Make all it87 drivers SMP safe

01 - Changes to it87 watchdog driver to use "request_muxed_region" Serialize access to the hardware by using "request_muxed_region" macro defined by Alan Cox. Call to this macro will hold off the requestor if the resource is currently busy.

The use of the above macro makes it possible to get rid of spinlocks in it8712f_wdt.c and it87_wdt.c watchdog drivers. This also greatly simplifies the implementation of it87_wdt.c driver.

"superio_enter" will return an error if call to "request_muxed_region" fails.
Rest of the code change is to ripple an error return from superio_enter to the top level.

Signed-off-by Nat Gurumoorthy <[email protected]>

---

drivers/watchdog/it8712f_wdt.c +16 -6

index 6143f52..0442889 100644
@@ -51,7 +51,6 @@ MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");
 
 static unsigned long wdt_open;
 static unsigned expect_close;
-static spinlock_t io_lock;
 static unsigned char revision;
 
 /* Dog Food address - We use the game port address */

@@ -121,20 +120,27 @@ static inline void superio_select(int ldn)
        outb(ldn, VAL);
 }
 
-static inline void superio_enter(void)
+static inline int
+superio_enter(void)
 {
-       spin_lock(&io_lock);
+       /*
+        * Try to reserve REG and REG + 1 for exclusive access.
+        */
+       if (!request_muxed_region(REG, 2, NAME))
+               return -EBUSY;
+
        outb(0x87, REG);
        outb(0x01, REG);
        outb(0x55, REG);
        outb(0x55, REG);
+       return 0;
 }
 
 static inline void superio_exit(void)
 {
        outb(0x02, REG);
        outb(0x02, VAL);
-       spin_unlock(&io_lock);
+       release_region(REG, 2);
 }
 
 static inline void it8712f_wdt_ping(void)

@@ -173,10 +179,12 @@ static int it8712f_wdt_get_status(void)
                return 0;
 }
 
-static void it8712f_wdt_enable(void)
+static int it8712f_wdt_enable(void)
 {
        printk(KERN_DEBUG NAME ": enabling watchdog timer\n");
-       superio_enter();
+       if (superio_enter())
+               return -EBUSY;
+
        superio_select(LDN_GPIO);
 
        superio_outb(wdt_control_reg, WDT_CONTROL);

@@ -186,13 +194,17 @@ static void it8712f_wdt_enable(void)
        superio_exit();
 
        it8712f_wdt_ping();
+
+       return 0;

drivers/watchdog/it8712f_wdt.c +2 -0

+
        superio_select(LDN_GPIO);
 
        superio_outb(0, WDT_CONFIG);

@@ -202,6 +214,7 @@ static void it8712f_wdt_disable(void)
        superio_outb(0, WDT_TIMEOUT);
 
        superio_exit();
+       return 0;
 }
 
 static int it8712f_wdt_notify(struct notifier_block *this,

drivers/watchdog/it8712f_wdt.c +13 -8

        return NOTIFY_DONE;
 }

@@ -259,7 +273,8 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
                        return -EFAULT;
                return 0;
        case WDIOC_GETSTATUS:
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
                superio_select(LDN_GPIO);
 
                value = it8712f_wdt_get_status();

@@ -280,7 +295,8 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
                if (value > (max_units * 60))
                        return -EINVAL;
                margin = value;
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
                superio_select(LDN_GPIO);
 
                it8712f_wdt_update_margin();

@@ -302,7 +318,8 @@ static int it8712f_wdt_open(struct inode *inode, struct file *file)
        /* only allow one at a time */
        if (test_and_set_bit(0, &wdt_open))
                return -EBUSY;
-       it8712f_wdt_enable();
+       if (it8712f_wdt_enable())
+               return -EBUSY;
        return nonseekable_open(inode, file);
 }
 

@@ -313,7 +330,8 @@ static int it8712f_wdt_release(struct inode *inode, struct file *file)
                        ": watchdog device closed unexpectedly, will not"
                        " disable the watchdog timer\n");
        } else if (!nowayout) {
-               it8712f_wdt_disable();
+               if (it8712f_wdt_disable())
+                       return -EBUSY;
        }
        expect_close = 0;
        clear_bit(0, &wdt_open);

