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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: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
hifive-unleashed-5.1
Byungchul Park 2018-06-01 11:03:09 +09:00 committed by Paul E. McKenney
parent 47199a0812
commit 67abb96cbf
1 changed files with 32 additions and 13 deletions
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45
kernel/rcu/tree.c
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@ -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();