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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 8B2AFC433E1 for ; Tue, 18 Aug 2020 12:52:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 67C2820706 for ; Tue, 18 Aug 2020 12:52:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726754AbgHRMwd (ORCPT ); Tue, 18 Aug 2020 08:52:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:51638 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726779AbgHRMwV (ORCPT ); Tue, 18 Aug 2020 08:52:21 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id E3F9BAE25; Tue, 18 Aug 2020 12:52:44 +0000 (UTC) Date: Tue, 18 Aug 2020 14:52:18 +0200 From: Petr Mladek To: Andy Shevchenko Cc: Sergey Senozhatsky , Greg KH , Guenter Roeck , Tony Lindgren , Kurt Kanzenbach , Raul Rangel , Steven Rostedt , John Ogness , linux-kernel , linux-serial@vger.kernel.org Subject: Re: [PATCH] uart:8250: change lock order in serial8250_do_startup() Message-ID: <20200818125218.GC17612@alley> References: <20200814013802.357412-1-sergey.senozhatsky@gmail.com> <20200814095928.GK1891694@smile.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200814095928.GK1891694@smile.fi.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Fri 2020-08-14 12:59:28, Andy Shevchenko wrote: > On Fri, Aug 14, 2020 at 10:38:02AM +0900, Sergey Senozhatsky wrote: > > We have a number of "uart.port->desc.lock vs desc.lock->uart.port" > > lockdep reports coming from 8250 driver; this causes a bit of trouble > > to people, so let's fix it. > > > > I guess we may add some tags here > > Fixes: 768aec0b5bcc ("serial: 8250: fix shared interrupts issues with SMP and RT kernels") > Reported-by: Guenter Roeck > Reported-by: Raul Rangel > BugLink: https://bugs.chromium.org/p/chromium/issues/detail?id=1114800 > Link: https://lore.kernel.org/lkml/CAHQZ30BnfX+gxjPm1DUd5psOTqbyDh4EJE=2=VAMW_VDafctkA@mail.gmail.com/T/#u "Link:" tag should point to the mail that is applied using git am. I am not sure if there is a tag for related discussion in another mail threads. A solution might be to add a comment like: This solution has been discussed in several threads: https://lore.kernel.org/lkml/CAHQZ30BnfX+gxjPm1DUd5psOTqbyDh4EJE=2=VAMW_VDafctkA@mail.gmail.com/T/#u https://lore.kernel.org/lkml/20200812154813.GA46894@roeck-us.net/#t > > --- a/drivers/tty/serial/8250/8250_port.c > > +++ b/drivers/tty/serial/8250/8250_port.c > > @@ -2275,6 +2275,11 @@ int serial8250_do_startup(struct uart_port *port) > > > > if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) { > > unsigned char iir1; > > > + bool irq_shared = up->port.irqflags & IRQF_SHARED; > > I'm wondering why we need a temporary variable? This flag is not supposed to be > changed in between, can we leave original conditionals? > > Nevertheless I noticed an inconsistency of the dereference of the flags which > seems to be brough by dfe42443ea1d ("serial: reduce number of indirections in > 8250 code"). > > I think we can stick with newer: > > if (port->irqflags & IRQF_SHARED) Sounds reasonable to me. Andy proposed many changes. Sergey, could you please send v2? Best Regards, Petr