@@ -341,7 +359,9 @@ static int __init it8712f_wdt_find(unsigned short *address)
        int err = -ENODEV;
        int chip_type;
 
-       superio_enter();
+       if (superio_enter())
+               return -EBUSY;
+
        chip_type = superio_inw(DEVID);
        if (chip_type != IT8712F_DEVID)
                goto exit;

@@ -382,8 +402,6 @@ static int __init it8712f_wdt_init(void)
 {
        int err = 0;
 
-       spin_lock_init(&io_lock);
-
        if (it8712f_wdt_find(&address))
                return -ENODEV;
 

@@ -392,7 +410,8 @@ static int __init it8712f_wdt_init(void)
                return -EBUSY;
        }
 
-       it8712f_wdt_disable();
+       if (it8712f_wdt_disable())
+               return -EBUSY;
 
        err = register_reboot_notifier(&it8712f_wdt_notifier);
        if (err) {

drivers/watchdog/it87_wdt.c +19 -16

index b1bc72f..39c98cb 100644
@@ -137,7 +137,6 @@
 
 static unsigned int base, gpact, ciract, max_units, chip_type;
 static unsigned long wdt_status;
-static DEFINE_SPINLOCK(spinlock);
 
 static int nogameport = DEFAULT_NOGAMEPORT;
 static int exclusive  = DEFAULT_EXCLUSIVE;

@@ -163,18 +162,27 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started, default="
 
 /* Superio Chip */
 
-static inline void superio_enter(void)
+static inline int
+superio_enter(void)
 {
+       /*
+        * Try to reserve REG and REG + 1 for exclusive access.
+        */
+       if (!request_muxed_region(REG, 2, WATCHDOG_NAME))
+               return -EBUSY;
+
        outb(0x87, REG);
        outb(0x01, REG);
        outb(0x55, REG);
        outb(0x55, REG);
+       return 0;
 }
 
 static inline void superio_exit(void)
 {
        outb(0x02, REG);
        outb(0x02, VAL);
+       release_region(REG, 2);
 }
 
 static inline void superio_select(int ldn)

@@ -255,12 +263,10 @@ static void wdt_keepalive(void)
        set_bit(WDTS_KEEPALIVE, &wdt_status);
 }
 
-static void wdt_start(void)
+static int wdt_start(void)
 {
-       unsigned long flags;
-
-       spin_lock_irqsave(&spinlock, flags);
-       superio_enter();
+       if (superio_enter())
+               return -EBUSY;
 
        superio_select(GPIO);
        if (test_bit(WDTS_USE_GP, &wdt_status))

@@ -270,15 +276,14 @@ static void wdt_start(void)
        wdt_update_timeout();
 
        superio_exit();
-       spin_unlock_irqrestore(&spinlock, flags);
+
+       return 0;
 }
 
-static void wdt_stop(void)
+static int wdt_stop(void)
 {
-       unsigned long flags;
-
-       spin_lock_irqsave(&spinlock, flags);
-       superio_enter();
+       if (superio_enter())
+               return -EBUSY;
 
        superio_select(GPIO);
        superio_outb(0x00, WDTCTRL);

@@ -288,7 +293,7 @@ static void wdt_stop(void)
                superio_outb(0x00, WDTVALMSB);
 
        superio_exit();
-       spin_unlock_irqrestore(&spinlock, flags);
+       return 0;
 }
 
 /**

@@ -303,8 +308,6 @@ static void wdt_stop(void)
 
 static int wdt_set_timeout(int t)
 {
-       unsigned long flags;
-
        if (t < 1 || t > max_units * 60)
                return -EINVAL;
 

drivers/watchdog/it87_wdt.c +28 -12

                superio_select(GPIO);
                wdt_update_timeout();
                superio_exit();
        }
-       spin_unlock_irqrestore(&spinlock, flags);
        return 0;
 }
 

@@ -339,12 +342,10 @@ static int wdt_set_timeout(int t)
 
 static int wdt_get_status(int *status)
 {
-       unsigned long flags;
-
        *status = 0;
        if (testmode) {
-               spin_lock_irqsave(&spinlock, flags);
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
                superio_select(GPIO);
                if (superio_inb(WDTCTRL) & WDT_ZERO) {
                        superio_outb(0x00, WDTCTRL);

