linux-kernel - Re: WARNING in tracing_func

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Date:   Fri, 24 Jan 2020 10:28:30 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        syzbot <syzbot+0c147ca7bd4352547635@...kaller.appspotmail.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: WARNING in tracing_func_proto

On Fri, 24 Jan 2020 11:44:13 +0100
Dmitry Vyukov <dvyukov@...gle.com> wrote:

> FWIW this is invalid use of WARN macros:
> https://elixir.bootlin.com/linux/v5.5-rc7/source/include/asm-generic/bug.h#L72
> This should be replaced with pr_err (if really necessary, kernel does
> not generally spew stacks on every ENOMEM/EINVAL).

That message was added in 2018. The WARN macro in question here, was
added in 2011. Thus, this would be more of a clean up fix.

> 
> There are no _lots_ such wrong uses of WARN in the kernel. There were
> some, all get fixed over time, we are still discovering long tail, but
> it's like one per months at most. Note: syzbot reports each and every
> WARNING. If there were lots, you would notice :)

Hmm, I haven't looked, but are all these correct usage?

 $ git grep WARN_ON HEAD | wc -l
15384

I also checked the number of WARN_ON when that WARN_ON was added:

 $ git grep WARN_ON 07d777fe8c3985bc83428c2866713c2d1b3d4129 | wc -l
4730

A lot more were added since then!

> 
> Sorting this out is critical for just any kernel testing. Otherwise no
> testing system will be able to say if a test triggers something bad in
> kernel or not.
> 
> FWIW there are no local trees for syzbot. It only tests public trees
> as is. Doing otherwise would not work/scale as a process.

Anyway, I'll happily take a patch converting that WARN_ON macro to a
pr_err() print.

-- Steve