From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 045D72F744A for ; Mon, 27 Oct 2025 16:23:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761582195; cv=none; b=OYshKPeviqTSPuzcsUxv1Ja1qpJHmqfMRlewcDLu/fuEgcxlX1+Q1ZdBE72yYPcGyJnbTA3S/HH4PST94/WjCZxDktU8+CeKjRkivJuvEaLJyiw+mXRWOxNg6AqOpSPkb9ac8/Omx+KMs7wgKG31xmSZOVB3Bq6+wleujeZSLdo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761582195; c=relaxed/simple; bh=Jelz6I4WuPxrY/RAWSkqZ9oeGLuIlocAzAleSI9eqKk=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=GhuIfPkeh11UXHEsac4Yt+83KIgvdSKv+GMn8ZsoIrt6qFaWCOjz4kNcsws7p1MZ9TJSF1sVzCkOG/3nZp+r9iJYe+lBxWHAiMXus63ctYhvI+SY+8OXzmIvyc40MCcz5U2zjmZB2kWKy4tKI1njnow2jwDRhsSfWQ3aFErb39E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=kB8jEMs4; arc=none smtp.client-ip=95.215.58.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="kB8jEMs4" Content-Type: text/plain; charset=us-ascii DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761582191; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WoyyB79oRMCcpGut9Qsij+6WxAVhCrAZdlg/NT9G6oY=; b=kB8jEMs47CnmCJnxfeHdeQBzEyeTI4zRgkelmRGItw+UaYUH5UpEXamft8s+e5mO3MyS7U vF8OMR2fcDJaPHwQ9W+RjLny21e4SVZTwWIvfl/Y1c3SS6JpYlHtsR/gVGqjRu0UbcKYil 3qCkkH9CJ705pimCYM+eFQSk77GPUxw= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3826.700.81\)) Subject: Re: x86/smpboot: Question regarding native_play_dead() __noreturn warning X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Thorsten Blum In-Reply-To: <4be37a6a-0a04-48f8-9399-25ecb4638cdc@redhat.com> Date: Mon, 27 Oct 2025 17:23:02 +0100 Cc: Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , linux-kernel@vger.kernel.org, x86@kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <58486755-0AA7-47DC-B914-1DF92483F69E@linux.dev> References: <47A8B84B-2685-4DA2-B39B-E55812374426@linux.dev> <20251027125045.GX4067720@noisy.programming.kicks-ass.net> <4be37a6a-0a04-48f8-9399-25ecb4638cdc@redhat.com> To: Waiman Long X-Migadu-Flow: FLOW_OUT On 27. Oct 2025, at 16:48, Waiman Long wrote: > On 10/27/25 8:50 AM, Peter Zijlstra wrote: >> On Mon, Oct 27, 2025 at 01:23:02PM +0100, Thorsten Blum wrote: >>> [...] >> I'm not sure either, it wasn't there in v2 but appeared in v3. >>=20 >> v2: 20230620140625.1001886-3-longman@redhat.com >> v3: 20230622003603.1188364-2-longman@redhat.com >>=20 >> The difference is that v2 tried to restore the msr after 'play_dead' >> which is silly, since it would never reach that code. v3 removed that >> dead restore code and added the confusing comment. >>=20 >> There is a clue here though: >>=20 >> 20230622054053.uy577qezu5a65buc@treble >>=20 >> Josh suggests play_dead() should be marked noreturn (which it is in >> current kernels). >>=20 >> Waiman then replies: >>=20 >> 921e1b98-af36-1f51-5abe-dea36425b706@redhat.com >>=20 >> which is utterly confused again. >=20 > I don't remember exactly how I got the warning when __noreturn is = added to native_play_dead(). It may be a limitation of the objtool or = gcc that I was using at that time. If Thorsten doesn't have problem = adding __noreturn, I won't mind him doing that and taking out the the = comment. We can see if there is other issue coming up in the future. Thanks for the quick replies! I submitted the patch adding __noreturn here: = https://lore.kernel.org/lkml/20251027155107.183136-1-thorsten.blum@linux.d= ev/