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authorHans de Goede <hdegoede@redhat.com>2012-05-22 11:40:26 +0200
committerWim Van Sebroeck <wim@iguana.be>2012-05-30 07:55:23 +0200
commitf4e9c82f64b524314a390b13d3ba7d483f09258f (patch)
tree82d688ae7782234dc01c6a340596bac21531aae4
parent7a87982420e5e126bfefeb42232d1fd92052794e (diff)
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>
-rw-r--r--Documentation/watchdog/watchdog-kernel-api.txt2
-rw-r--r--drivers/watchdog/watchdog_core.c1
-rw-r--r--drivers/watchdog/watchdog_dev.c21
-rw-r--r--include/linux/watchdog.h5
4 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
index ce1fa22aa70b..08d34e11bc54 100644
--- a/Documentation/watchdog/watchdog-kernel-api.txt
+++ b/Documentation/watchdog/watchdog-kernel-api.txt
@@ -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
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index 86a57673abf9..6aa46a90ff02 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -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;
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 76d2572fed25..4d295d229a07 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -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;
}
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index c3545c5d918a..da1dc1b52744 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -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 */