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 850E6C3DA7A for ; Fri, 6 Jan 2023 17:38:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235632AbjAFRil (ORCPT ); Fri, 6 Jan 2023 12:38:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229949AbjAFRiW (ORCPT ); Fri, 6 Jan 2023 12:38:22 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6CA607D9DB for ; Fri, 6 Jan 2023 09:38:21 -0800 (PST) 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 D8AF661ED7 for ; Fri, 6 Jan 2023 17:38:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96A55C433EF; Fri, 6 Jan 2023 17:38:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673026700; bh=mVSb5WJNxb9CkrZLtlHqaTe+bEMhYwT0ZS0NE5kngJo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oPb9v8shkRWv2aUHwslq3X46cvS6dY8A7pPkMe1YRMrZjY+zzg1ecLol0MIE9yNAf J3EHogP5Z1HsWN5sNhF4uy7H4vGSQgMVfs8OrFhpp8GbzxgAbmqSEZ8WxqPEY4jxIE wyL5CXat6/M1HL9GflD3J6JcyU98X1n4XgVxM58N67CEg2L8KoyQlLZCmolEZWgAYL 3tFbUJ2eush/oWAfFtvDpb5Pho1roN5bhmFIeWxMMnSoVvL1V31ryaGWJZux6N//H1 6tbSJzqaJzyNdVEvmA+cYBeaqJLZ/78wDWiTAioAjy2soPiaL4R7U9TpD0nhmaeTbj n7mLWABL6ft8g== Date: Fri, 6 Jan 2023 17:38:15 +0000 From: Will Deacon To: Anders Roxell Cc: catalin.marinas@arm.com, mark.rutland@arm.com, james.morse@arm.com, ebiederm@xmission.com, elver@google.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, arnd@arndb.de Subject: Re: BUG: KCSAN: data-race in do_page_fault / spectre_v4_enable_task_mitigation Message-ID: <20230106173814.GA5169@willie-the-truck> References: <20221221145436.GF69385@mutt> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221221145436.GF69385@mutt> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 21, 2022 at 03:54:36PM +0100, Anders Roxell wrote: > Hey, > > I'm building an allmodconfig kernel on yesterdays linux-next (tag: > next-20221220) and I see a > "BUG: KCSAN: data-race in do_page_fault / spectre_v4_enable_task_mitigation" > when I boot up in QEMU. I ran the output via > scripts/decode_stacktrace.sh and this is what I see: > > > [ 2105.261121][ T154] ================================================================== > [ 2105.266067][ T154] BUG: KCSAN: data-race in do_page_fault / spectre_v4_enable_task_mitigation > [ 2105.271577][ T154] > [ 2105.273121][ T154] write to 0xffff8000210b3fb8 of 8 bytes by task 136 on cpu 0: > [ 2105.277743][ T154] spectre_v4_enable_task_mitigation (/home/anders/src/kernel/next/arch/arm64/kernel/proton-pack.c:651 /home/anders/src/kernel/next/arch/arm64/kernel/proton-pack.c:664) > [ 2105.281802][ T154] __switch_to (/home/anders/src/kernel/next/arch/arm64/kernel/process.c:459 /home/anders/src/kernel/next/arch/arm64/kernel/process.c:532) > [ 2105.284670][ T154] __schedule (/home/anders/src/kernel/next/kernel/sched/core.c:5247 /home/anders/src/kernel/next/kernel/sched/core.c:6555) > [ 2105.287555][ T154] preempt_schedule_irq (/home/anders/src/kernel/next/arch/arm64/include/asm/irqflags.h:70 /home/anders/src/kernel/next/arch/arm64/include/asm/irqflags.h:98 /home/anders/src/kernel/next/kernel/sched/core.c:6868) > [ 2105.290857][ T154] arm64_preempt_schedule_irq (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:237) > [ 2105.294433][ T154] el1_interrupt (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:476 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:486) > [ 