From 67abb96cbf307e16e3c6d1a0328ece085b5ce94c Mon Sep 17 00:00:00 2001 From: Byungchul Park Date: Fri, 1 Jun 2018 11:03:09 +0900 Subject: [PATCH] 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 Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 45 ++++++++++++++++++++++++++++++++------------- 1 file changed, 32 insertions(+), 13 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 4915525559ac..7498a416f63b 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -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();