watchdog: dw_wdt: No need for a spinlock
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. Only dw_wdt_open() was protected
and the test_and_set_bit() at the start of that function protects us
anyway.
Signed-off-by: Doug Anderson <dianders@chromium.org>
Tested-by: Jisheng Zhang <jszhang@marvell.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
index d0bb949..a284abd 100644
--- a/drivers/watchdog/dw_wdt.c
+++ b/drivers/watchdog/dw_wdt.c
@@ -35,7 +35,6 @@
#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 +60,6 @@
#define WDT_TIMEOUT (HZ / 2)
static struct {
- spinlock_t lock;
void __iomem *regs;
struct clk *clk;
unsigned long in_use;
@@ -177,7 +175,6 @@
/* Make sure we don't get unloaded. */
__module_get(THIS_MODULE);
- spin_lock(&dw_wdt.lock);
if (!dw_wdt_is_enabled()) {
/*
* The watchdog is not currently enabled. Set the timeout to
@@ -190,8 +187,6 @@
dw_wdt_set_next_heartbeat();
- spin_unlock(&dw_wdt.lock);
-
return nonseekable_open(inode, filp);
}
@@ -348,8 +343,6 @@
if (ret)
return ret;
- spin_lock_init(&dw_wdt.lock);
-
ret = misc_register(&dw_wdt_miscdev);
if (ret)
goto out_disable_clk;