Commit 67abb96c authored by Byungchul Park's avatar Byungchul Park Committed by Paul E. McKenney
Browse files

rcu: Check the range of jiffies_till_{first,next}_fqs when setting them 



Currently, the range of jiffies_till_{first,next}_fqs are checked and
adjusted on and on in the loop of rcu_gp_kthread on runtime.

However, it's enough to check them only when setting them, not every
time in the loop. So make them handled on a setting time via sysfs.

Signed-off-by: default avatarByungchul Park <byungchul.park@lge.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 47199a08

kernel/rcu/tree.c

+32 −13
Original line number Diff line number Diff line
@@ -510,8 +510,38 @@ static ulong jiffies_till_first_fqs = ULONG_MAX; 
static ulong jiffies_till_next_fqs = ULONG_MAX;

static bool rcu_kick_kthreads;



module_param(jiffies_till_first_fqs, ulong, 0644);

module_param(jiffies_till_next_fqs, ulong, 0644);

static int param_set_first_fqs_jiffies(const char *val, const struct kernel_param *kp)

{

	ulong j;

	int ret = kstrtoul(val, 0, &j);



	if (!ret)

		WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : j);

	return ret;

}



static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param *kp)

{

	ulong j;

	int ret = kstrtoul(val, 0, &j);



	if (!ret)

		WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1));

	return ret;

}



static struct kernel_param_ops first_fqs_jiffies_ops = {

	.set = param_set_first_fqs_jiffies,

	.get = param_get_ulong,

};



static struct kernel_param_ops next_fqs_jiffies_ops = {

	.set = param_set_next_fqs_jiffies,

	.get = param_get_ulong,

};



module_param_cb(jiffies_till_first_fqs, &first_fqs_jiffies_ops, &jiffies_till_first_fqs, 0644);

module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next_fqs, 0644);

module_param(rcu_kick_kthreads, bool, 0644);



/*
@@ -2180,10 +2210,6 @@ static int __noreturn rcu_gp_kthread(void *arg) 
		/* Handle quiescent-state forcing. */

		first_gp_fqs = true;

		j = jiffies_till_first_fqs;

		if (j > HZ) {

			j = HZ;

			jiffies_till_first_fqs = HZ;

		}

		ret = 0;

		for (;;) {

			if (!ret) {
@@ -2218,13 +2244,6 @@ static int __noreturn rcu_gp_kthread(void *arg) 
				WRITE_ONCE(rsp->gp_activity, jiffies);

				ret = 0; /* Force full wait till next FQS. */

				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;

				}

			} else {

				/* Deal with stray signal. */

				cond_resched_tasks_rcu_qs();

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