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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E66E0C33CA1 for ; Tue, 7 Jan 2020 21:15:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BAFA82072A for ; Tue, 7 Jan 2020 21:15:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729387AbgAGVIl (ORCPT ); Tue, 7 Jan 2020 16:08:41 -0500 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:37159 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729389AbgAGVIf (ORCPT ); Tue, 7 Jan 2020 16:08:35 -0500 Received: from callcc.thunk.org (guestnat-104-133-0-111.corp.google.com [104.133.0.111] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 007L7OUj026037 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 7 Jan 2020 16:07:27 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id BA95E4207DF; Tue, 7 Jan 2020 16:07:24 -0500 (EST) Date: Tue, 7 Jan 2020 16:07:24 -0500 From: "Theodore Y. Ts'o" To: Qian Cai Cc: arnd@arndb.de, gregkh@linuxfoundation.org, sergey.senozhatsky.work@gmail.com, pmladek@suse.com, rostedt@goodmis.org, catalin.marinas@arm.com, will@kernel.org, dan.j.williams@intel.com, peterz@infradead.org, longman@redhat.com, tglx@linutronix.de, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] char/random: silence a lockdep splat with printk() Message-ID: <20200107210724.GN3619@mit.edu> References: <1573679785-21068-1-git-send-email-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1573679785-21068-1-git-send-email-cai@lca.pw> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 13, 2019 at 04:16:25PM -0500, Qian Cai wrote: > From: Sergey Senozhatsky > > Sergey didn't like the locking order, > > uart_port->lock -> tty_port->lock > > uart_write (uart_port->lock) > __uart_start > pl011_start_tx > pl011_tx_chars > uart_write_wakeup > tty_port_tty_wakeup > tty_port_default > tty_port_tty_get (tty_port->lock) > > but those code is so old, and I have no clue how to de-couple it after > checking other locks in the splat. There is an onging effort to make all > printk() as deferred, so until that happens, workaround it for now as a > short-term fix. Applied, thanks. - Ted