[WATCHDOG] w836?7hf_wdt spinlock fixes.

Add io spinlocks to prevent possible race
conditions between start and stop operations
that are issued from different child processes
where the master process opened /dev/watchdog.

Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/char/watchdog/w83697hf_wdt.c b/drivers/char/watchdog/w83697hf_wdt.c
index ef6612e1b91f..21e822e0eeec 100644
--- a/drivers/char/watchdog/w83697hf_wdt.c
+++ b/drivers/char/watchdog/w83697hf_wdt.c
@@ -33,6 +33,7 @@
 #include <linux/notifier.h>
 #include <linux/reboot.h>
 #include <linux/init.h>
+#include <linux/spinlock.h>
 
 #include <asm/io.h>
 #include <asm/uaccess.h>
@@ -44,6 +45,7 @@
 
 static unsigned long wdt_is_open;
 static char expect_close;
+static spinlock_t io_lock;
 
 /* You must set this - there is no sane way to probe for this board. */
 static int wdt_io = 0x2E;
@@ -114,12 +116,16 @@ w83697hf_init(void)
 static void
 wdt_ctrl(int timeout)
 {
+        spin_lock(&io_lock);
+
         w83697hf_select_wd_register();
 
         outb_p(0xF4, WDT_EFER);    /* Select CRF4 */
         outb_p(timeout, WDT_EFDR); /* Write Timeout counter to CRF4 */
 
         w83697hf_unselect_wd_register();
+
+        spin_unlock(&io_lock);
 }
 
 static int
@@ -307,6 +313,8 @@ wdt_init(void)
 {
         int ret;
 
+        spin_lock_init(&io_lock);
+
         printk(KERN_INFO "WDT driver for the Winbond(TM) W83697HF Super I/O chip initialising.\n");
 
         if (wdt_set_heartbeat(timeout)) {