From 9d2ad24306f2fafc3612e5a216aab31f9e56e879 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 24 Jun 2012 10:15:02 -0700 Subject: rcu: Make RCU_FAST_NO_HZ respect nohz= boot parameter If the nohz= boot parameter disables nohz, then RCU_FAST_NO_HZ needs to also disable itself. This commit therefore checks for tick_nohz_enabled being zero, disabling rcu_prepare_for_idle() if so. This commit assumes that tick_nohz_enabled can change at runtime: If this is not the case, then a simpler approach suffices. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- kernel/rcutree_plugin.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'kernel/rcutree_plugin.h') diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index c28d25522a81..3508000e077d 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1971,6 +1971,8 @@ static void rcu_idle_count_callbacks_posted(void) #define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ +extern int tick_nohz_enabled; + /* * Does the specified flavor of RCU have non-lazy callbacks pending on * the specified CPU? Both RCU flavor and CPU are specified by the @@ -2112,6 +2114,7 @@ static void rcu_cleanup_after_idle(int cpu) del_timer(&rdtp->idle_gp_timer); trace_rcu_prep_idle("Cleanup after idle"); + rdtp->tick_nohz_enabled_snap = ACCESS_ONCE(tick_nohz_enabled); } /* @@ -2137,6 +2140,18 @@ static void rcu_prepare_for_idle(int cpu) { struct timer_list *tp; struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); + int tne; + + /* Handle nohz enablement switches conservatively. */ + tne = ACCESS_ONCE(tick_nohz_enabled); + if (tne != rdtp->tick_nohz_enabled_snap) { + if (rcu_cpu_has_callbacks(cpu)) + invoke_rcu_core(); /* force nohz to see update. */ + rdtp->tick_nohz_enabled_snap = tne; + return; + } + if (!tne) + return; /* * If this is an idle re-entry, for example, due to use of -- cgit v1.2.3