summaryrefslogtreecommitdiffstats
path: root/kernel/watchdog.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/watchdog.c')
-rw-r--r--kernel/watchdog.c65
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
*/