linux-kernel - Re: [PATCH] watchdog/hardlockup: Avoid large stack frames in watchdog_hardlockup

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Message-ID: <ZMoFWK0uGdneJYVc@dhcp22.suse.cz>
Date:   Wed, 2 Aug 2023 09:27:20 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        kernel test robot <lkp@...el.com>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        Pingfan Liu <kernelfans@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog/hardlockup: Avoid large stack frames in
 watchdog_hardlockup_check()

On Tue 01-08-23 08:41:49, Doug Anderson wrote:
[...]
> Ah, I see what you mean. The one issue I have with your solution is
> that the ordering of the stack crawls is less ideal in the "dump all"
> case when cpu != this_cpu. We really want to see the stack crawl of
> the locked up CPU first and _then_ see the stack crawls of other CPUs.
> With your solution the locked up CPU will be interspersed with all the
> others and will be harder to find in the output (you've got to match
> it up with the "Watchdog detected hard LOCKUP on cpu N" message).
> While that's probably not a huge deal, it's nicer to make the output
> easy to understand for someone trying to parse it...

Is it worth to waste memory for this arguably nicer output? Identifying
the stack of the locked up CPU is trivial. 
-- 
Michal Hocko
SUSE Labs