linux-kernel - Re: [PATCH] LoongArch: Check unwind_error() in arch_stack

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Date:   Tue, 21 Mar 2023 07:25:46 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Xi Ruoyao <xry111@...111.site>
Cc:     Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org, loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH] LoongArch: Check unwind_error() in arch_stack_walk()

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@...ck-us.net>
> > Link: https://lore.kernel.org/all/8a44ad71-68d2-4926-892f-72bfc7a67e2a@roeck-us.net/
> > Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> 
> The fix makes sense, but I'm asking the same question again (sorry if
> it's noisy): should we Cc stable@...r.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.

Thanks,
Guenter