linux-kernel - Re: [RFC PATCH] exit: Skip panic in do

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Message-ID: <20250414165043.GG28345@redhat.com>
Date: Mon, 14 Apr 2025 18:50:44 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Tze-nan Wu (吳澤南) <Tze-nan.Wu@...iatek.com>
Cc: Bobule Chang (張弘義) <bobule.chang@...iatek.com>,
	"brauner@...nel.org" <brauner@...nel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	wsd_upstream <wsd_upstream@...iatek.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"chenqiwu@...omi.com" <chenqiwu@...omi.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>
Subject: Re: [RFC PATCH] exit: Skip panic in do_exit() during poweroff

On 04/14, Tze-nan Wu (吳澤南) wrote:
>
> On Thu, 2025-04-10 at 23:05 +0200, Oleg Nesterov wrote:
> > 
> > As for sys_reboot(), I think that kernel_power_off() must be
> > __noreturn,
> > and sys_reboot() should use BUG() after
> > LINUX_REBOOT_CMD_POWER_OFF/_HALT
> > instead of do_exit().
> > 
> 
> Yes, kernel_power_off() should not return, but this is the case only if
> kernel_power_off() is invoked by PID 1 through sys_reboot().
> If kernel_power_off() is invoked by a kernel thread (e.g., the thermal
> kernel module) other than PID 1, then do_exit() could possibly be
> invoked by PID 1 after kernel_power_off() on another CPU.

Yes sure, this is clear.

I have mentioned sys_reboot() because (unless I am totally confused)
this connects to the previous report from Breno.

And I agree that we should do stop_other_cpus() first, but let me
say this again: I can't help ;)

But in any case, rightly or not I still think that the init process
should not exit/crash due to POWER_OFF/HALT. We should not mask this
problem in do_exit().

Oleg.