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SubjectRe: [PATCH v9 1/2] Use "request_muxed_region" in it87 watchdog drivers
On Sat, May 07, 2011 at 01:20:47AM -0400, Nat Gurumoorthy wrote:
> 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 <natg@google.com>

Hi Nat,

it87_wdt_init() and wdt_ioctl() already have a variable named "rc" defined.
"ret" in addition to "rc" is confusing (granted, the use of "rc" to indicate
that requesting region 1 failed in it87_wdt_init() is confusing as well).

In it8712f_wdt_find(), both err and ret are now defined as return variables.
That should not be necessary.

In wdt_ioctl(), you still have one instance where you return -EBUSY and
not the returned error. I suspect it is because you did not want to define ret
at the function level ... but as mentioned above, rc is already defined, so that is
not really an argument; just use rc.

In it87_wdt_init(), the error return path is problematic. There are a couple of added
return statements without performing the expected error return action, which may leave
some superio bits as well as memory regions dangling. See below for details.

> ---
>
> diff --git a/drivers/watchdog/it8712f_wdt.c b/drivers/watchdog/it8712f_wdt.c
> index 6143f52..c8677ac 100644
> --- a/drivers/watchdog/it8712f_wdt.c
> +++ b/drivers/watchdog/it8712f_wdt.c
> @@ -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 +179,13 @@ static int it8712f_wdt_get_status(void)
> return 0;
> }
>
> -static void it8712f_wdt_enable(void)
> +static int it8712f_wdt_enable(void)
> {
> + int ret = superio_enter();
> + if (ret)
> + return ret;
> +
> printk(KERN_DEBUG NAME ": enabling watchdog timer\n");
> - superio_enter();
> superio_select(LDN_GPIO);
>
> superio_outb(wdt_control_reg, WDT_CONTROL);
> @@ -186,13 +195,17 @@ static void it8712f_wdt_enable(void)
> superio_exit();
>
> it8712f_wdt_ping();
> +
> + return 0;
> }
>
> -static void it8712f_wdt_disable(void)
> +static int it8712f_wdt_disable(void)
> {
> - printk(KERN_DEBUG NAME ": disabling watchdog timer\n");
> + int ret = superio_enter();
> + if (ret)
> + return ret;
>
> - superio_enter();
> + printk(KERN_DEBUG NAME ": disabling watchdog timer\n");
> superio_select(LDN_GPIO);
>
> superio_outb(0, WDT_CONFIG);
> @@ -202,6 +215,7 @@ static void it8712f_wdt_disable(void)
> superio_outb(0, WDT_TIMEOUT);
>
> superio_exit();
> + return 0;
> }
>
> static int it8712f_wdt_notify(struct notifier_block *this,
> @@ -252,6 +266,7 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
> WDIOF_MAGICCLOSE,
> };
> int value;
> + int ret;
>
> switch (cmd) {
> case WDIOC_GETSUPPORT:
> @@ -259,7 +274,9 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
> return -EFAULT;
> return 0;
> case WDIOC_GETSTATUS:
> - superio_enter();
> + ret = superio_enter();
> + if (ret)
> + return ret;
> superio_select(LDN_GPIO);
>
> value = it8712f_wdt_get_status();
> @@ -280,7 +297,9 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
> if (value > (max_units * 60))
> return -EINVAL;
> margin = value;
> - superio_enter();
> + ret = superio_enter();
> + if (ret)
> + return ret;
> superio_select(LDN_GPIO);
>
> it8712f_wdt_update_margin();
> @@ -299,10 +318,14 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
>
> static int it8712f_wdt_open(struct inode *inode, struct file *file)
> {
> + int ret;
> /* only allow one at a time */
> if (test_and_set_bit(0, &wdt_open))
> return -EBUSY;
> - it8712f_wdt_enable();
> +
> + ret = it8712f_wdt_enable();
> + if (ret)
> + return ret;
> return nonseekable_open(inode, file);
> }
>
> @@ -313,7 +336,8 @@ 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())
> + printk(KERN_WARNING NAME "Watchdog disable failed\n");
> }
> expect_close = 0;
> clear_bit(0, &wdt_open);
> @@ -340,8 +364,10 @@ static int __init it8712f_wdt_find(unsigned short *address)
> {
> int err = -ENODEV;
> int chip_type;
> + int ret = superio_enter();
> + if (ret)
> + return ret;
>
> - superio_enter();
> chip_type = superio_inw(DEVID);
> if (chip_type != IT8712F_DEVID)
> goto exit;
> @@ -382,8 +408,6 @@ static int __init it8712f_wdt_init(void)
> {
> int err = 0;
>
> - spin_lock_init(&io_lock);
> -
> if (it8712f_wdt_find(&address))
> return -ENODEV;
>
> @@ -392,7 +416,11 @@ static int __init it8712f_wdt_init(void)
> return -EBUSY;
> }
>
> - it8712f_wdt_disable();
> + err = it8712f_wdt_disable();
> + if (err) {
