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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 475C2C43460 for ; Mon, 12 Apr 2021 05:52:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C3C9600EF for ; Mon, 12 Apr 2021 05:52:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230345AbhDLFwp (ORCPT ); Mon, 12 Apr 2021 01:52:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:44276 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229482AbhDLFwo (ORCPT ); Mon, 12 Apr 2021 01:52:44 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A75D561207; Mon, 12 Apr 2021 05:52:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1618206747; bh=efCpCnAinHSf2kSKdV1JoeqCUQSQ/06SRXMJwGOgVdc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oWgropJxyAI8fh04gSOaCZDSUtj00UIEqrA1HMKf54YVJLlfVfGzlIZqRmMH29h3M 8n0DXpGk0AvcvVsvIHvGkfwhG/VKqdkHNdNwefP4EvhPkyBWbuqo+E8DpqppwZea74 asFZk45SAuqLMKJGYJ4+CtCiT44m331SXxTo8ylU= Date: Mon, 12 Apr 2021 07:52:24 +0200 From: Greg KH To: dillon.minfei@gmail.com Cc: jirislaby@kernel.org, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, linux-serial@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] serial: stm32: optimize spin lock usage Message-ID: References: <1618202061-8243-1-git-send-email-dillon.minfei@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1618202061-8243-1-git-send-email-dillon.minfei@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 12, 2021 at 12:34:21PM +0800, dillon.minfei@gmail.com wrote: > From: dillon min > > To avoid potential deadlock in spin_lock usage, change to use > spin_lock_irqsave(), spin_unlock_irqrestore() in process(thread_fn) context. > spin_lock(), spin_unlock() under handler context. > > remove unused local_irq_save/restore call. > > Signed-off-by: dillon min > --- > Was verified on stm32f469-disco board. need more test on stm32mp platform. > > drivers/tty/serial/stm32-usart.c | 27 +++++++++++++++++---------- > 1 file changed, 17 insertions(+), 10 deletions(-) > > diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c > index b3675cf25a69..c4c859b34367 100644 > --- a/drivers/tty/serial/stm32-usart.c > +++ b/drivers/tty/serial/stm32-usart.c > @@ -214,7 +214,7 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded) > struct tty_port *tport = &port->state->port; > struct stm32_port *stm32_port = to_stm32_port(port); > const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; > - unsigned long c; > + unsigned long c, flags; > u32 sr; > char flag; > > @@ -276,9 +276,17 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded) > uart_insert_char(port, sr, USART_SR_ORE, c, flag); > } > > - spin_unlock(&port->lock); > + if (threaded) > + spin_unlock_irqrestore(&port->lock, flags); > + else > + spin_unlock(&port->lock); You shouldn't have to check for this, see the other patches on the list recently that fixed this up to not be an issue for irq handlers. thanks, greg k-h