linux-kernel - Re: [PATCH] panic: remove redundant panic-cpu backtrace

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Message-ID: <2kwymhiz4fcozfmbmj6ju2qatsbmnrtiidfa4nxrqutgwa6xfy@dbf3caohbbay>
Date: Thu, 31 Jul 2025 16:32:30 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Petr Mladek <pmladek@...e.com>, 
	Feng Tang <feng.tang@...ux.alibaba.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] panic: remove redundant panic-cpu backtrace

On (25/07/31 09:15), John Ogness wrote:
> On 2025-07-31, Sergey Senozhatsky <senozhatsky@...omium.org> wrote:
> > SYS_INFO_ALL_CPU_BT sends NMI backtrace request to
> > all CPUs, which dumps an extra backtrace on panic CPU.
> 
> Isn't this only true if CONFIG_DEBUG_BUGVERBOSE=y?

Are you referring to vpanic()->dump_stack()?

Another way to get backtrace on panic CPU is via BUG(), which routes
through die()->__die_body(), which prints registers, stack trace,
and so on, before it calls into panic().  This might be x86 specific,
though.

> Also, the information is not the same. trigger_all_cpu_backtrace() will
> also dump the registers. For CONFIG_DEBUG_BUGVERBOSE=y on the panic CPU,
> only the stack is dumped.

Hmm, it's getting complicated, probably isn't worth it then.