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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69607C433EF for ; Mon, 8 Nov 2021 10:13:11 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 24768610F8 for ; Mon, 8 Nov 2021 10:13:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 24768610F8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=alien8.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.223175.385766 (Exim 4.92) (envelope-from ) id 1mk1ds-0001Dh-MD; Mon, 08 Nov 2021 10:12:44 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 223175.385766; Mon, 08 Nov 2021 10:12:44 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mk1ds-0001Da-IG; Mon, 08 Nov 2021 10:12:44 +0000 Received: by outflank-mailman (input) for mailman id 223175; Mon, 08 Nov 2021 10:12:43 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mk1dr-0000dK-0y for xen-devel@lists.xenproject.org; Mon, 08 Nov 2021 10:12:43 +0000 Received: from mail.skyhub.de (mail.skyhub.de [5.9.137.197]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 68c7ac1a-407c-11ec-9787-a32c541c8605; Mon, 08 Nov 2021 11:12:42 +0100 (CET) Received: from zn.tnic (p200300ec2f33110088892b77bd117736.dip0.t-ipconnect.de [IPv6:2003:ec:2f33:1100:8889:2b77:bd11:7736]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 97BC51EC0535; Mon, 8 Nov 2021 11:12:41 +0100 (CET) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 68c7ac1a-407c-11ec-9787-a32c541c8605 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1636366361; 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=ZSl40zXDlt+0/rSkoDA+/axSBICuEw4xrW9t+JeAzRg=; b=O9utTH7kzvF0ogbSAjrVux8Q2NyGvuXt2DXX+lXMfGwQDD5NsnAlA7vS1HO+tdNI+F2ntn CZwfQStJuxv3i5Q66Ie7iUHTOBEhoA6pq6felnVAUxHBDq6LlMPMTRyA2hQo7p+FfRiqlX omkNlvF2ej63UhZNrO1CmPB0HckLABU= From: Borislav Petkov To: LKML Cc: Thomas Gleixner , Arnd Bergmann , Ayush Sawal , Greg Kroah-Hartman , Rohit Maheshwari , Steven Rostedt , Vinay Kumar Yadav , alsa-devel@alsa-project.org, bcm-kernel-feedback-list@broadcom.com, intel-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, linux-crypto@vger.kernel.org, linux-edac@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-iio@vger.kernel.org, linux-leds@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-remoteproc@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-sh@vger.kernel.org, linux-staging@lists.linux.dev, linux-tegra@vger.kernel.org, linux-um@lists.infradead.org, linux-usb@vger.kernel.org, linux-xtensa@linux-xtensa.org, netdev@vger.kernel.org, openipmi-developer@lists.sourceforge.net, rcu@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, xen-devel@lists.xenproject.org Subject: [PATCH v0 42/42] notifier: Return an error when callback is already registered Date: Mon, 8 Nov 2021 11:11:57 +0100 Message-Id: <20211108101157.15189-43-bp@alien8.de> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20211108101157.15189-1-bp@alien8.de> References: <20211108101157.15189-1-bp@alien8.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Borislav Petkov The notifier registration routine doesn't return a proper error value when a callback has already been registered, leading people to track whether that registration has happened at the call site: https://lore.kernel.org/amd-gfx/20210512013058.6827-1-mukul.joshi@amd.com/ Which is unnecessary. Return -EEXIST to signal that case so that callers can act accordingly. Enforce callers to check the return value, leading to loud screaming during build: arch/x86/kernel/cpu/mce/core.c: In function ‘mce_register_decode_chain’: arch/x86/kernel/cpu/mce/core.c:167:2: error: ignoring return value of \ ‘blocking_notifier_chain_register’, declared with attribute warn_unused_result [-Werror=unused-result] blocking_notifier_chain_register(&x86_mce_decoder_chain, nb); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Drop the WARN too, while at it. Suggested-by: Thomas Gleixner Signed-off-by: Borislav Petkov Cc: Arnd Bergmann Cc: Ayush Sawal Cc: Greg Kroah-Hartman Cc: Rohit Maheshwari Cc: Steven Rostedt Cc: Vinay Kumar Yadav Cc: alsa-devel@alsa-project.org Cc: bcm-kernel-feedback-list@broadcom.com Cc: intel-gfx@lists.freedesktop.org Cc: intel-gvt-dev@lists.freedesktop.org Cc: linux-alpha@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-clk@vger.kernel.org Cc: linux-crypto@vger.kernel.org Cc: linux-edac@vger.kernel.org