> + printk(KERN_ERR NAME ": unable to disable watchdog timer.\n");
> + goto out;
> + }
>
> err = register_reboot_notifier(&it8712f_wdt_notifier);
> if (err) {
> diff --git a/drivers/watchdog/it87_wdt.c b/drivers/watchdog/it87_wdt.c
> index b1bc72f..4def56d 100644
> --- a/drivers/watchdog/it87_wdt.c
> +++ b/drivers/watchdog/it87_wdt.c
> @@ -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 +263,11 @@ 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();
> + int ret = superio_enter();
> + if (ret)
> + return ret;
>
> superio_select(GPIO);
> if (test_bit(WDTS_USE_GP, &wdt_status))
> @@ -270,15 +277,15 @@ 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();
> + int ret = superio_enter();
> + if (ret)
> + return ret;
>
> superio_select(GPIO);
> superio_outb(0x00, WDTCTRL);
> @@ -288,7 +295,7 @@ static void wdt_stop(void)
> superio_outb(0x00, WDTVALMSB);
>
> superio_exit();
> - spin_unlock_irqrestore(&spinlock, flags);
> + return 0;
> }
>
> /**
> @@ -303,8 +310,6 @@ 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 +318,15 @@ static int wdt_set_timeout(int t)
> else
> timeout = t;
>
> - spin_lock_irqsave(&spinlock, flags);
> if (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
> - superio_enter();
> + int ret = superio_enter();
> + if (ret)
> + return ret;
> +
> superio_select(GPIO);
> wdt_update_timeout();
> superio_exit();
> }
> - spin_unlock_irqrestore(&spinlock, flags);
> return 0;
> }
>
> @@ -339,12 +345,12 @@ 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();
> + int ret = superio_enter();
> + if (ret)
> + return ret;
> +
> superio_select(GPIO);
> if (superio_inb(WDTCTRL) & WDT_ZERO) {
> superio_outb(0x00, WDTCTRL);
> @@ -353,7 +359,6 @@ 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;
> @@ -379,9 +384,17 @@ static int wdt_open(struct inode *inode, struct file *file)
> if (exclusive && test_and_set_bit(WDTS_DEV_OPEN, &wdt_status))
> return -EBUSY;
> if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status)) {
> + int ret;
> if (nowayout && !test_and_set_bit(WDTS_LOCKED, &wdt_status))
> __module_get(THIS_MODULE);
> - wdt_start();
> +
> + ret = wdt_start();
> + if (ret) {
> + clear_bit(WDTS_LOCKED, &wdt_status);
> + clear_bit(WDTS_TIMER_RUN, &wdt_status);
> + clear_bit(WDTS_DEV_OPEN, &wdt_status);
> + return ret;
> + }
> }
> return nonseekable_open(inode, file);
> }
> @@ -403,7 +416,16 @@ 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();
> + int ret = wdt_stop();
> + if (ret) {
> + /*
> + * Stop failed. Just keep the watchdog alive
> + * and hope nothing bad happens.
> + */
> + set_bit(WDTS_EXPECTED, &wdt_status);
> + wdt_keepalive();
> + return ret;
> + }
> clear_bit(WDTS_TIMER_RUN, &wdt_status);
> } else {
> wdt_keepalive();
> @@ -484,7 +506,8 @@ 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:
> @@ -500,14 +523,22 @@ 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 (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
> + int ret = wdt_stop();
> + if (ret)
> + return ret;
> + }
> 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)) {
> + int ret = wdt_start();
> + if (ret) {
> + clear_bit(WDTS_TIMER_RUN, &wdt_status);
> + return ret;
> + }
> + }
> return 0;
>
> default:
> @@ -560,16 +591,17 @@ static int __init it87_wdt_init(void)
> int rc = 0;
> int try_gameport = !nogameport;
> u8 chip_rev;
> - unsigned long flags;
> + int ret;
>
> wdt_status = 0;
>
> - spin_lock_irqsave(&spinlock, flags);
> - superio_enter();
> + ret = superio_enter();
> + if (ret)
> + return ret;
> +
> 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 +635,9 @@ static int __init it87_wdt_init(void)
> return -ENODEV;
> }
>
> - spin_lock_irqsave(&spinlock, flags);
> - superio_enter();
> + ret = superio_enter();
> + if (ret)
> + return ret;
>
> superio_select(GPIO);
> superio_outb(WDT_TOV1, WDTCFG);
> @@ -621,18 +654,17 @@ 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 */
> if (!test_bit(WDTS_USE_GP, &wdt_status)) {
> + int ret;
> if (!request_region(CIR_BASE, 8, WATCHDOG_NAME)) {
> if (rc == -EIO)
> printk(KERN_ERR PFX
> @@ -646,8 +678,9 @@ static int __init it87_wdt_init(void)
> goto err_out;
> }
> base = CIR_BASE;
> - spin_lock_irqsave(&spinlock, flags);
> - superio_enter();
> + ret = superio_enter();
> + if (ret)
> + return ret;
>
This leaves the memory region unreleased. Should be goto err_out_region,
and you'll have to set rc.