2105.297433][ T154] el1h_64_irq_handler (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:492) > [ 2105.300718][ T154] el1h_64_irq (/home/anders/src/kernel/next/arch/arm64/kernel/entry.S:580) > [ 2105.303497][ T154] arch_local_irq_restore (/home/anders/src/kernel/next/arch/arm64/include/asm/jump_label.h:21 /home/anders/src/kernel/next/arch/arm64/include/asm/irqflags.h:130) > [ 2105.306750][ T154] fs_reclaim_acquire (/home/anders/src/kernel/next/mm/page_alloc.c:4691) > [ 2105.310118][ T154] slab_pre_alloc_hook.constprop.0 (/home/anders/src/kernel/next/include/linux/sched/mm.h:272 /home/anders/src/kernel/next/mm/slab.h:720) > [ 2105.313966][ T154] slab_alloc_node.isra.0 (/home/anders/src/kernel/next/mm/slub.c:3434) > [ 2105.317343][ T154] __kmem_cache_alloc_lru (/home/anders/src/kernel/next/mm/slub.c:3469) > [ 2105.320659][ T154] kmem_cache_alloc (/home/anders/src/kernel/next/mm/slub.c:3477) > [ 2105.323673][ T154] getname_flags (/home/anders/src/kernel/next/fs/namei.c:139) > [ 2105.326703][ T154] getname (/home/anders/src/kernel/next/fs/namei.c:218) > [ 2105.329377][ T154] do_sys_openat2 (/home/anders/src/kernel/next/fs/open.c:1304) > [ 2105.332352][ T154] __arm64_sys_openat (/home/anders/src/kernel/next/fs/open.c:1326) > [ 2105.335573][ T154] el0_svc_common.constprop.0 (/home/anders/src/kernel/next/arch/arm64/kernel/syscall.c:38 /home/anders/src/kernel/next/arch/arm64/kernel/syscall.c:52 /home/anders/src/kernel/next/arch/arm64/kernel/syscall.c:142) > [ 2105.339272][ T154] do_el0_svc (/home/anders/src/kernel/next/arch/arm64/kernel/syscall.c:197) > [ 2105.342025][ T154] el0_svc (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:133 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:142 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:638) > [ 2105.344687][ T154] el0t_64_sync_handler (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:656) > [ 2105.348089][ T154] el0t_64_sync (/home/anders/src/kernel/next/arch/arm64/kernel/entry.S:584) > [ 2105.350998][ T154] > [ 2105.352567][ T154] read to 0xffff8000210b3fb8 of 8 bytes by task 154 on cpu 0: > [ 2105.357117][ T154] do_page_fault (/home/anders/src/kernel/next/arch/arm64/mm/fault.c:517 /home/anders/src/kernel/next/arch/arm64/mm/fault.c:558) > [ 2105.360110][ T154] do_translation_fault (/home/anders/src/kernel/next/arch/arm64/mm/fault.c:695) > [ 2105.363400][ T154] do_mem_abort (/home/anders/src/kernel/next/arch/arm64/mm/fault.c:831) > [ 2105.366400][ T154] el0_ia (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:133 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:142 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:534) > [ 2105.369059][ T154] el0t_64_sync_handler (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:662) > [ 2105.372445][ T154] el0t_64_sync (/home/anders/src/kernel/next/arch/arm64/kernel/entry.S:584) > [ 2105.375404][ T154] > [ 2105.376935][ T154] no locks held by systemd/154. > [ 2105.379935][ T154] irq event stamp: 385 > [ 2105.382448][ T154] hardirqs last enabled at (385): local_daif_restore (/home/anders/src/kernel/next/arch/arm64/include/asm/daifflags.h:71 (discriminator 1)) > [ 2105.388413][ T154] hardirqs last disabled at (384): el0t_64_sync_handler (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:662) > [ 2105.394436][ T154] softirqs