Cc: linux-fbdev@vger.kernel.org Cc: linux-hyperv@vger.kernel.org Cc: linux-iio@vger.kernel.org Cc: linux-leds@vger.kernel.org Cc: linux-mips@vger.kernel.org Cc: linux-parisc@vger.kernel.org Cc: linux-pm@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-remoteproc@vger.kernel.org Cc: linux-renesas-soc@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linux-scsi@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: linux-staging@lists.linux.dev Cc: linux-tegra@vger.kernel.org Cc: linux-um@lists.infradead.org Cc: linux-usb@vger.kernel.org Cc: linux-xtensa@linux-xtensa.org Cc: netdev@vger.kernel.org Cc: openipmi-developer@lists.sourceforge.net Cc: rcu@vger.kernel.org Cc: sparclinux@vger.kernel.org Cc: x86@kernel.org Cc: xen-devel@lists.xenproject.org --- include/linux/notifier.h | 8 ++++---- kernel/notifier.c | 36 +++++++++++++++++++----------------- 2 files changed, 23 insertions(+), 21 deletions(-) diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 87069b8459af..45cc5a8d0fd8 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -141,13 +141,13 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); #ifdef __KERNEL__ -extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, +extern int __must_check atomic_notifier_chain_register(struct atomic_notifier_head *nh, struct notifier_block *nb); -extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, +extern int __must_check blocking_notifier_chain_register(struct blocking_notifier_head *nh, struct notifier_block *nb); -extern int raw_notifier_chain_register(struct raw_notifier_head *nh, +extern int __must_check raw_notifier_chain_register(struct raw_notifier_head *nh, struct notifier_block *nb); -extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, +extern int __must_check srcu_notifier_chain_register(struct srcu_notifier_head *nh, struct notifier_block *nb); extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, diff --git a/kernel/notifier.c b/kernel/notifier.c index b8251dc0bc0f..451ef3f73ad2 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -20,13 +20,11 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list); */ static int notifier_chain_register(struct notifier_block **nl, - struct notifier_block *n) + struct notifier_block *n) { while ((*nl) != NULL) { - if (unlikely((*nl) == n)) { - WARN(1, "double register detected"); - return 0; - } + if (unlikely((*nl) == n)) + return -EEXIST; if (n->priority > (*nl)->priority) break; nl = &((*nl)->next); @@ -134,10 +132,11 @@ static int notifier_call_chain_robust(struct notifier_block **nl, * * Adds a notifier to an atomic notifier chain. * - * Currently always returns zero. + * Returns 0 on success, %-EEXIST on error. */ -int atomic_notifier_chain_register(struct atomic_notifier_head *nh, - struct notifier_block *n) +int __must_check +atomic_notifier_chain_register(struct atomic_notifier_head *nh, + struct notifier_block *n) { unsigned long flags; int ret; @@ -216,10 +215,11 @@ NOKPROBE_SYMBOL(atomic_notifier_call_chain); * Adds a notifier to a blocking notifier chain. * Must be called in process context. * - * Currently always returns zero. + * Returns 0 on success, %-EEXIST on error. */ -int blocking_notifier_chain_register(struct blocking_notifier_head *nh, - struct notifier_block *n) +int __must_check +blocking_notifier_chain_register(struct blocking_notifier_head *nh, + struct notifier_block *n) { int ret; @@ -335,10 +335,11 @@ EXPORT_SYMBOL_GPL(blocking_notifier_call_chain); * Adds a notifier to a raw notifier chain. * All locking must be provided by the caller. * - * Currently always returns zero. + * Returns 0 on success, %-EEXIST on error. */ -int raw_notifier_chain_register(struct raw_notifier_head *nh, - struct notifier_block *n) +int __must_check +raw_notifier_chain_register(struct raw_notifier_head *nh, + struct notifier_block *n) { return notifier_chain_register(&nh->head, n); } @@ -406,10 +407,11 @@ EXPORT_SYMBOL_GPL(raw_notifier_call_chain); * Adds a notifier to an SRCU notifier chain. * Must be called in process context. * - * Currently always returns zero. + * Returns 0 on success, %-EEXIST on error. */ -int srcu_notifier_chain_register(struct srcu_notifier_head *nh, - struct notifier_block *n) +int __must_check +srcu_notifier_chain_register(struct srcu_notifier_head *nh, + struct notifier_block *n) { int ret; -- 2.29.2