From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752250AbbEHCoO (ORCPT ); Thu, 7 May 2015 22:44:14 -0400 Received: from mx0a-0016f401.pphosted.com ([67.231.148.174]:59179 "EHLO mx0a-0016f401.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751418AbbEHCoN (ORCPT ); Thu, 7 May 2015 22:44:13 -0400 Date: Fri, 8 May 2015 10:40:38 +0800 From: Jisheng Zhang To: Doug Anderson CC: "wim@iguana.be" , "linux@roeck-us.net" , "linux-watchdog@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] watchdog: dw_wdt: Use a mutex, not a spinlock Message-ID: <20150508104038.027a1808@xhacker> In-Reply-To: <1431036564-4189-1-git-send-email-dianders@chromium.org> References: <1431036564-4189-1-git-send-email-dianders@chromium.org> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.14.151,1.0.33,0.0.0000 definitions=2015-05-08_01:2015-05-07,2015-05-08,1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=7.0.1-1402240000 definitions=main-1505080034 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 7 May 2015 15:09:23 -0700 Doug Anderson wrote: > Right now the dw_wdt uses a spinlock to protect dw_wdt_open(). The > problem is that while holding the spinlock we call: > -> dw_wdt_set_top() > -> dw_wdt_top_in_seconds() > -> clk_get_rate() > -> clk_prepare_lock() > -> mutex_lock() > > Locking a mutex while holding a spinlock is not allowed and leads to > warnings like "BUG: spinlock wrong CPU on CPU#1", among other > problems. > > There's no reason to use a spinlock, so switch to a mutex. > > Signed-off-by: Doug Anderson > --- > drivers/watchdog/dw_wdt.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c > index d0bb949..3fa2f19 100644 > --- a/drivers/watchdog/dw_wdt.c > +++ b/drivers/watchdog/dw_wdt.c > @@ -30,12 +30,12 @@ > #include > #include > #include > +#include > #include > #include > #include > #include > #include > -#include > #include > #include > #include > @@ -61,7 +61,7 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started " > #define WDT_TIMEOUT (HZ / 2) > > static struct { > - spinlock_t lock; > + struct mutex lock; > void __iomem *regs; > struct clk *clk; > unsigned long in_use; > @@ -177,7 +177,7 @@ static int dw_wdt_open(struct inode *inode, struct file *filp) > /* Make sure we don't get unloaded. */ > __module_get(THIS_MODULE); > > - spin_lock(&dw_wdt.lock); > + mutex_lock(&dw_wdt.lock); > if (!dw_wdt_is_enabled()) { > /* > * The watchdog is not currently enabled. Set the timeout to > @@ -190,7 +190,7 @@ static int dw_wdt_open(struct inode *inode, struct file *filp) > > dw_wdt_set_next_heartbeat(); > > - spin_unlock(&dw_wdt.lock); > + mutex_unlock(&dw_wdt.lock); > > return nonseekable_open(inode, filp); > } > @@ -348,7 +348,7 @@ static int dw_wdt_drv_probe(struct platform_device *pdev) > if (ret) > return ret; > > - spin_lock_init(&dw_wdt.lock); > + mutex_init(&dw_wdt.lock); > > ret = misc_register(&dw_wdt_miscdev); > if (ret) Tested on marvell BG2Q SoC, no issue found. So Tested-by: Jisheng Zhang