last enabled at (352): fpsimd_restore_current_state (/home/anders/src/kernel/next/arch/arm64/kernel/fpsimd.c:264 /home/anders/src/kernel/next/arch/arm64/kernel/fpsimd.c:1780) > [ 2105.400932][ T154] softirqs last disabled at (350): fpsimd_restore_current_state (/home/anders/src/kernel/next/include/linux/bottom_half.h:20 /home/anders/src/kernel/next/arch/arm64/kernel/fpsimd.c:242 /home/anders/src/kernel/next/arch/arm64/kernel/fpsimd.c:1773) > [ 2105.407394][ T154] > [ 2105.408909][ T154] value changed: 0x0000000060000000 -> 0x0000000060001000 > [ 2105.413225][ T154] > [ 2105.414746][ T154] Reported by Kernel Concurrency Sanitizer on: > [ 2105.426169][ T154] Hardware name: linux,dummy-virt (DT) > [ 2105.429528][ T154] ================================================================== > > > The prctl case, which only gets called on 'current'. However, assuming > the kernel could be preempted while accessing current->pt_regs->pstate, > and then it races against the task switch. > > Any idea what happens and how to fix it? I can't quite decipher this against mainline, as the line numbers above in do_page_fault() seem to correlate with reads of the esr, which is either a register or a stack read. I also think everything in the stacktraces is running in the context of 'current', so I can't see how we could really race here. :/ Will 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 99705C54E76 for ; Fri, 6 Jan 2023 17:39:35 +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=0LaJe8MjShtcjFbpemRofkEkjcaxjEt79s1T6Pei/y8=; b=NOnViyTs2u8Pfh gBdeE4UpsPjSGDAQfCuYWhCCXh3/y9IKht/m8ASrzTc0JPB88fwdmJfMQ724foZuDTbUYkiiGAo4M 7AzjRpDcPg4UrlFptE/DJ8h/9Tmii9apINQppOjm8QTtacOvUCHz+LMgcYsEsCTk6j8ojE2KwcXSJ c+If+kiUDG1CPQdNfkifjNA/qnIqB7sricRCmTSsgICBCaERyF1qvYkEu4jatz4977Ew05n0Dzdr4 uCAYzOV32NgAcXvkVxL5cBcAclWVdgZIey5tfK/0bDAwEsLb8LYH/ulGARwqQLC1MIeN9uOQKb3OL NpHIOKZtJcyEUzlUNrnw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pDqfk-00CMDP-9W; Fri, 06 Jan 2023 17:38:28 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pDqfg-00CLTj-Nc for linux-arm-kernel@lists.infradead.org; Fri, 06 Jan 2023 17:38:26 +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 ams.source.kernel.org (Postfix) with ESMTPS id 97688B810A7; Fri, 6 Jan 2023 17:38:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96A55C433EF; Fri, 6 Jan 2023 17:38:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673026700; bh=mVSb5WJNxb9CkrZLtlHqaTe+bEMhYwT0ZS0NE5kngJo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oPb9v8shkRWv2aUHwslq3X46cvS6dY8A7pPkMe1YRMrZjY+zzg1ecLol0MIE9yNAf J3EHogP5Z1HsWN5sNhF4uy7H4vGSQgMVfs8OrFhpp8GbzxgAbmqSEZ8WxqPEY4jxIE wyL5CXat6/M1HL9GflD3J6JcyU98X1n4XgVxM58N67CEg2L8KoyQlLZCmolEZWgAYL 3tFbUJ2eush/oWAfFtvDpb5Pho1roN5bhmFIeWxMMnSoVvL1V31ryaGWJZux6N//H1 6tbSJzqaJzyNdVEvmA+cYBeaqJLZ/78wDWiTAioAjy2soPiaL4R7U9TpD0nhmaeTbj n7mLWABL6ft8g== Date: Fri, 6 Jan 2023 17:38:15 +0000 From: Will Deacon To: Anders Roxell Cc: catalin.marinas@arm.com, mark.rutland@arm.com, james.morse@arm.com, ebiederm@xmission.com, elver@google.