There are 3 different drivers that touch the it87 hardware registers.
The 3 drivers have been written independently and access the it87 hardware
registers assuming they are the only driver accessing it. This change
attempts to 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.
01 - Changes to it87 watchdog driver to use "request_muxed_region"
drivers/watchdog/it8712f_wdt.c
drivers/watchdog/it87_wdt.c
02 - Chages to hwmon it87 driver to use "request_muxed_region"
drivers/hwmon/it87.c
drivers/hwmon/it87.c | 14 ++++-
drivers/watchdog/it8712f_wdt.c | 53 ++++++++++++------
drivers/watchdog/it87_wdt.c | 119 ++++++++++++++++++++++------------------
3 files changed, 113 insertions(+), 73 deletions(-)
Signed-off-by: Nat Gurumoorthy <[email protected]>
Patch History:
v7:
- superio_enter return error if call to "request_muxed_region" fails. Rest
of the changes deal with error returns from superio_enter. Changes to
it87_wdt.c are untested.
v6:
- Pay attention to value returned by request_muxed_region. The first call to
request_muxed_region will attempt 10 times to reserve the region before it
gives up. This will typically get called from the driver init routines. If this
succeeds then subsequent calls wait forever for the resource to be available.
v5:
- Remove unnecessary while from superio_enter.
v4:
- Remove extra braces in superio_enter routines.
v3:
- Totally abandon the spinlock based approach and use "request_muxed_region" to
hold off requestors if the resource is busy.
v2:
- More verbose patch headers. Add In-Reply-To: field.
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]>
---
diff --git a/drivers/watchdog/it8712f_wdt.c b/drivers/watchdog/it8712f_wdt.c
index 6143f52..0442889 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 +179,12 @@ 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;
}
-static void it8712f_wdt_disable(void)
+static int it8712f_wdt_disable(void)
{
printk(KERN_DEBUG NAME ": disabling watchdog timer\n");
- superio_enter();
+ if (superio_enter())
+ return -EBUSY;
+
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,
@@ -209,7 +222,8 @@ static int it8712f_wdt_notify(struct notifier_block *this,
{
if (code == SYS_HALT || code == SYS_POWER_OFF)
if (!nowayout)
- it8712f_wdt_disable();
+ if (it8712f_wdt_disable())
+ return -EBUSY;
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) {
diff --git a/drivers/watchdog/it87_wdt.c b/drivers/watchdog/it87_wdt.c
index b1bc72f..39c98cb 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 +263,10 @@ 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;
@@ -313,14 +316,14 @@ 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();
+ if (superio_enter())
+ return -EBUSY;
+
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:
@@ -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;
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;
@@ -733,11 +748,9 @@ err_out:
static void __exit it87_wdt_exit(void)
{
- unsigned long flags;
- int nolock;
+ if (superio_enter())
+ return;
- 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
02 - Chages to hwmon it87 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. "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]>
---
diff --git a/drivers/hwmon/it87.c b/drivers/hwmon/it87.c
index 316b648..fa3ff02 100644
--- a/drivers/hwmon/it87.c
+++ b/drivers/hwmon/it87.c
@@ -108,13 +108,20 @@ superio_select(int ldn)
outb(ldn, VAL);
}
-static inline void
+static inline int
superio_enter(void)
{
+ /*
+ * Try to reserve REG and REG + 1 for exclusive access.
+ */
+ if (!request_muxed_region(REG, 2, DRVNAME))
+ return -EBUSY;
+
outb(0x87, REG);
outb(0x01, REG);
outb(0x55, REG);
outb(0x55, REG);
+ return 0;
}
static inline void
@@ -122,6 +129,7 @@ superio_exit(void)
{
outb(0x02, REG);
outb(0x02, VAL);
+ release_region(REG, 2);
}
/* Logical device 4 registers */
@@ -1546,7 +1554,9 @@ static int __init it87_find(unsigned short *address,
u16 chip_type;
const char *board_vendor, *board_name;
- superio_enter();
+ if (superio_enter())
+ return -EBUSY;
+
chip_type = force_id ? force_id : superio_inw(DEVID);
switch (chip_type) {
--
1.7.3.1
On Mon, Apr 18, 2011 at 03:00:04PM -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 <[email protected]>
> ---
>
> diff --git a/drivers/watchdog/it8712f_wdt.c b/drivers/watchdog/it8712f_wdt.c
> index 6143f52..0442889 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 +179,12 @@ 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;
> }
>
> -static void it8712f_wdt_disable(void)
> +static int it8712f_wdt_disable(void)
> {
> printk(KERN_DEBUG NAME ": disabling watchdog timer\n");
>
> - superio_enter();
> + if (superio_enter())
> + return -EBUSY;
If you lookk at other drivers implementing the same, you'll notice
that the idea is to return the error code you get from superio_enter(),
instead of replacing it with another one. Sure, it is in practice the same,
but that is not the point.
> +
> 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,
> @@ -209,7 +222,8 @@ static int it8712f_wdt_notify(struct notifier_block *this,
> {
> if (code == SYS_HALT || code == SYS_POWER_OFF)
> if (!nowayout)
> - it8712f_wdt_disable();
> + if (it8712f_wdt_disable())
> + return -EBUSY;
That is not a valid return code for notifier calls. Sometimes one has
to ignore an error code. Again, compare with other drivers what they do
in this situation.
>
> 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) {
> diff --git a/drivers/watchdog/it87_wdt.c b/drivers/watchdog/it87_wdt.c
> index b1bc72f..39c98cb 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 +263,10 @@ 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;
>
> @@ -313,14 +316,14 @@ 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();
> + 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.
> 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:
> @@ -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.
> 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;
> @@ -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.
>
> - 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
>
--
Guenter Roeck
Distinguished Engineer
PDU IP Systems
Guenter,
On Thu, Apr 21, 2011 at 9:44 PM, Guenter Roeck
<[email protected]> wrote:
> > ?/**
> > @@ -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;
> >
> > - ? ? ? 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.
I am fixing the rest of the issues pointed out by you and am hoping to
ship out a patch by the end of the week.
Regards
Nat
> > ? ? ? ? ? ? ? ? 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:
> > @@ -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.
>
> > ? ? ? ? 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;
> > @@ -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.
>
> >
> > - ? ? ? 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
> >
>
> --
> Guenter Roeck
> Distinguished Engineer
> PDU IP Systems
--
Regards
Nat Gurumoorthy AB6SJ
On Wed, Apr 27, 2011 at 01:49:01PM -0400, Natarajan Gurumoorthy wrote:
> Guenter,
>
> On Thu, Apr 21, 2011 at 9:44 PM, Guenter Roeck
> <[email protected]> wrote:
> > > /**
> > > @@ -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;
> > >
> > > - 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.
>
Agreed. Thanks for the clarification.
Guenter
All looks good to me.
Parport can also be made to behave politely and I'll post a patch for
that.
Acked-by: Alan Cox <[email protected]>