@@ -353,7 +354,6 @@ static int wdt_get_status(int *status)
                }
 
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
        }
        if (test_and_clear_bit(WDTS_KEEPALIVE, &wdt_status))
                *status |= WDIOF_KEEPALIVEPING;

@@ -381,7 +381,12 @@ static int wdt_open(struct inode *inode, struct file *file)
        if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status)) {
                if (nowayout && !test_and_set_bit(WDTS_LOCKED, &wdt_status))
                        __module_get(THIS_MODULE);
-               wdt_start();
+               if (wdt_start()) {
+                       clear_bit(WDTS_LOCKED, &wdt_status);
+                       clear_bit(WDTS_TIMER_RUN, &wdt_status);
+                       clear_bit(WDTS_DEV_OPEN, &wdt_status);
+                       return -EBUSY;
+               }
        }
        return nonseekable_open(inode, file);
 }

@@ -403,7 +408,15 @@ static int wdt_release(struct inode *inode, struct file *file)
 {
        if (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
                if (test_and_clear_bit(WDTS_EXPECTED, &wdt_status)) {
-                       wdt_stop();
+                       if (wdt_stop()) {
+                               /*
+                                * Stop failed. Just keep the watchdog alive
+                                * and hope nothing bad happens.
+                                */
+                               set_bit(WDTS_EXPECTED, &wdt_status);
+                               wdt_keepalive();
+                               return -EBUSY;
+                       }
                        clear_bit(WDTS_TIMER_RUN, &wdt_status);
                } else {
                        wdt_keepalive();

@@ -484,7 +497,8 @@ static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                                    &ident, sizeof(ident)) ? -EFAULT : 0;
 
        case WDIOC_GETSTATUS:
-               wdt_get_status(&status);
+               if (wdt_get_status(&status))
+                       return -EBUSY;
                return put_user(status, uarg.i);
 
        case WDIOC_GETBOOTSTATUS:

@@ -501,13 +515,19 @@ static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                switch (new_options) {
                case WDIOS_DISABLECARD:
                        if (test_bit(WDTS_TIMER_RUN, &wdt_status))
-                               wdt_stop();
+                               if (wdt_stop())
+                                       return -EBUSY;
+
                        clear_bit(WDTS_TIMER_RUN, &wdt_status);
                        return 0;
 
                case WDIOS_ENABLECARD:
-                       if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status))
-                               wdt_start();
+                       if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status)) {
+                               if (wdt_start()) {
+                                       clear_bit(WDTS_TIMER_RUN, &wdt_status);
+                                       return -EBUSY;
+                               }
+                       }
                        return 0;
 
                default:

drivers/watchdog/it87_wdt.c +11 -17

        return NOTIFY_DONE;
 }
 

@@ -560,16 +581,15 @@ static int __init it87_wdt_init(void)
        int rc = 0;
        int try_gameport = !nogameport;
        u8  chip_rev;
-       unsigned long flags;
 
        wdt_status = 0;
 
-       spin_lock_irqsave(&spinlock, flags);
-       superio_enter();
+       if (superio_enter())
+               return -EBUSY;
+
        chip_type = superio_inw(CHIPID);
        chip_rev  = superio_inb(CHIPREV) & 0x0f;
        superio_exit();
-       spin_unlock_irqrestore(&spinlock, flags);
 
        switch (chip_type) {
        case IT8702_ID:

@@ -603,8 +623,8 @@ static int __init it87_wdt_init(void)
                return -ENODEV;
        }
 
-       spin_lock_irqsave(&spinlock, flags);
-       superio_enter();
+       if (superio_enter())
+               return -EBUSY;
 
        superio_select(GPIO);
        superio_outb(WDT_TOV1, WDTCFG);

@@ -621,14 +641,12 @@ static int __init it87_wdt_init(void)
                gpact = superio_inb(ACTREG);
                superio_outb(0x01, ACTREG);
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
                if (request_region(base, 1, WATCHDOG_NAME))
                        set_bit(WDTS_USE_GP, &wdt_status);
                else
                        rc = -EIO;
        } else {
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
        }
 
