diff options
| -rw-r--r-- | kernel/watchdog.c | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 28c833b42124..3600a01c97a9 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -704,6 +704,71 @@ static int proc_watchdog_update(void) static DEFINE_MUTEX(watchdog_proc_mutex); /* + * common function for watchdog, nmi_watchdog and soft_watchdog parameter + * + * caller | table->data points to | 'which' contains the flag(s) + * -------------------|-----------------------|----------------------------- + * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed + * | | with SOFT_WATCHDOG_ENABLED + * -------------------|-----------------------|----------------------------- + * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED + * -------------------|-----------------------|----------------------------- + * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED + */ +static int proc_watchdog_common(int which, struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + int err, old, new; + int *watchdog_param = (int *)table->data; + + mutex_lock(&watchdog_proc_mutex); + + /* + * If the parameter is being read return the state of the corresponding + * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the + * run state of the lockup detectors. + */ + if (!write) { + *watchdog_param = (watchdog_enabled & which) != 0; + err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + } else { + err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (err) + goto out; + + /* + * There is a race window between fetching the current value + * from 'watchdog_enabled' and storing the new value. During + * this race window, watchdog_nmi_enable() can sneak in and + * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. + * The 'cmpxchg' detects this race and the loop retries. + */ + do { + old = watchdog_enabled; + /* + * If the parameter value is not zero set the + * corresponding bit(s), else clear it(them). + */ + if (*watchdog_param) + new = old | which; + else + new = old & ~which; + } while (cmpxchg(&watchdog_enabled, old, new) != old); + + /* + * Update the run state of the lockup detectors. + * Restore 'watchdog_enabled' on failure. + */ + err = proc_watchdog_update(); + if (err) + watchdog_enabled = old; + } +out: + mutex_unlock(&watchdog_proc_mutex); + return err; +} + +/* * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh */ |