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 X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29245C433E0 for ; Thu, 11 Feb 2021 06:15:56 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D32F364E77 for ; Thu, 11 Feb 2021 06:15:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D32F364E77 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4DbmbC4gPTzDwfr for ; Thu, 11 Feb 2021 17:15:51 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=csgroup.eu (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@csgroup.eu; receiver=) Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4DbmXs5cmjzDwkm for ; Thu, 11 Feb 2021 17:13:42 +1100 (AEDT) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4DbmXc2c03z9v00m; Thu, 11 Feb 2021 07:13:36 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id XVriXF1VhpHq; Thu, 11 Feb 2021 07:13:36 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4DbmXc1gTkz9v00l; Thu, 11 Feb 2021 07:13:36 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 1C3958B815; Thu, 11 Feb 2021 07:13:37 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id e9Aiw-FGIZwf; Thu, 11 Feb 2021 07:13:37 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id A3DA28B771; Thu, 11 Feb 2021 07:13:36 +0100 (CET) Subject: Re: Declaring unrecoverable_exception() as __noreturn ? To: Michael Ellerman , Nicholas Piggin , "linuxppc-dev@lists.ozlabs.org" References: <5ecc1a9a-92eb-7006-6c94-2b7b700d182a@csgroup.eu> <1613004125.9jpd8u2w0w.astroid@bobo.none> <87mtwbnrlf.fsf@mpe.ellerman.id.au> From: Christophe Leroy Message-ID: <251d7de1-bb72-a949-6e64-e342a3becdfd@csgroup.eu> Date: Thu, 11 Feb 2021 07:13:37 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <87mtwbnrlf.fsf@mpe.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 11/02/2021 à 05:41, Michael Ellerman a écrit : > Nicholas Piggin writes: >> Excerpts from Christophe Leroy's message of February 11, 2021 2:44 am: >>> As far as I can see, almost all callers of unrecoverable_exception() expect it to never return. >>> >>> Can we mark it __noreturn ? >> >> I don't see why not, do_exit is noreturn. We could make die() noreturn >> as well. > > I'm always nervous about that, because we can return if a debugger is > involved: > > DEFINE_INTERRUPT_HANDLER(unrecoverable_exception) Hum ... Is that correct to define it as an interrupt handler ? Also, I see it declared a second time in interrupt.c, this time not as an interrupt handler. Is that wanted ? > { > pr_emerg("Unrecoverable exception %lx at %lx (msr=%lx)\n", > regs->trap, regs->nip, regs->msr); > die("Unrecoverable exception", regs, SIGABRT); > } > > void die(const char *str, struct pt_regs *regs, long err) > { > unsigned long flags; > > /* > * system_reset_excption handles debugger, crash dump, panic, for 0x100 > */ > if (TRAP(regs) != 0x100) { > if (debugger(regs)) > return; > > > We obviously don't want to optimise for that case, but it worries me > slightly if we're marking things noreturn when they can actually return. > I don't think I want to declare die() as __noreturn, need to look at it more in details first. Christophe