linux-kernel - Re: [PATCH] x86/smpboot: Mark native_play_dead() as _

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Message-Id: <EA25BB49-DCF0-4868-878D-8BC5217380A1@linux.dev>
Date: Mon, 27 Oct 2025 20:56:18 +0100
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>,
 Peter Zijlstra <peterz@...radead.org>,
 Sean Christopherson <seanjc@...gle.com>,
 Kai Huang <kai.huang@...el.com>,
 Brian Gerst <brgerst@...il.com>,
 Thomas Huth <thuth@...hat.com>,
 Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>,
 Zheyun Shen <szy0127@...u.edu.cn>,
 Kevin Loughlin <kevinloughlin@...gle.com>,
 K Prateek Nayak <kprateek.nayak@....com>,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
 Li Chen <chenl311@...natelecom.cn>,
 Tim Chen <tim.c.chen@...ux.intel.com>,
 Ingo Molnar <mingo@...nel.org>,
 Tom Lendacky <thomas.lendacky@....com>,
 Kevin Brodsky <kevin.brodsky@....com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/smpboot: Mark native_play_dead() as __noreturn

On 27. Oct 2025, at 20:28, Josh Poimboeuf wrote:
> On Mon, Oct 27, 2025 at 04:51:02PM +0100, Thorsten Blum wrote:
>> native_play_dead() ends by calling the non-returning function
>> hlt_play_dead() and therefore also never returns.
>> 
>> The !CONFIG_HOTPLUG_CPU stub version of native_play_dead()
>> unconditionally calls BUG() and does not return either.
>> 
>> Add the __noreturn attribute to both function definitions and their
>> declaration to document this behavior and to potentially improve
>> compiler optimizations.
>> 
>> Remove the obsolete comment, and add native_play_dead() to the objtool's
>> list of __noreturn functions.
>> 
>> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> 
> Is there an objtool warning that this fixes?  If so, it would be helpful
> to put it in the description above.

Not that I'm aware of.