On Thu, 7 May 2015 15:09:23 -0700
Doug Anderson <dianders@xxxxxxxxxxxx> 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 <dianders@xxxxxxxxxxxx>
> ---
> 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 <linux/miscdevice.h>
> #include <linux/module.h>
> #include <linux/moduleparam.h>
> +#include <linux/mutex.h>
> #include <linux/notifier.h>
> #include <linux/of.h>
> #include <linux/pm.h>
> #include <linux/platform_device.h>
> #include <linux/reboot.h>
> -#include <linux/spinlock.h>
> #include <linux/timer.h>
> #include <linux/uaccess.h>
> #include <linux/watchdog.h>
> @@ -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 <jszhang@xxxxxxxxxxx>
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