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, arnd@arndb.de Subject: Re: BUG: KCSAN: data-race in do_page_fault / spectre_v4_enable_task_mitigation Message-ID: <20230106173814.GA5169@willie-the-truck> References: <20221221145436.GF69385@mutt> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20221221145436.GF69385@mutt> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230106_093825_113721_9016945B X-CRM114-Status: GOOD ( 18.45 ) 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 21, 2022 at 03:54:36PM +0100, Anders Roxell wrote: > Hey, > > I'm building an allmodconfig kernel on yesterdays linux-next (tag: > next-20221220) and I see a > "BUG: KCSAN: data-race in do_page_fault / spectre_v4_enable_task_mitigation" > when I boot up in QEMU. I ran the output via > scripts/decode_stacktrace.sh and this is what I see: > > > [ 2105.261121][ T154] ================================================================== > [ 2105.266067][ T154] BUG: KCSAN: data-race in do_page_fault / spectre_v4_enable_task_mitigation > [ 2105.271577][ T154] > [ 2105.273121][ T154] write to 0xffff8000210b3fb8 of 8 bytes by task 136 on cpu 0: > [ 2105.277743][ T154] spectre_v4_enable_task_mitigation (/home/anders/src/kernel/next/arch/arm64/kernel/proton-pack.c:651 /home/anders/src/kernel/next/arch/arm64/kernel/proton-pack.c:664) > [ 2105.281802][ T154] __switch_to (/home/anders/src/kernel/next/arch/arm64/kernel/process.c:459 /home/anders/src/kernel/next/arch/arm64/kernel/process.c:532) > [ 2105.284670][ T154] __schedule (/home/anders/src/kernel/next/kernel/sched/core.c:5247 /home/anders/src/kernel/next/kernel/sched/core.c:6555) > [ 2105.287555][ T154] preempt_schedule_irq (/home/anders/src/kernel/next/arch/arm64/include/asm/irqflags.h:70 /home/anders/src/kernel/next/arch/arm64/include/asm/irqflags.h:98 /home/anders/src/kernel/next/kernel/sched/core.c:6868) > [ 2105.290857][ T154] arm64_preempt_schedule_irq (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:237) > [ 2105.294433][ T154] el1_interrupt (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:476 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:486) > [ 2105.297433][ T154] el1h_64_irq_handler (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:492) > [ 2105.300718][ T154] el1h_64_irq (/home/anders/src/kernel/next/arch/arm64/kernel/entry.S:580) > [ 2105.303497][ T154] arch_local_irq_restore (/home/anders/src/kernel/next/arch/arm64/include/asm/jump_label.h:21 /home/anders/src/kernel/next/arch/arm64/include/asm/irqflags.h:130) > [ 2105.306750][ T154] fs_reclaim_acquire (/home/anders/src/kernel/next/mm/page_alloc.c:4691) > [ 2105.310118][ T154] slab_pre_alloc_hook.constprop.0 (/home/anders/src/kernel/next/include/linux/sched/mm.h:272 /home/anders/src/kernel/next/mm/slab.h:720) > [ 2105.313966][ T154] slab_alloc_node.isra.0 (/home/anders/src/kernel/next/mm/slub.c:3434) > [ 2105.317343][ T154] __kmem_cache_alloc_lru (/home/anders/src/kernel/next/mm/slub.c:3469) > [ 2105.320659][ T154] kmem_cache_alloc (/home/anders/src/kernel/next/mm/slub.c:3477) > [ 2105.323673][ T154] getname_flags (/home/anders/src/kernel/next/fs/namei.c:139) > [ 2105.326703][ T154] getname (/home/anders/src/kernel/next/fs/namei.c:218) > [ 2105.329377][ T154] do_sys_openat2 (/home/anders/src/kernel/next/fs/open.c:1304) > [ 2105.332352][ T154] __arm64_sys_openat (/home/anders/src/kernel/next/fs/open.c:1326) > [ 2105.335573][ T154] el0_svc_common.constprop.0 (/home/anders/src/kernel/next/arch/arm64/kernel/syscall.c:38 /home/anders/src/kernel/next/arch/arm64/kernel/syscall.c:52 /home/anders/src/kernel/next/arch/arm64/kernel/syscall.c:142) > [ 2105.339272][ T154] do_el0_svc (/home/anders/src/kernel/next/arch/arm64/kernel/syscall.c:197) > [ 2105.342025][ T154] el0_svc (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:133 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:142 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:638) > [ 2105.344687][ T154] el0t_64_sync_handler (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:656) > [ 2105.348089][ T154] el0t_64_sync (/home/anders/src/kernel/next/arch/arm64/kernel/entry.S:584) > [ 2105.350998][ T154] > [ 2105.352567][ T154] read to 0xffff8000210b3fb8 of 8 bytes by task 154 on cpu 0: > [ 2105.357117][ T154] do_page_fault (/home/anders/src/kernel/next/arch/arm64/mm/fault.c:517 /home/anders/src/kernel/next/arch/arm64/mm/fault.c:558) > [ 2105.360110][ T154] do_translation_fault (/home/anders/src/kernel/next/arch/arm64/mm/fault.c:695) > [ 2105.363400][ T154] do_mem_abort (/home/anders/src/kernel/next/arch/arm64/mm/fault.c:831) > [ 2105.366400][ T154] el0_ia (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:133 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:142 /home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:534) > [ 2105.369059][ T154] el0t_64_sync_handler (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:662) > [ 2105.372445][ T154] el0t_64_sync (/home/anders/src/kernel/next/arch/arm64/kernel/entry.S:584) > [ 2105.375404][ T154] > [ 2105.376935][ T154] no locks held by systemd/154. > [ 2105.379935][ T154] irq event stamp: 385 > [ 2105.382448][ T154] hardirqs last enabled at (385): local_daif_restore (/home/anders/src/kernel/next/arch/arm64/include/asm/daifflags.h:71 (discriminator 1)) > [ 2105.388413][ T154] hardirqs last disabled at (384): el0t_64_sync_handler (/home/anders/src/kernel/next/arch/arm64/kernel/entry-common.c:662) > [ 2105.394436][ T154] softirqs last enabled at (352): fpsimd_restore_current_state (/home/anders/src/kernel/next/arch/arm64/kernel/fpsimd.c:264 /home/anders/src/kernel/next/arch/arm64/kernel/fpsimd.c:1780) > [ 2105.400932][ T154] softirqs last disabled at (350): fpsimd_restore_current_state (/home/anders/src/kernel/next/include/linux/bottom_half.h:20 /home/anders/src/kernel/next/arch/arm64/kernel/fpsimd.c:242 /home/anders/src/kernel/next/arch/arm64/kernel/fpsimd.c:1773) > [ 2105.407394][ T154] > [ 2105.408909][ T154] value changed: 0x0000000060000000 -> 0x0000000060001000 > [ 2105.413225][ T154] > [ 2105.414746][ T154] Reported by Kernel Concurrency Sanitizer on: > [ 2105.426169][ T154] Hardware name: linux,dummy-virt (DT) > [ 2105.429528][ T154] ================================================================== > > > The prctl case, which only gets called on 'current'. However, assuming > the kernel could be preempted while accessing current->pt_regs->pstate, > and then it races against the task switch. > > Any idea what happens and how to fix it? I can't quite decipher this against mainline, as the line numbers above in do_page_fault() seem to correlate with reads of the esr, which is either a register or a stack read. I also think everything in the stacktraces is running in the context of 'current', so I can't see how we could really race here. :/ Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel