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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CFEBCD6D251 for ; Thu, 28 Nov 2024 01:25:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4F85D6B0083; Wed, 27 Nov 2024 20:25:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4A87A6B0088; Wed, 27 Nov 2024 20:25:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3C7976B0083; Wed, 27 Nov 2024 20:25:27 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 1F1906B0083 for ; Wed, 27 Nov 2024 20:25:27 -0500 (EST) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id BBDFA40E70 for ; Thu, 28 Nov 2024 01:25:26 +0000 (UTC) X-FDA: 82833760800.25.AF0990C Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf13.hostedemail.com (Postfix) with ESMTP id EF6FC20008 for ; Thu, 28 Nov 2024 01:25:15 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=FKmA1PEC; dmarc=none; spf=pass (imf13.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1732757122; a=rsa-sha256; cv=none; b=Cjqi4JjkqHcZsVFly1ClB+csLYsUeNKs5joU+aSKz2K8W6qW477JctvnVGm7s6gJ+/ngYI mtan7BMw0jhom0fbk9mCMs/AwWFb600oBeNFOSynsTgXu0XXgO/KzC12rWr35nREYRgflc DG6EG6RUFoYEKGgjBkWN5ZOiLok4L70= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=FKmA1PEC; dmarc=none; spf=pass (imf13.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1732757122; h=from:from:sender: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:dkim-signature; bh=VMHYJD0RyO67S2qfb3e3KBi+TTrciPRuK/Snd5+iLfs=; b=Pq/vTOZoh+pluvuHGGu1H89QS1cXf1Bp4wjSmoBIrKa/hW+YdQEne4UX6WUlIKJ+RYfxfw +WZao7FI6Kflzt0dygHMCgKkjRZxYRtfyFnTcJRMuGDu+55fNkLoLHk3qAmLBIhPh/IfLm JmM4VYsM2Lm23JShqffGNUZf9eX70FI= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id D6C3D5C568C; Thu, 28 Nov 2024 01:24:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8BCBAC4CECC; Thu, 28 Nov 2024 01:25:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1732757123; bh=Anhspd9SqZzR8iiUfhU6EYjKkHaNq9O5YRWJhZnC28g=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=FKmA1PECOI242VDYy4zgJCsCOffx2r+jLL5i517LV73xQVvmDiPS21Txl/9tkV2Dx 2gjO5WUFgMoZefdK7uqI/QJV0jVL0k1xGz2tgUre3xE9a7WwFm7XcyoVhxdQcoe3rA rPColSQsqb7MkRWFNcz94Ww4JFDS5042LWNoeCtU= Date: Wed, 27 Nov 2024 17:25:23 -0800 From: Andrew Morton To: Marco Elver Cc: Andrey Konovalov , Alexander Potapenko , Dmitry Vyukov , Vlastimil Babka , Oscar Salvador , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, Sebastian Andrzej Siewior Subject: Re: [PATCH] stackdepot: fix stack_depot_save_flags() in NMI context Message-Id: <20241127172523.b12b82d150aad5069e024645@linux-foundation.org> In-Reply-To: <20241122154051.3914732-1-elver@google.com> References: <20241122154051.3914732-1-elver@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: EF6FC20008 X-Stat-Signature: 7jxwrqfg1exn1b7a9wfttntqmiif1yf5 X-HE-Tag: 1732757115-231858 X-HE-Meta: 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 Qe0LIeSP nL19JzRH7nfEaJX0jutZjQkv9aAvY3Mj/QwQJaNqACMLKQDIx5JuHHxMsCXEmFr8452jUAL/Z5mg2AqrsJVjQ3PdeQJAKeTQ7JWrq1EHa/MhYUxPup+VimyAaXyehZ4h3kHqzMEonolgj/t2kDaKCHe9BGyxD/Zxb7fi8Cum5rS7pDAtGctHp6APdEzS16I7bXSzpfxAbuxhjP3lpL5zq1mosv9CoTjW3T8V96tNMa+cMd4nNQ7QWRty/Sm6CH3/cPeKTnXt0oMcNzR9u+cKTKCRgb5ruMTwUYEi35Z+YaU+IEM0ocqlCPSxF/yZvpeUKXOkDGisNtQHaGpjXiXfuaqBOyHxHX+FqSHdj3GpopF9EVHbAQCDAEyYdDQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 22 Nov 2024 16:39:47 +0100 Marco Elver wrote: > Per documentation, stack_depot_save_flags() was meant to be usable from > NMI context if STACK_DEPOT_FLAG_CAN_ALLOC is unset. However, it still > would try to take the pool_lock in an attempt to save a stack trace in > the current pool (if space is available). > > This could result in deadlock if an NMI is handled while pool_lock is > already held. To avoid deadlock, only try to take the lock in NMI > context and give up if unsuccessful. Is it possible to trigger this deadlock in current kernels, or is this a might-happen-in-the-future thing? > The documentation is fixed to clearly convey this. >