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 C95F6EE4993 for ; Tue, 22 Aug 2023 10:27:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233492AbjHVK11 (ORCPT ); Tue, 22 Aug 2023 06:27:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233554AbjHVK11 (ORCPT ); Tue, 22 Aug 2023 06:27:27 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 04F79CC8; Tue, 22 Aug 2023 03:27:23 -0700 (PDT) Received: from [192.168.10.12] (unknown [39.45.215.81]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: usama.anjum) by madras.collabora.co.uk (Postfix) with ESMTPSA id AE4FD6607215; Tue, 22 Aug 2023 11:27:19 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1692700042; bh=2DBcZcOC3jRRssDkdf7QwArSMcaYykvUqxjA+hZileU=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=Wn1oBb7N4ywT0/KiEWpkGF11gZ0GBXnPSlboUu9e7wICvdsVWI1tin1HHK5HoeHRC HyZ5kzANcQ51kt06kU886Ke3OzVPqsXIntnzhAm/32TR/YoGbnhuLl8DofIUZLdEpN wfgbNrr4pG95nnp1oB5t7fsugtJlMmY9CKHYNZLETsTFo+HWSzjQXK+itVBhHkaZDW vuGn2IP5Xkbk7X47q+I1tc+WIKapJhVnY9s6EtMV+ij4EEumBcynvks2+TZgWfOSMq hVa0/3FuKhZ4Vx+pGDRaFkJuwDwuNHvgb+4yAwaGQbs2rchSpp3pmyOkWS9Dd4olbf 7KPXgZW+OAXoQ== Message-ID: <1786e05a-300a-4259-be1e-2cc54db9c16b@collabora.com> Date: Tue, 22 Aug 2023 15:27:15 +0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: Muhammad Usama Anjum , 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() Content-Language: en-US To: Greg Kroah-Hartman References: <20230822090112.2601273-1-usama.anjum@collabora.com> <2023082259-blazer-charity-b58f@gregkh> From: Muhammad Usama Anjum In-Reply-To: <2023082259-blazer-charity-b58f@gregkh> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On 8/22/23 2:15 PM, Greg Kroah-Hartman wrote: > 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... Sorry, didn't relaize this. I've sent this as v3: https://lore.kernel.org/all/20230822102606.2821311-1-usama.anjum@collabora.com > > thanks, > > greg k-h -- BR, Muhammad Usama Anjum