---

yaml
---
r: 323519
b: refs/heads/master
c: d40011f
h: refs/heads/master
i:
  323517: bcdac13
  323515: e64ec80
  323511: 93b834b
  323503: ab30d05
  323487: 6738ccf
  323455: 6846110
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 394f2769aa0dbcf027bae6fb52835e25e05d332e
+refs/heads/master: d40011f601b450396104de42c631981502946cf0

trunk/Documentation/kernel-parameters.txt

@@ -2385,6 +2385,17 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
 			Set timeout for RCU CPU stall warning messages.
 
+	rcutree.jiffies_till_first_fqs= [KNL,BOOT]
+			Set delay from grace-period initialization to
+			first attempt to force quiescent states.
+			Units are jiffies, minimum value is zero,
+			and maximum value is HZ.
+
+	rcutree.jiffies_till_next_fqs= [KNL,BOOT]
+			Set delay between subsequent attempts to force
+			quiescent states.  Units are jiffies, minimum
+			value is one, and maximum value is HZ.
+
 	rcutorture.fqs_duration= [KNL,BOOT]
 			Set duration of force_quiescent_state bursts.
 

trunk/kernel/rcutree.c

@@ -226,6 +226,12 @@ int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
 module_param(rcu_cpu_stall_suppress, int, 0644);
 module_param(rcu_cpu_stall_timeout, int, 0644);
 
+static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS;
+static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
+
+module_param(jiffies_till_first_fqs, ulong, 0644);
+module_param(jiffies_till_next_fqs, ulong, 0644);
+
 static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *));
 static void force_quiescent_state(struct rcu_state *rsp);
 static int rcu_pending(int cpu);
@@ -1177,6 +1183,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
 static int __noreturn rcu_gp_kthread(void *arg)
 {
 	int fqs_state;
+	unsigned long j;
 	int ret;
 	struct rcu_state *rsp = arg;
 	struct rcu_node *rnp = rcu_get_root(rsp);
@@ -1197,14 +1204,18 @@ static int __noreturn rcu_gp_kthread(void *arg)
 
 		/* Handle quiescent-state forcing. */
 		fqs_state = RCU_SAVE_DYNTICK;
+		j = jiffies_till_first_fqs;
+		if (j > HZ) {
+			j = HZ;
+			jiffies_till_first_fqs = HZ;
+		}
 		for (;;) {
-			rsp->jiffies_force_qs = jiffies +
-						RCU_JIFFIES_TILL_FORCE_QS;
+			rsp->jiffies_force_qs = jiffies + j;
 			ret = wait_event_interruptible_timeout(rsp->gp_wq,
 					(rsp->gp_flags & RCU_GP_FLAG_FQS) ||
 					(!ACCESS_ONCE(rnp->qsmask) &&
 					 !rcu_preempt_blocked_readers_cgp(rnp)),
-					RCU_JIFFIES_TILL_FORCE_QS);
+					j);
 			/* If grace period done, leave loop. */
 			if (!ACCESS_ONCE(rnp->qsmask) &&
 			    !rcu_preempt_blocked_readers_cgp(rnp))
@@ -1218,6 +1229,14 @@ static int __noreturn rcu_gp_kthread(void *arg)
 				cond_resched();
 				flush_signals(current);
 			}
+			j = jiffies_till_next_fqs;
+			if (j > HZ) {
+				j = HZ;
+				jiffies_till_next_fqs = HZ;
+			} else if (j < 1) {
+				j = 1;
+				jiffies_till_next_fqs = 1;
+			}
 		}
 
 		/* Handle grace-period end. */