Kawai
2015-08-06 5:45 ` [V3 PATCH 4/4] x86/apic: Introduce noextnmi boot option Hidehiro Kawai
2015-08-06 5:45 ` [V3 PATCH 3/4] kexec: Fix race between panic() and crash_kexec() called directly Hidehiro Kawai
2015-08-20 23:08 ` Peter Zijlstra [this message]
2015-08-22 2:35 ` 河合英宏 / KAWAI，HIDEHIRO
2015-08-25 14:52 ` Peter Zijlstra
2015-08-26 3:11 ` 河合英宏 / KAWAI，HIDEHIRO
2015-08-31 8:53 ` 河合英宏 / KAWAI，HIDEHIRO
2015-08-31 9:07 ` Peter Zijlstra
2015-08-31 9:57 ` 河合英宏 / KAWAI，HIDEHIRO
2015-08-06 5:45 ` [V3 PATCH 2/4] panic/x86: Allow cpus to save registers even if they are looping in NMI context Hidehiro Kawai
2015-08-20 23:18 ` Peter Zijlstra
2015-08-22 1:43 ` 河合英宏 / KAWAI，HIDEHIRO
2015-08-06 5:45 ` [V3 PATCH 1/4] panic/x86: Fix re-entrance problem due to panic on NMI Hidehiro Kawai
2015-08-20 23:45 ` Peter Zijlstra
2015-08-22 0:46 ` 河合英宏 / KAWAI，HIDEHIRO
2015-08-07 14:38 ` [V3 PATCH 0/4] Fix race issues among panic, NMI and crash_kexec Michal Hocko
2015-08-20 23:17 ` Peter Zijlstra
2015-08-22 0:41 ` 河合英宏 / KAWAI，HIDEHIRO
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