From patchwork Tue Oct 27 13:50:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 312577 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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 DB417C388F9 for ; Tue, 27 Oct 2020 15:34:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8D20822265 for ; Tue, 27 Oct 2020 15:34:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603812859; bh=/DJbkGWZe5025wo5u4bMwrhCrwpohauIKQ6UXOkJg/M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=kTkNi99pYFVBEAw7URf496IL+acuMRJYFsYYUQJbrPRLcb3uOIzDTOS7bkSh8077i zRrTieRSHO/yPx0bTdhVbyN/GBJcVJuBGRRzz/Y5MpgZNeVtMdHbFE6B8frodJwpWd OJKkPVwScJXJDU+pfmdUqwgMZPCZU3twx4KqxI2Q= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1798444AbgJ0PeS (ORCPT ); Tue, 27 Oct 2020 11:34:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:52264 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1799944AbgJ0PeP (ORCPT ); Tue, 27 Oct 2020 11:34:15 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DBD4622264; Tue, 27 Oct 2020 15:34:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603812854; bh=/DJbkGWZe5025wo5u4bMwrhCrwpohauIKQ6UXOkJg/M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DRLBsHKp6RT1lYEZz61NiMqv2dtV1e0SFCmaYOfqhIZmCcIuDkQ+8Y4x3BiRsk1K4 5K0uO6hHaiGKwQzoF9OzP65b7sI9YUSxhp/E6cXpfyeBuLX/4YTqNEoAId8WGur38g WMP+swHYSUmoxBXHY+4hQK+RnNsgbkUCdyAzhTmU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hans de Goede , Serge Semin , Sasha Levin Subject: [PATCH 5.9 354/757] serial: 8250_dw: Fix clk-notifier/port suspend deadlock Date: Tue, 27 Oct 2020 14:50:04 +0100 Message-Id: <20201027135507.180954087@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135450.497324313@linuxfoundation.org> References: <20201027135450.497324313@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Serge Semin [ Upstream commit 85985a3dcd7415dd849cf62ec14f931cd905099a ] It has been discovered that there is a potential deadlock between the clock-change-notifier thread and the UART port suspending one: CPU0 (suspend CPU/UART) CPU1 (update clock) ---- ---- lock(&port->mutex); lock((work_completion)(&data->clk_work)); lock(&port->mutex); lock((work_completion)(&data->clk_work)); *** DEADLOCK *** The best way to fix this is to eliminate the CPU0 port->mutex/work-completion scenario. So we suggest to register and unregister the clock-notifier during the DW APB UART port probe/remove procedures, instead of doing that at the points of the port startup/shutdown. Link: https://lore.kernel.org/linux-serial/f1cd5c75-9cda-6896-a4e2-42c5bfc3f5c3@redhat.com Fixes: cc816969d7b5 ("serial: 8250_dw: Fix common clocks usage race condition") Reported-by: Hans de Goede Tested-by: Hans de Goede Signed-off-by: Serge Semin Link: https://lore.kernel.org/r/20200923161950.6237-4-Sergey.Semin@baikalelectronics.ru Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/8250/8250_dw.c | 54 +++++++++++-------------------- 1 file changed, 19 insertions(+), 35 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 87f450b7c1779..9e204f9b799a1 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -373,39 +373,6 @@ static void dw8250_set_ldisc(struct uart_port *p, struct ktermios *termios) serial8250_do_set_ldisc(p, termios); } -static int dw8250_startup(struct uart_port *p) -{ - struct dw8250_data *d = to_dw8250_data(p->private_data); - int ret; - - /* - * Some platforms may provide a reference clock shared between several - * devices. In this case before using the serial port first we have to - * make sure that any clock state change is known to the UART port at - * least post factum. - */ - if (d->clk) { - ret = clk_notifier_register(d->clk, &d->clk_notifier); - if (ret) - dev_warn(p->dev, "Failed to set the clock notifier\n"); - } - - return serial8250_do_startup(p); -} - -static void dw8250_shutdown(struct uart_port *p) -{ - struct dw8250_data *d = to_dw8250_data(p->private_data); - - serial8250_do_shutdown(p); - - if (d->clk) { - clk_notifier_unregister(d->clk, &d->clk_notifier); - - flush_work(&d->clk_work); - } -} - /* * dw8250_fallback_dma_filter will prevent the UART from getting just any free * channel on platforms that have DMA engines, but don't have any channels @@ -501,8 +468,6 @@ static int dw8250_probe(struct platform_device *pdev) p->serial_out = dw8250_serial_out; p->set_ldisc = dw8250_set_ldisc; p->set_termios = dw8250_set_termios; - p->startup = dw8250_startup; - p->shutdown = dw8250_shutdown; p->membase = devm_ioremap(dev, regs->start, resource_size(regs)); if (!p->membase) @@ -622,6 +587,19 @@ static int dw8250_probe(struct platform_device *pdev) goto err_reset; } + /* + * Some platforms may provide a reference clock shared between several + * devices. In this case any clock state change must be known to the + * UART port at least post factum. + */ + if (data->clk) { + err = clk_notifier_register(data->clk, &data->clk_notifier); + if (err) + dev_warn(p->dev, "Failed to set the clock notifier\n"); + else + queue_work(system_unbound_wq, &data->clk_work); + } + platform_set_drvdata(pdev, data); pm_runtime_set_active(dev); @@ -648,6 +626,12 @@ static int dw8250_remove(struct platform_device *pdev) pm_runtime_get_sync(dev); + if (data->clk) { + clk_notifier_unregister(data->clk, &data->clk_notifier); + + flush_work(&data->clk_work); + } + serial8250_unregister_port(data->data.line); reset_control_assert(data->rst);