linux-kernel - Re: [PATCH 2/2] x86: make __get_wchan() use arch_stack

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Message-ID: <4aba3e74-a205-5dd1-69bc-9186c04e733d@bytedance.com>
Date:   Sun, 9 Apr 2023 14:30:23 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     peterz@...radead.org, keescook@...omium.org,
        dave.hansen@...ux.intel.com, bp@...en8.de, mingo@...hat.com,
        tglx@...utronix.de, rostedt@...dmis.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86: make __get_wchan() use arch_stack_walk()



On 2023/4/9 06:12, Josh Poimboeuf wrote:
> On Sat, Apr 08, 2023 at 01:36:06PM +0800, Qi Zheng wrote:
>>
>>
>> On 2023/4/8 13:08, Josh Poimboeuf wrote:
>>> On Thu, Mar 30, 2023 at 04:15:52PM +0800, Qi Zheng wrote:
>>>> Make __get_wchan() use arch_stack_walk() directly to
>>>> avoid open-coding of unwind logic.
>>>>
>>>> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
>>>
>>> Can we just have a shared version of __get_wchan() for all
>>> CONFIG_ARCH_STACKWALK arches?
>>
>>  From a quick glance, I think it's ok, but we still need to define
>> the arch's own get_wchan_cb(). I will try to do it.
> 
> Hm, why would we need to do that?

Because I see checks for count++ < 16 exist in __get_wchan() for some
arches and some don't. So I'm not sure if this check can be discarded
after using arch_stack_walk(). And I see that this check is retained in
arm64, see [1] for details.

[1]. 
https://github.com/torvalds/linux/commit/4f62bb7cb165f3e7b0a91279fe9dd5c56daf3457

> 

-- 
Thanks,
Qi