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 7BB56EE4993 for ; Tue, 22 Aug 2023 09:15:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234209AbjHVJPk (ORCPT ); Tue, 22 Aug 2023 05:15:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56650 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234202AbjHVJPj (ORCPT ); Tue, 22 Aug 2023 05:15:39 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83DC7113; Tue, 22 Aug 2023 02:15:38 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1CC0F611BF; Tue, 22 Aug 2023 09:15:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ECD36C433C7; Tue, 22 Aug 2023 09:15:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692695737; bh=NaYhwuuLQL7D2HhPJrC7Hc7Nb5lI7cYzmX+Szyowccg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=zrs701lvRJ/UmAaj/jAYYQzjqsZ6Ms4zD3t2FMKHSbz0sfcg6LOnGQSHWRe9P2Afg aKb1UC/hPXqwjVQOpho8UPGaYJOY0WNKI50NIdd9YUGzb/hsSQSWMfCwqNqw8ELS0i Us4BrSzztpUOpKNSGFXiIj0XekUCawa+QWVNK2k0= Date: Tue, 22 Aug 2023 11:15:34 +0200 From: Greg Kroah-Hartman To: Muhammad Usama Anjum Cc: Jiri Slaby , Ingo Molnar , kernel@collabora.com, stable@vger.kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Subject: Re: [PATCH v2 RESEND] tty/sysrq: replace smp_processor_id() with get_cpu() Message-ID: <2023082259-blazer-charity-b58f@gregkh> References: <20230822090112.2601273-1-usama.anjum@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230822090112.2601273-1-usama.anjum@collabora.com> Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Tue, Aug 22, 2023 at 02:01:11PM +0500, Muhammad Usama Anjum wrote: > The smp_processor_id() shouldn't be called from preemptible code. > Instead use get_cpu() and put_cpu() which disables preemption in > addition to getting the processor id. This fixes the following bug: > > [ 119.143590] sysrq: Show backtrace of all active CPUs > [ 119.143902] BUG: using smp_processor_id() in preemptible [00000000] code: bash/873 > [ 119.144586] caller is debug_smp_processor_id+0x20/0x30 > [ 119.144827] CPU: 6 PID: 873 Comm: bash Not tainted 5.10.124-dirty #3 > [ 119.144861] Hardware name: QEMU QEMU Virtual Machine, BIOS 2023.05-1 07/22/2023 > [ 119.145053] Call trace: > [ 119.145093] dump_backtrace+0x0/0x1a0 > [ 119.145122] show_stack+0x18/0x70 > [ 119.145141] dump_stack+0xc4/0x11c > [ 119.145159] check_preemption_disabled+0x100/0x110 > [ 119.145175] debug_smp_processor_id+0x20/0x30 > [ 119.145195] sysrq_handle_showallcpus+0x20/0xc0 > [ 119.145211] __handle_sysrq+0x8c/0x1a0 > [ 119.145227] write_sysrq_trigger+0x94/0x12c > [ 119.145247] proc_reg_write+0xa8/0xe4 > [ 119.145266] vfs_write+0xec/0x280 > [ 119.145282] ksys_write+0x6c/0x100 > [ 119.145298] __arm64_sys_write+0x20/0x30 > [ 119.145315] el0_svc_common.constprop.0+0x78/0x1e4 > [ 119.145332] do_el0_svc+0x24/0x8c > [ 119.145348] el0_svc+0x10/0x20 > [ 119.145364] el0_sync_handler+0x134/0x140 > [ 119.145381] el0_sync+0x180/0x1c0 > > Cc: stable@vger.kernel.org > Fixes: 47cab6a722d4 ("debug lockups: Improve lockup detection, fix generic arch fallback") > Signed-off-by: Muhammad Usama Anjum > --- > Changes since v1: > - Add "Cc: stable@vger.kernel.org" tag > --- This is not a resend, it is a new version, v3. Otherwise I would be confused with the original v2 which is different than this one... thanks, greg k-h