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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C5598C433EF for ; Wed, 15 Dec 2021 16:05:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=tNuUXwfv+zfoyG6UlOQiTeiBWl1ThIqowHFew8+heeQ=; b=1mx1jzU2kduO7R iYwDaE05Xn7ZIVyl1GKVb40F5c719C3hXAz/50vaVsCTM6Qvr27WqesKvSWp3wkAEhGTXEGvza+19 qHn7tAO0vvyeTqC/gMpTtMsctzqbbi2HT1Uq58X8rlaIj+2rLo5Bhyx2FgJUVV4TFYeo0bmJva5xZ PKsOr2arZ0Aa8zt6fvL4WvYZ1jzY/sWlfVTbxNoyz2+ydtKvXqx4fmou0fmwWNrbWS6bivXDNoiW6 vzNabLlmiZzJcKmWvu3uTPw0bspIpMF8rTMwSaclA0cfyBaT8jdvrOl+A+X9cSFlVBEbFLZfA5DhS nfnNhsoWzUog2p7XwkbQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mxWkb-001XG5-Vs; Wed, 15 Dec 2021 16:03:30 +0000 Received: from sin.source.kernel.org ([145.40.73.55]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mxWkC-001X4t-3R for linux-arm-kernel@lists.infradead.org; Wed, 15 Dec 2021 16:03:05 +0000 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 sin.source.kernel.org (Postfix) with ESMTPS id 6C5A5CE1AF2; Wed, 15 Dec 2021 16:03:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CABDC36AE1; Wed, 15 Dec 2021 16:02:58 +0000 (UTC) Date: Wed, 15 Dec 2021 16:02:55 +0000 From: Catalin Marinas To: Qian Cai Cc: Jianyong Wu , will@kernel.org, anshuman.khandual@arm.com, akpm@linux-foundation.org, ardb@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, david@redhat.com, gshan@redhat.com, justin.he@arm.com, nd@arm.com Subject: Re: [PATCH v2] arm64/mm: avoid fixmap race condition when create pud mapping Message-ID: References: <20211210095432.51798-1-jianyong.wu@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211215_080304_377791_FE696D81 X-CRM114-Status: GOOD ( 16.96 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Dec 15, 2021 at 09:13:37AM -0500, Qian Cai wrote: > On Fri, Dec 10, 2021 at 05:54:32PM +0800, Jianyong Wu wrote: > > fixmap is a global resource and is used recursively in create pud mapping. > > It may lead to race condition when alloc_init_pud is called concurrently. > > > > Fox example: > > alloc_init_pud is called when kernel_init. If memory hotplug > > thread, which will also call alloc_init_pud, happens during > > kernel_init, the race for fixmap occurs. > > > > The race condition flow can be: > > > > *************** begin ************** > > > > kerenl_init thread virtio-mem workqueue thread > > ================== ======== ================== > > alloc_init_pud(...) > > pudp = pud_set_fixmap_offset(..) alloc_init_pud(...) > > ... ... > > READ_ONCE(*pudp) //OK! pudp = pud_set_fixmap_offset( > > ... ... > > pud_clear_fixmap() //fixmap break > > READ_ONCE(*pudp) //CRASH! > > > > **************** end *************** > > > > Hence, a spin lock is introduced to protect the fixmap during create pdg > > mapping. > > > > Signed-off-by: Jianyong Wu > > I am afraid there is a problem to take a spinlock there. > > node 0 deferred pages initialised in 2740ms > pgdatinit0 (176) used greatest stack depth: 59184 bytes left > devtmpfs: initialized > KASLR disabled due to lack of seed > BUG: sleeping function called from invalid context at mm/page_alloc.c:5151 Thanks for the report. Definitely a bug, GFP_KERNEL_ACCOUNT allows for the page allocator to sleep. I'll drop the patch from the arm64 for-next/fixes branch for now and sort it out later. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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 0F4B7C433EF for ; Wed, 15 Dec 2021 16:03:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244058AbhLOQDD (ORCPT ); Wed, 15 Dec 2021 11:03:03 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:34874 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232640AbhLOQDB (ORCPT ); Wed, 15 Dec 2021 11:03:01 -0500 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 dfw.source.kernel.org (Postfix) with ESMTPS id 38D3761995 for ; Wed, 15 Dec 2021 16:03:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CABDC36AE1; Wed, 15 Dec 2021 16:02:58 +0000 (UTC) Date: Wed, 15 Dec 2021 16:02:55 +0000 From: Catalin Marinas To: Qian Cai Cc: Jianyong Wu , will@kernel.org, anshuman.khandual@arm.com, akpm@linux-foundation.org, ardb@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, david@redhat.com, gshan@redhat.com, justin.he@arm.com, nd@arm.com Subject: Re: [PATCH v2] arm64/mm: avoid fixmap race condition when create pud mapping Message-ID: References: <20211210095432.51798-1-jianyong.wu@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 15, 2021 at 09:13:37AM -0500, Qian Cai wrote: > On Fri, Dec 10, 2021 at 05:54:32PM +0800, Jianyong Wu wrote: > > fixmap is a global resource and is used recursively in create pud mapping. > > It may lead to race condition when alloc_init_pud is called concurrently. > > > > Fox example: > > alloc_init_pud is called when kernel_init. If memory hotplug > > thread, which will also call alloc_init_pud, happens during > > kernel_init, the race for fixmap occurs. > > > > The race condition flow can be: > > > > *************** begin ************** > > > > kerenl_init thread virtio-mem workqueue thread > > ================== ======== ================== > > alloc_init_pud(...) > > pudp = pud_set_fixmap_offset(..) alloc_init_pud(...) > > ... ... > > READ_ONCE(*pudp) //OK! pudp = pud_set_fixmap_offset( > > ... ... > > pud_clear_fixmap() //fixmap break > > READ_ONCE(*pudp) //CRASH! > > > > **************** end *************** > > > > Hence, a spin lock is introduced to protect the fixmap during create pdg > > mapping. > > > > Signed-off-by: Jianyong Wu > > I am afraid there is a problem to take a spinlock there. > > node 0 deferred pages initialised in 2740ms > pgdatinit0 (176) used greatest stack depth: 59184 bytes left > devtmpfs: initialized > KASLR disabled due to lack of seed > BUG: sleeping function called from invalid context at mm/page_alloc.c:5151 Thanks for the report. Definitely a bug, GFP_KERNEL_ACCOUNT allows for the page allocator to sleep. I'll drop the patch from the arm64 for-next/fixes branch for now and sort it out later. -- Catalin