Re: [PATCH] LoongArch: Check unwind_error() in arch_stack_walk()

From: Huacai Chen <chenhuacai@kernel.org>
To: Guenter Roeck <linux@roeck-us.net>, stable <stable@vger.kernel.org>
Cc: Xi Ruoyao <xry111@xry111.site>,
	Tiezhu Yang <yangtiezhu@loongson.cn>,
	WANG Xuerui <kernel@xen0n.name>,
	loongarch@lists.linux.dev, linux-kernel@vger.kernel.org,
	loongson-kernel@lists.loongnix.cn
Subject: Re: [PATCH] LoongArch: Check unwind_error() in arch_stack_walk()
Date: Wed, 22 Mar 2023 08:50:07 +0800	[thread overview]
Message-ID: <CAAhV-H5kFRt9z0U_TqSQeqX9WuUJ2cg0LOboUXHp-fLR0PoTJg@mail.gmail.com> (raw)
In-Reply-To: <f61ac027-0068-40f0-87bd-17f916141884@roeck-us.net>

On Tue, Mar 21, 2023 at 10:25 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Tue, Mar 21, 2023 at 08:35:34PM +0800, Xi Ruoyao wrote:
> > On Tue, 2023-03-21 at 14:29 +0800, Tiezhu Yang wrote:
> > > We can see the following messages with CONFIG_PROVE_LOCKING=y on
> > > LoongArch:
> > >
> > >   BUG: MAX_STACK_TRACE_ENTRIES too low!
> > >   turning off the locking correctness validator.
> > >
> > > This is because stack_trace_save() returns a big value after call
> > > arch_stack_walk(), here is the call trace:
> > >
> > >   save_trace()
> > >     stack_trace_save()
> > >       arch_stack_walk()
> > >         stack_trace_consume_entry()
> > >
> > > arch_stack_walk() should return immediately if unwind_next_frame()
> > > failed, no need to do the useless loops to increase the value of
> > > c->len in stack_trace_consume_entry(), then we can fix the above
> > > problem.
> > >
> > > Reported-by: Guenter Roeck <linux@roeck-us.net>
> > > Link: https://lore.kernel.org/all/8a44ad71-68d2-4926-892f-72bfc7a67e2a@roeck-us.net/
> > > Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> >
> > The fix makes sense, but I'm asking the same question again (sorry if
> > it's noisy): should we Cc stable@vger.kernel.org and/or make a PR for
> > 6.3?
> >
> > To me a bug fixes should be backported into all stable branches affected
> > by the bug, unless there is some serious difficulty.  As 6.3 release
> > will work on launched 3A5000 boards out-of-box, people may want to stop
> > staying on the leading edge and use a LTS/stable release series. We
> > can't just say (or behave like) "we don't backport, please use latest
> > mainline" IMO :).
>
> It is a bug fix, isn't it ? It should be backported to v6.1+. Otherwise,
> if your policy is to not backport bug fixes, I might as well stop testing
> loongarch on all but the most recent kernel branch. Let me know if this is
> what you want. If so, I think you should let all other regression testers
> know that they should only test loongarch on mainline and possibly on
> linux-next.
This is of course a bug fix, but should Tiezhu resend this patch? Or
just replying to this message with CC stable@vger.kernel.org is
enough?

Huacai
>
> Thanks,
> Guenter