        /* If we haven't Gameport support, try to get CIR support */

@@ -646,8 +664,8 @@ static int __init it87_wdt_init(void)
                        goto err_out;
                }
                base = CIR_BASE;
-               spin_lock_irqsave(&spinlock, flags);
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
 
                superio_select(CIR);
                superio_outw(base, BASEREG);

@@ -660,7 +678,6 @@ static int __init it87_wdt_init(void)
                }
 
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
        }
 
        if (timeout < 1 || timeout > max_units * 60) {

@@ -711,21 +728,19 @@ err_out_reboot:
 err_out_region:
        release_region(base, test_bit(WDTS_USE_GP, &wdt_status) ? 1 : 8);
        if (!test_bit(WDTS_USE_GP, &wdt_status)) {
-               spin_lock_irqsave(&spinlock, flags);
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
                superio_select(CIR);
                superio_outb(ciract, ACTREG);
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
        }
 err_out:
        if (try_gameport) {
-               spin_lock_irqsave(&spinlock, flags);
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
                superio_select(GAMEPORT);
                superio_outb(gpact, ACTREG);
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
        }
 
        return rc;

drivers/watchdog/it87_wdt.c +0 -5

-       nolock = !spin_trylock_irqsave(&spinlock, flags);
-       superio_enter();
        superio_select(GPIO);
        superio_outb(0x00, WDTCTRL);
        superio_outb(0x00, WDTCFG);

@@ -752,8 +765,6 @@ static void __exit it87_wdt_exit(void)
                superio_outb(ciract, ACTREG);
        }
        superio_exit();
-       if (!nolock)
-               spin_unlock_irqrestore(&spinlock, flags);
 
        misc_deregister(&wdt_miscdev);
        unregister_reboot_notifier(&wdt_notifier);
--

1.7.3.1

Quoted 14 lines

 /**

drivers/watchdog/it87_wdt.c +0 -2

@@ -303,8 +308,6 @@ static void wdt_stop(void)
 
  static int wdt_set_timeout(int t)
  {
-       unsigned long flags;
-
         if (t < 1 || t > max_units * 60)
                 return -EINVAL;
 

@@ -313,14 +316,14 @@ static int wdt_set_timeout(int t)

        else
                timeout = t;

Quoted 6 lines

-       spin_lock_irqsave(&spinlock, flags); if (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
+

I don't think you can do that here. You are moving the lock, meaning test_bit is no longer protected by the lock.

Quoted 96 lines

                superio_select(GPIO);
                wdt_update_timeout();
                superio_exit();
        }
-       spin_unlock_irqrestore(&spinlock, flags);
        return 0;
 }

drivers/watchdog/it87_wdt.c +17 -7

@@ -339,12 +342,10 @@ static int wdt_set_timeout(int t)
 
  static int wdt_get_status(int *status)
  {
-       unsigned long flags;
-
         *status = 0;
         if (testmode) {
-               spin_lock_irqsave(&spinlock, flags);
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
                 superio_select(GPIO);
                 if (superio_inb(WDTCTRL) & WDT_ZERO) {
                         superio_outb(0x00, WDTCTRL);

@@ -353,7 +354,6 @@ static int wdt_get_status(int *status)
                 }
 
                 superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
         }
         if (test_and_clear_bit(WDTS_KEEPALIVE, &wdt_status))
                 *status |= WDIOF_KEEPALIVEPING;

@@ -381,7 +381,12 @@ static int wdt_open(struct inode *inode, struct file *file)
         if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status)) {
                 if (nowayout && !test_and_set_bit(WDTS_LOCKED, &wdt_status))
                         __module_get(THIS_MODULE);
-               wdt_start();
+               if (wdt_start()) {
+                       clear_bit(WDTS_LOCKED, &wdt_status);
+                       clear_bit(WDTS_TIMER_RUN, &wdt_status);
+                       clear_bit(WDTS_DEV_OPEN, &wdt_status);
+                       return -EBUSY;
+               }
         }
         return nonseekable_open(inode, file);
  }

