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Date: Thu, 06 Nov 2014 17:52:05 -0500
From: Prarit Bhargava <prarit@redhat.com>
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To: Vivek Goyal <vgoyal@redhat.com>
CC: David Rientjes <rientjes@google.com>, linux-kernel@vger.kernel.org,
        Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Rusty Russell <rusty@rustcorp.com.au>,
        "H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Fabian Frederick <fabf@skynet.be>, isimatu.yasuaki@jp.fujitsu.com,
        jbaron@akamai.com, linux-doc@vger.kernel.org,
        kexec@lists.infradead.org, linux-api@vger.kernel.org
Subject: Re: [PATCH v8] kernel, add panic_on_warn
References: <1415187736-16242-1-git-send-email-prarit@redhat.com> <alpine.DEB.2.10.1411051357050.31575@chino.kir.corp.google.com> <545B733C.6080903@redhat.com> <alpine.DEB.2.10.1411061352440.1526@chino.kir.corp.google.com> <20141106220731.GA13590@redhat.com>
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On 11/06/2014 05:07 PM, Vivek Goyal wrote:
> On Thu, Nov 06, 2014 at 01:57:36PM -0800, David Rientjes wrote:
> 
> [..]
>> You see that doing
>>
>> 	if (panic_on_warn) {
>> 		panic_on_warn = 0;
>> 		panic(...);
>> 	}
>>
>> is racy, I hope.  If two threads WARN() at the same time, then there's 
>> nothing preventing a double panic() because WARN() itself is not 
>> serialized against anything.  So both the current comment and your 
>> suggested revision comment are bogus.
> 
> panic() is serialized on panic_lock. So I guess it is fine to hit WARN()
> on multiple cpus. Do you see an issue there?

Oops -- didn't see this until just now.

Once again, Vivek beat me to the punch :) and much more succinctly than I will
ever be able to do. :)

P.

> 
> Thanks
> Vivek
>