[Devel] [PATCH RH7] sysctl: panic only on softlockup_panic-th consequent softlockup

[Pavel Tikhomirov]

https://jira.sw.ru/browse/PSBM-52199

Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 kernel/sysctl.c   |  3 ++-
 kernel/watchdog.c | 36 +++++++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c8f7bc3..40dfc98 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -123,6 +123,7 @@ EXPORT_SYMBOL(ve_allow_module_load);
 #ifdef CONFIG_LOCKUP_DETECTOR
 static int sixty = 60;
 static int neg_one = -1;
+static int int_max = INT_MAX;
 #endif
 
 static int zero;
@@ -910,7 +911,7 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= &zero,
-		.extra2		= &one,
+		.extra2		= &int_max,
 	},
 #ifdef CONFIG_SMP
 	{
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index ba61141..171255b 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -304,6 +304,40 @@ static void watchdog_interrupt_count(void)
 static int watchdog_nmi_enable(unsigned int cpu);
 static void watchdog_nmi_disable(unsigned int cpu);
 
+/*
+ * Delay panic until softlockup_panic softlockups in raw.
+ * Consider softlockups are in raw if they fit in interval
+ * of twice as softlockup_panic * softlockup_thresh.
+ * (Soft lockups most likely will come one just after another
+ * with period of softlockup_thresh, but to cover the accumulating
+ * error give them twice as much the time as teoreticaly needed.)
+ */
+
+static int need_panic_on_softlockup(void)
+{
+	static raw_spinlock_t lock = __RAW_SPIN_LOCK_UNLOCKED(lock);
+	static unsigned long intend;
+	static int count;
+	static int thresh;
+	unsigned long now = get_timestamp();
+	int slp = softlockup_panic;
+
+	if (!slp)
+		return 0;
+
+	raw_spin_lock(&lock);
+	if (!intend || time_after(now, intend)) {
+		intend = now + 2 * slp * get_softlockup_thresh();
+		thresh = slp;
+		count = 0;
+	}
+	if (++count >= thresh)
+		return 1;
+	raw_spin_unlock(&lock);
+
+	return 0;
+}
+
 /* watchdog kicker functions */
 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 {
@@ -390,7 +424,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 		}
 
 		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
-		if (softlockup_panic)
+		if (need_panic_on_softlockup())
 			panic("softlockup: hung tasks");
 		__this_cpu_write(soft_watchdog_warn, true);
 	} else
-- 
2.5.5