> superio_select(CIR);
> superio_outw(base, BASEREG);
> @@ -660,7 +693,6 @@ static int __init it87_wdt_init(void)
> }
>
> superio_exit();
> - spin_unlock_irqrestore(&spinlock, flags);
> }
>
> if (timeout < 1 || timeout > max_units * 60) {
> @@ -711,21 +743,23 @@ 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();
> + ret = superio_enter();
> + if (ret)
> + return ret;
> +
> 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();
> + ret = superio_enter();
> + if (ret)
> + return ret;
> +
> superio_select(GAMEPORT);
> superio_outb(gpact, ACTREG);
> superio_exit();
> - spin_unlock_irqrestore(&spinlock, flags);
> }
>
> return rc;
> @@ -733,27 +767,22 @@ err_out:
>
> static void __exit it87_wdt_exit(void)
> {
> - unsigned long flags;
> - int nolock;
> -
> - nolock = !spin_trylock_irqsave(&spinlock, flags);
> - superio_enter();
> - superio_select(GPIO);
> - superio_outb(0x00, WDTCTRL);
> - superio_outb(0x00, WDTCFG);
> - superio_outb(0x00, WDTVALLSB);
> - if (max_units > 255)
> - superio_outb(0x00, WDTVALMSB);
> - if (test_bit(WDTS_USE_GP, &wdt_status)) {
> - superio_select(GAMEPORT);
> - superio_outb(gpact, ACTREG);
> - } else {
> - superio_select(CIR);
> - superio_outb(ciract, ACTREG);
> + if (superio_enter() == 0) {
> + superio_select(GPIO);
> + superio_outb(0x00, WDTCTRL);
> + superio_outb(0x00, WDTCFG);
> + superio_outb(0x00, WDTVALLSB);
> + if (max_units > 255)
> + superio_outb(0x00, WDTVALMSB);
> + if (test_bit(WDTS_USE_GP, &wdt_status)) {
> + superio_select(GAMEPORT);
> + superio_outb(gpact, ACTREG);
> + } else {
> + superio_select(CIR);
> + superio_outb(ciract, ACTREG);
> + }
> + superio_exit();
> }
> - superio_exit();
> - if (!nolock)
> - spin_unlock_irqrestore(&spinlock, flags);
>
> misc_deregister(&wdt_miscdev);
> unregister_reboot_notifier(&wdt_notifier);


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