[PATCH tip/core/rcu 14/18] rcu: Update jiffies_to_sched_qs and adjust_jiffies_till_sched_qs() comments

[Paul E. McKenney]

This commit better documents the jiffies_to_sched_qs default-value
strategy used by adjust_jiffies_till_sched_qs()

Reported-by: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxx>
---
 kernel/rcu/tree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 466299c3d2da..e117732bcd5d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -406,7 +406,7 @@ static bool rcu_kick_kthreads;
  */
 static ulong jiffies_till_sched_qs = ULONG_MAX;
 module_param(jiffies_till_sched_qs, ulong, 0444);
-static ulong jiffies_to_sched_qs; /* Adjusted version of above if not default */
+static ulong jiffies_to_sched_qs; /* See adjust_jiffies_till_sched_qs(). */
 module_param(jiffies_to_sched_qs, ulong, 0444); /* Display only! */
 
 /*
@@ -424,6 +424,7 @@ static void adjust_jiffies_till_sched_qs(void)
 		WRITE_ONCE(jiffies_to_sched_qs, jiffies_till_sched_qs);
 		return;
 	}
+	/* Otherwise, set to third fqs scan, but bound below on large system. */
 	j = READ_ONCE(jiffies_till_first_fqs) +
 		      2 * READ_ONCE(jiffies_till_next_fqs);
 	if (j < HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV)
-- 
2.17.1