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authorChuck Ebbert <76306.1226@compuserve.com>2005-08-19 14:14:07 +0200
committerWim Van Sebroeck <wim@iguana.be>2005-09-03 13:59:46 +0200
commit1cc77248106aafc12ba529953f652d6f8db2c84d (patch)
tree6e5f8ee1053e7add2ec1890b594dc4086ae39f09 /drivers/char
parent93642ecd463df30d032da8ac37c2676cee4ad876 (diff)
[WATCHDOG] softdog-timer-running-oops.patch
The softdog watchdog timer has a bug that can create an oops: 1. Load the module without the nowayout option. 2. Open the driver and close it without writing 'V' before close. 3. Unload the module. The timer will continue to run... 4. Oops happens when timer fires. Reported Sun, 10 Oct 2004, by Michael Schierl <schierlm@gmx.de> Fix is easy: always take a reference on the module on open. Release it only when the device is closed and no timer is running. Tested on 2.6.13-rc6 using the soft_noboot option. While the timer is running and the device is closed, the module use count stays at 1. After the timer fires, it drops to 0. Repeatedly opening and closing the driver caused no problems. Please apply. Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/watchdog/softdog.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/drivers/char/watchdog/softdog.c b/drivers/char/watchdog/softdog.c
index 4d7ed931f5c..20e5eb8667f 100644
--- a/drivers/char/watchdog/softdog.c
+++ b/drivers/char/watchdog/softdog.c
@@ -77,7 +77,7 @@ static void watchdog_fire(unsigned long);
static struct timer_list watchdog_ticktock =
TIMER_INITIALIZER(watchdog_fire, 0, 0);
-static unsigned long timer_alive;
+static unsigned long driver_open, orphan_timer;
static char expect_close;
@@ -87,6 +87,9 @@ static char expect_close;
static void watchdog_fire(unsigned long data)
{
+ if (test_and_clear_bit(0, &orphan_timer))
+ module_put(THIS_MODULE);
+
if (soft_noboot)
printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
else
@@ -128,9 +131,9 @@ static int softdog_set_heartbeat(int t)
static int softdog_open(struct inode *inode, struct file *file)
{
- if(test_and_set_bit(0, &timer_alive))
+ if (test_and_set_bit(0, &driver_open))
return -EBUSY;
- if (nowayout)
+ if (!test_and_clear_bit(0, &orphan_timer))
__module_get(THIS_MODULE);
/*
* Activate timer
@@ -147,11 +150,13 @@ static int softdog_release(struct inode *inode, struct file *file)
*/
if (expect_close == 42) {
softdog_stop();
+ module_put(THIS_MODULE);
} else {
printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
+ set_bit(0, &orphan_timer);
softdog_keepalive();
}
- clear_bit(0, &timer_alive);
+ clear_bit(0, &driver_open);
expect_close = 0;
return 0;
}