@@ -403,7 +408,15 @@ static int wdt_release(struct inode *inode, struct file *file)
  {
         if (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
                 if (test_and_clear_bit(WDTS_EXPECTED, &wdt_status)) {
-                       wdt_stop();
+                       if (wdt_stop()) {
+                               /*
+                                * Stop failed. Just keep the watchdog alive
+                                * and hope nothing bad happens.
+                                */
+                               set_bit(WDTS_EXPECTED, &wdt_status);
+                               wdt_keepalive();
+                               return -EBUSY;
+                       }
                         clear_bit(WDTS_TIMER_RUN, &wdt_status);
                 } else {
                         wdt_keepalive();

@@ -484,7 +497,8 @@ static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                                     &ident, sizeof(ident)) ? -EFAULT : 0;
 

        case WDIOC_GETSTATUS:
-               wdt_get_status(&status);
+               if (wdt_get_status(&status))
+                       return -EBUSY;
                return put_user(status, uarg.i);

        case WDIOC_GETBOOTSTATUS:

drivers/watchdog/it87_wdt.c +0 -0

@@ -501,13 +515,19 @@ static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                 switch (new_options) {

                case WDIOS_DISABLECARD:
                        if (test_bit(WDTS_TIMER_RUN, &wdt_status))
-                               wdt_stop();
+                               if (wdt_stop())
+                                       return -EBUSY; +
                        clear_bit(WDTS_TIMER_RUN, &wdt_status); return 0;

                case WDIOS_ENABLECARD:
-                       if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status))
-                               wdt_start();
+                       if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status)) {
+                               if (wdt_start()) {
+                                       clear_bit(WDTS_TIMER_RUN, &wdt_status);
+                                       return -EBUSY;
+                               }
+                       }
                        return 0;

                default:

drivers/watchdog/it87_wdt.c static int wdt_notify_sys(struct notifier_block *this, unsigned long code, · line 556

Quoted 6 lines

drivers/watchdog/it87_wdt.c +2 -1

@@ -532,7 +552,8 @@ static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
         void *unused)
  {
         if (code = SYS_DOWN || code = SYS_HALT)
-               wdt_stop();
+               if (wdt_stop())
+                       return -EBUSY;

-EBUSY is not a valid return code here.

Quoted 95 lines

drivers/watchdog/it87_wdt.c +3 -4

         return NOTIFY_DONE;
  }
 

@@ -560,16 +581,15 @@ static int __init it87_wdt_init(void)
         int rc = 0;
         int try_gameport = !nogameport;
         u8  chip_rev;
-       unsigned long flags;
 
         wdt_status = 0;
 
-       spin_lock_irqsave(&spinlock, flags);
-       superio_enter();
+       if (superio_enter())
+               return -EBUSY;
+
         chip_type = superio_inw(CHIPID);
         chip_rev  = superio_inb(CHIPREV) & 0x0f;
         superio_exit();
-       spin_unlock_irqrestore(&spinlock, flags);
 
         switch (chip_type) {

        case IT8702_ID:

drivers/watchdog/it87_wdt.c +2 -3

@@ -603,8 +623,8 @@ static int __init it87_wdt_init(void)
                 return -ENODEV;
         }
 
-       spin_lock_irqsave(&spinlock, flags);
-       superio_enter();
+       if (superio_enter())
+               return -EBUSY;
 
         superio_select(GPIO);
         superio_outb(WDT_TOV1, WDTCFG);

@@ -621,14 +641,12 @@ static int __init it87_wdt_init(void)
                 gpact = superio_inb(ACTREG);
                 superio_outb(0x01, ACTREG);
                 superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
                 if (request_region(base, 1, WATCHDOG_NAME))
                         set_bit(WDTS_USE_GP, &wdt_status);

                else
                        rc = -EIO;
        } else {
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags); }

        /* If we haven't Gameport support, try to get CIR support */

drivers/watchdog/it87_wdt.c +2 -3

@@ -646,8 +664,8 @@ static int __init it87_wdt_init(void)
                         goto err_out;
                 }
                 base = CIR_BASE;
-               spin_lock_irqsave(&spinlock, flags);
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
 
                 superio_select(CIR);
                 superio_outw(base, BASEREG);

