From f4e9c82f64b524314a390b13d3ba7d483f09258f Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Tue, 22 May 2012 11:40:26 +0200 Subject: 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 Signed-off-by: Wim Van Sebroeck --- drivers/watchdog/watchdog_core.c | 1 + drivers/watchdog/watchdog_dev.c | 21 +++++++++++++++++++++ 2 files changed, 22 insertions(+) (limited to 'drivers/watchdog') diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c index 86a5767..6aa46a9 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 76d2572..4d295d2 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; } -- cgit v1.1