From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C81EBC4332F for ; Wed, 23 Nov 2022 18:19:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238909AbiKWSTv (ORCPT ); Wed, 23 Nov 2022 13:19:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48904 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238816AbiKWSTq (ORCPT ); Wed, 23 Nov 2022 13:19:46 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB3C310FA for ; Wed, 23 Nov 2022 10:19:45 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 96D59B82215 for ; Wed, 23 Nov 2022 18:19:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3436CC433D6; Wed, 23 Nov 2022 18:19:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669227583; bh=HfKCxUf/kEaMg1EqZNQeaiJch/1K7iIS4r+c9bp1iXQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=aXnqfmRmmoF2y8Y1euD9uZ4PKDjWXASOgjU+dk3A/cuMWxMZ13O9gqwOS1nHGz9Ft SEgs2U7Gqgl03gHDZCje0dcXSSYjvn8rtDY/28mbUuth/2QzpOfbwnkY+swPBmF0tM Asi4/8pl/WmN9zQGpjeRLRJ/Hv09x7/Nrlg+W4REyiOXBug0OfaePFJJb/uS5f4107 C4uZB3oOW+VT2hFcAJG+E1byGg9KCm8lvOnBWLrCm55xClT7xRKmBSHWBvbAZh1f7J XQ50nDMhYUPZ9YcbmKCzhItf77Bt5OoYLCnnkgTeTJlSRU1enURNik03xJ1rerX2oo 6PxVzrZIn3WVg== Date: Wed, 23 Nov 2022 10:19:41 -0800 From: Josh Poimboeuf To: "Paul E. McKenney" Cc: Peter Zijlstra , sfr@canb.auug.org.au, linux-kernel@vger.kernel.org Subject: Re: objtool warning for next-20221118 Message-ID: <20221123181941.fh4hrr3pazelwtxc@treble> References: <20221121040736.GA3738360@paulmck-ThinkPad-P17-Gen-1> <20221121145215.GF4001@paulmck-ThinkPad-P17-Gen-1> <20221122051605.4hcbslwxez2trdvt@treble> <20221123002258.GR4001@paulmck-ThinkPad-P17-Gen-1> <20221123014812.7gptbvvndzemt5nc@treble> <20221123174951.GZ4001@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221123174951.GZ4001@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 23, 2022 at 09:49:51AM -0800, Paul E. McKenney wrote: > > > > Perhaps the best way would be to stick a REACHABLE annotation in > > > > arch_cpu_idle_dead() or something? > > > > > > When I apply this on -next, I still get the objtool complaint. > > > Is there something else I should also be doing? > > > > Silly GCC is folding the inline asm. This works (but still doesn't seem > > like the right approach): > > > > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c > > index 26e8f57c75ad..128e7d78fedf 100644 > > --- a/arch/x86/kernel/process.c > > +++ b/arch/x86/kernel/process.c > > @@ -702,7 +702,7 @@ static void (*x86_idle)(void); > > #ifndef CONFIG_SMP > > static inline void play_dead(void) > > { > > - BUG(); > > + _BUG_FLAGS(ASM_UD2, 0, ASM_REACHABLE); > > } > > #endif > > I tried this, and still get: > > vmlinux.o: warning: objtool: do_idle+0x156: unreachable instruction > > Maybe my gcc is haunted? Weird, it worked for me. I have gcc version 12.2.1 20220819 (Red Hat 12.2.1-2) (GCC) and I can't really fathom why that wouldn't work. Maybe it's a different issue? The "unreachable instruction" warning is limited to one, so when a first warning gets fixed, a second warning might suddenly become visible. Can you attach arch/x86/kernel/process.o? -- Josh