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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 63112C433DF for ; Tue, 23 Jun 2020 21:33:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43FCD20707 for ; Tue, 23 Jun 2020 21:33:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393511AbgFWVdV (ORCPT ); Tue, 23 Jun 2020 17:33:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391365AbgFWVdO (ORCPT ); Tue, 23 Jun 2020 17:33:14 -0400 Received: from shards.monkeyblade.net (shards.monkeyblade.net [IPv6:2620:137:e000::1:9]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 827C9C061573; Tue, 23 Jun 2020 14:33:14 -0700 (PDT) Received: from localhost (unknown [IPv6:2601:601:9f00:477::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id C76DA129425B6; Tue, 23 Jun 2020 14:33:13 -0700 (PDT) Date: Tue, 23 Jun 2020 14:33:11 -0700 (PDT) Message-Id: <20200623.143311.995885759487352025.davem@davemloft.net> To: likaige@loongson.cn Cc: benve@cisco.com, _govind@gmx.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, lixuefeng@loongson.cn, yangtiezhu@loongson.cn Subject: Re: [PATCH RESEND] net/cisco: Fix a sleep-in-atomic-context bug in enic_init_affinity_hint() From: David Miller In-Reply-To: <1592899989-22049-1-git-send-email-likaige@loongson.cn> References: <1592899989-22049-1-git-send-email-likaige@loongson.cn> X-Mailer: Mew version 6.8 on Emacs 26.3 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Tue, 23 Jun 2020 14:33:14 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kaige Li Date: Tue, 23 Jun 2020 16:13:09 +0800 > The kernel module may sleep with holding a spinlock. > > The function call paths (from bottom to top) are: > > [FUNC] zalloc_cpumask_var(GFP_KERNEL) > drivers/net/ethernet/cisco/enic/enic_main.c, 125: zalloc_cpumask_var in enic_init_affinity_hint > drivers/net/ethernet/cisco/enic/enic_main.c, 1918: enic_init_affinity_hint in enic_open > drivers/net/ethernet/cisco/enic/enic_main.c, 2348: enic_open in enic_reset > drivers/net/ethernet/cisco/enic/enic_main.c, 2341: spin_lock in enic_reset > > To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC. > > Signed-off-by: Kaige Li Just grepping around for GFP_KERNEL usage in atomic contexts I guess is fine. But you really have to look at the bigger picture. Calling a NIC driver open function from a context holding a spinlock is very much the real problem, so many operations have to sleep and in face that ->ndo_open() method is defined as being allowed to sleep and that's why the core networking never invokes it with spinlocks held.