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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 9B4EBC43461 for ; Mon, 12 Apr 2021 13:08:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 686EA6128A for ; Mon, 12 Apr 2021 13:08:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241698AbhDLNIk (ORCPT ); Mon, 12 Apr 2021 09:08:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:35458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241676AbhDLNIi (ORCPT ); Mon, 12 Apr 2021 09:08:38 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3A16F6128A; Mon, 12 Apr 2021 13:08:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618232900; bh=+gF3uqIXavl3hMrOghe8B0SiT2ksN2Qd1LhyosV53go=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SbwiRoVspb29bqg8e/3ppeaDXykbxSHRBpjaDlHedmqky9OuVKYGfU3+c3qEwtQB/ gpUXRcx61QcRWRRWz6EQn60j5b8JdfYghszN3CX+xsEUD87zvoc1XuW4mdE94mZaZu cqwjVI6U3iAtRxfTarN0XoPpYuCuqoBSOJF0qZMbjdatOwk3YvIjvbG2UsqzPdKN5a kxAO92d66Rh2P7xnc3H6e/3RHYmjSODNglm9AvxdeWgmwEvbiFh0dBzqUq4t57O6JI JLSvw906nSA5ARIIwKaXsM7XGBcp2so24ZzU+aT40aE+14K9lx/w3CD5ZjEzPZ6tYQ u+9JefcIQGTyA== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lVwIY-00028W-Bh; Mon, 12 Apr 2021 15:08:14 +0200 Date: Mon, 12 Apr 2021 15:08:14 +0200 From: Johan Hovold To: dillon.minfei@gmail.com Cc: gregkh@linuxfoundation.org, jirislaby@kernel.org, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, lkp@intel.com, linux-serial@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kbuild-all@lists.01.org, clang-built-linux@googlegroups.com, Gerald Baeza , Erwan Le Ray Subject: Re: [PATCH v2] serial: stm32: optimize spin lock usage Message-ID: References: <1618219898-4600-1-git-send-email-dillon.minfei@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1618219898-4600-1-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 05:31:38PM +0800, dillon.minfei@gmail.com wrote: > From: dillon min > > To avoid potential deadlock in spin_lock usage, use spin_lock_irqsave, > spin_trylock_irqsave(), spin_unlock_irqrestore() in process context. This doesn't make much sense as console_write can be called in any context. And where's the deadlock you claim to be fixing here? > remove unused local_irq_save/restore call. > > Cc: Alexandre Torgue > Cc: Maxime Coquelin > Cc: Gerald Baeza > Cc: Erwan Le Ray > Reported-by: kernel test robot > Signed-off-by: dillon min > --- > v2: remove unused code from stm32_usart_threaded_interrupt() according from > Greg's review. > > drivers/tty/serial/stm32-usart.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c > index b3675cf25a69..b1ba5e36e36e 100644 > --- a/drivers/tty/serial/stm32-usart.c > +++ b/drivers/tty/serial/stm32-usart.c > @@ -1354,13 +1354,12 @@ static void stm32_usart_console_write(struct console *co, const char *s, > u32 old_cr1, new_cr1; > int locked = 1; > > - local_irq_save(flags); > if (port->sysrq) > locked = 0; > else if (oops_in_progress) > - locked = spin_trylock(&port->lock); > + locked = spin_trylock_irqsave(&port->lock, flags); > else > - spin_lock(&port->lock); > + spin_lock_irqsave(&port->lock, flags); > > /* Save and disable interrupts, enable the transmitter */ > old_cr1 = readl_relaxed(port->membase + ofs->cr1); > @@ -1374,8 +1373,7 @@ static void stm32_usart_console_write(struct console *co, const char *s, > writel_relaxed(old_cr1, port->membase + ofs->cr1); > > if (locked) > - spin_unlock(&port->lock); > - local_irq_restore(flags); > + spin_unlock_irqrestore(&port->lock, flags); > } > > static int stm32_usart_console_setup(struct console *co, char *options) Johan