Re: [PATCH RFC 1/2] coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel")

John Hubbard
2022-08-29T04:49:36Z

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