@@ -660,7 +678,6 @@ static int __init it87_wdt_init(void)
                 }
 
                 superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
         }
 
         if (timeout < 1 || timeout > max_units * 60) {

@@ -711,21 +728,19 @@ err_out_reboot:

 err_out_region:
        release_region(base, test_bit(WDTS_USE_GP, &wdt_status) ? 1 : 8); if (!test_bit(WDTS_USE_GP, &wdt_status)) {
-               spin_lock_irqsave(&spinlock, flags);
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
                superio_select(CIR);
                superio_outb(ciract, ACTREG);
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
        }
 err_out:
        if (try_gameport) {
-               spin_lock_irqsave(&spinlock, flags);
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY; superio_select(GAMEPORT);
                superio_outb(gpact, ACTREG);
                superio_exit();
-               spin_unlock_irqrestore(&spinlock, flags);
        }

        return rc;

drivers/watchdog/it87_wdt.c err_out: · line 752

Quoted 7 lines

drivers/watchdog/it87_wdt.c +2 -2

@@ -733,11 +748,9 @@ err_out:
 
  static void __exit it87_wdt_exit(void)
  {
-       unsigned long flags;
-       int nolock;
+       if (superio_enter())
+               return;

Assumption is that you unregister the device. So even if superio_select fails, you still have to execute the rest of the code.

Quoted 13 lines

drivers/watchdog/it87_wdt.c +0 -4

-       nolock = !spin_trylock_irqsave(&spinlock, flags);
-       superio_enter();
         superio_select(GPIO);
         superio_outb(0x00, WDTCTRL);
         superio_outb(0x00, WDTCFG);

@@ -752,8 +765,6 @@ static void __exit it87_wdt_exit(void)
                 superio_outb(ciract, ACTREG);
         }
         superio_exit();
-       if (!nolock)
-               spin_unlock_irqrestore(&spinlock, flags);
 

Quoted 5 lines

drivers/watchdog/it87_wdt.c +0 -1

         misc_deregister(&wdt_miscdev);
         unregister_reboot_notifier(&wdt_notifier);
--

1.7.3.1

--
Guenter Roeck
Distinguished Engineer
PDU IP Systems

Guenter,

Quoted 14 lines · Guenter Roeck

Quoted 14 lines

/**

drivers/watchdog/it87_wdt.c +0 -2

@@ -303,8 +308,6 @@ static void wdt_stop(void)
 
 static int wdt_set_timeout(int t)
 {
-       unsigned long flags;
-
        if (t < 1 || t > max_units * 60)
                return -EINVAL;
 

@@ -313,14 +316,14 @@ static int wdt_set_timeout(int t)
        else
                timeout = t;
 

Quoted 9 lines

drivers/watchdog/it87_wdt.c static int wdt_set_timeout(int t) · line 322

Quoted 6 lines

drivers/watchdog/it87_wdt.c +3 -2

-       spin_lock_irqsave(&spinlock, flags);
        if (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
-               superio_enter();
+               if (superio_enter())
+                       return -EBUSY;
+

I don't think you can do that here. You are moving the lock, meaning test_bit is no longer protected by the lock.

I am not sure I am in agreement with your here. If you look at other places in the original driver I see sections of code in "wdt_ioctl" that look as follows:

        case WDIOC_SETOPTIONS:
                if (get_user(new_options, uarg.i))
                        return -EFAULT;

                switch (new_options) {
                case WDIOS_DISABLECARD:
                        if (test_bit(WDTS_TIMER_RUN, &wdt_status))
                                wdt_stop();
                        clear_bit(WDTS_TIMER_RUN, &wdt_status);
                        return 0;

                case WDIOS_ENABLECARD:
                        if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status))
                                wdt_start();
                        return 0;

                default:
                        return -EFAULT;
                }

They have run through manipulating the "WDTS_TIMER_RUN" bit in wdt_status without touching the spinlock. "wdt_stop" does acquire the spinlock before touching the hardware through superio_enter. It seems to me that the original writers of this driver were using the spinlock to isolate access to the hardware and we will be achieving the same by the use of "request_muxed_region" call from superio_enter.