watchdog: Add Locking support

This patch fixes some potential multithreading issues, despite only
allowing one process to open the /dev/watchdog device, we can still get
called multiple times at the same time, since a program could be using thread,
or could share the fd after a fork.

This causes 2 potential problems:
1) watchdog_start / open do an unlocked test_n_set / test_n_clear,
   if these 2 race, the watchdog could be stopped while the active
   bit indicates it is running or visa versa.

2) Most watchdog_dev drivers probably assume that only one
   watchdog-op will get called at a time, this is not necessary
   true atm.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
This commit is contained in:
Hans de Goede 2012-05-22 11:40:26 +02:00 committed by Wim Van Sebroeck
parent 7a87982420
commit f4e9c82f64
4 changed files with 29 additions and 0 deletions

View File

@ -50,6 +50,7 @@ struct watchdog_device {
unsigned int min_timeout;
unsigned int max_timeout;
void *driver_data;
struct mutex lock;
unsigned long status;
};
@ -74,6 +75,7 @@ It contains following fields:
* driver_data: a pointer to the drivers private data of a watchdog device.
This data should only be accessed via the watchdog_set_drvdata and
watchdog_get_drvdata routines.
* lock: Mutex for WatchDog Timer Driver Core internal use only.
* status: this field contains a number of status bits that give extra
information about the status of the device (Like: is the watchdog timer
running/active, is the nowayout bit set, is the device opened via

View File

@ -79,6 +79,7 @@ int watchdog_register_device(struct watchdog_device *wdd)
* corrupted in a later stage then we expect a kernel panic!
*/
mutex_init(&wdd->lock);
id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
if (id < 0)
return id;

View File

@ -63,6 +63,8 @@ static int watchdog_ping(struct watchdog_device *wddev)
{
int err = 0;
mutex_lock(&wddev->lock);
if (!watchdog_active(wddev))
goto out_ping;
@ -72,6 +74,7 @@ static int watchdog_ping(struct watchdog_device *wddev)
err = wddev->ops->start(wddev); /* restart watchdog */
out_ping:
mutex_unlock(&wddev->lock);
return err;
}
@ -88,6 +91,8 @@ static int watchdog_start(struct watchdog_device *wddev)
{
int err = 0;
mutex_lock(&wddev->lock);
if (watchdog_active(wddev))
goto out_start;
@ -96,6 +101,7 @@ static int watchdog_start(struct watchdog_device *wddev)
set_bit(WDOG_ACTIVE, &wddev->status);
out_start:
mutex_unlock(&wddev->lock);
return err;
}
@ -113,6 +119,8 @@ static int watchdog_stop(struct watchdog_device *wddev)
{
int err = 0;
mutex_lock(&wddev->lock);
if (!watchdog_active(wddev))
goto out_stop;
@ -127,6 +135,7 @@ static int watchdog_stop(struct watchdog_device *wddev)
clear_bit(WDOG_ACTIVE, &wddev->status);
out_stop:
mutex_unlock(&wddev->lock);
return err;
}
@ -147,8 +156,11 @@ static int watchdog_get_status(struct watchdog_device *wddev,
if (!wddev->ops->status)
return -EOPNOTSUPP;
mutex_lock(&wddev->lock);
*status = wddev->ops->status(wddev);
mutex_unlock(&wddev->lock);
return err;
}
@ -171,8 +183,11 @@ static int watchdog_set_timeout(struct watchdog_device *wddev,
(timeout < wddev->min_timeout || timeout > wddev->max_timeout))
return -EINVAL;
mutex_lock(&wddev->lock);
err = wddev->ops->set_timeout(wddev, timeout);
mutex_unlock(&wddev->lock);
return err;
}
@ -193,8 +208,11 @@ static int watchdog_get_timeleft(struct watchdog_device *wddev,
if (!wddev->ops->get_timeleft)
return -EOPNOTSUPP;
mutex_lock(&wddev->lock);
*timeleft = wddev->ops->get_timeleft(wddev);
mutex_unlock(&wddev->lock);
return err;
}
@ -213,8 +231,11 @@ static int watchdog_ioctl_op(struct watchdog_device *wddev, unsigned int cmd,
if (!wddev->ops->ioctl)
return -ENOIOCTLCMD;
mutex_lock(&wddev->lock);
err = wddev->ops->ioctl(wddev, cmd, arg);
mutex_unlock(&wddev->lock);
return err;
}

View File

@ -104,6 +104,7 @@ struct watchdog_ops {
* @min_timeout:The watchdog devices minimum timeout value.
* @max_timeout:The watchdog devices maximum timeout value.
* @driver-data:Pointer to the drivers private data.
* @lock: Lock for watchdog core internal use only.
* @status: Field that contains the devices internal status bits.
*
* The watchdog_device structure contains all information about a
@ -111,6 +112,9 @@ struct watchdog_ops {
*
* The driver-data field may not be accessed directly. It must be accessed
* via the watchdog_set_drvdata and watchdog_get_drvdata helpers.
*
* The lock field is for watchdog core internal use only and should not be
* touched.
*/
struct watchdog_device {
int id;
@ -124,6 +128,7 @@ struct watchdog_device {
unsigned int min_timeout;
unsigned int max_timeout;
void *driver_data;
struct mutex lock;
unsigned long status;
/* Bit numbers for status flags */
#define WDOG_ACTIVE 0 /* Is the watchdog running/active */