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Date:   Sun, 28 Aug 2022 21:49:23 -0700
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Subject: Re: [PATCH RFC 1/2] coding-style.rst: document BUG() and WARN() rules
 ("do not crash the kernel")
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To:     Linus Torvalds <torvalds@linux-foundation.org>,
        Dave Young <dyoung@redhat.com>
Cc:     David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-doc@vger.kernel.org,
        kexec@lists.infradead.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        David Laight <David.Laight@aculab.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Andy Whitcroft <apw@canonical.com>,
        Joe Perches <joe@perches.com>,
        Dwaipayan Ray <dwaipayanray1@gmail.com>,
        Lukas Bulwahn <lukas.bulwahn@gmail.com>,
        Baoquan He <bhe@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
        Stephen Johnston <sjohnsto@redhat.com>,
        Prarit Bhargava <prarit@redhat.com>
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From:   John Hubbard <jhubbard@nvidia.com>
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On 8/28/22 20:07, Linus Torvalds wrote:
> On Sun, Aug 28, 2022 at 6:56 PM Dave Young <dyoung@redhat.com> wrote:
>>
>>> John mentioned PANIC_ON().
>>
>> I would vote for PANIC_ON(), it sounds like a good idea, because
>> BUG_ON() is not obvious and, PANIC_ON() can alert the code author that
>> this will cause a kernel panic and one will be more careful before
>> using it.
> 
> People, NO.
> 
> We're trying to get rid of BUG_ON() because it kills the machine.
> 
> Not replace it with another bogus thing that kills a machine.

OK, this guidance, and the write-up that follows it, is all very clear,
except for one point...

> 
> So no PANIC_ON(). We used to have "panic()" many many years ago, we
> got rid of it. We're not re-introducing it.

...here. I count ~1000 calls to panic() in today's kernel, to a 
function in kernel/panic.c that shows no hint of being removed, nor
even deprecated. 

$ git grep -nw panic\( | wc -l
1321

Could you please clarify that point? (I'm not trying to debate 
policy, but rather, to figure out what we should write in the
documentation of the policy.)


thanks,

-- 
John Hubbard
NVIDIA