From 933ada2c3310aa88807e65c8d498b74a2159a9a2 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 6 Aug 2020 19:21:48 -0700 Subject: [PATCH] rcu: IPI all CPUs at GP start for strict GPs Currently, each CPU discovers the beginning of a given grace period on its own time, which is again good for efficiency but bad for fast grace periods. This commit therefore uses on_each_cpu() to IPI each CPU after grace-period initialization in order to inform each CPU of the new grace period in a timely manner, but only in kernels build with CONFIG_RCU_STRICT_GRACE_PERIOD=y. Reported-by Jann Horn Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 36a860c4648b..88f4fa639964 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1695,6 +1695,15 @@ static void rcu_gp_torture_wait(void) } } +/* + * Handler for on_each_cpu() to invoke the target CPU's RCU core + * processing. + */ +static void rcu_strict_gp_boundary(void *unused) +{ + invoke_rcu_core(); +} + /* * Initialize a new grace period. Return false if no grace period required. */ @@ -1823,6 +1832,10 @@ static bool rcu_gp_init(void) WRITE_ONCE(rcu_state.gp_activity, jiffies); } + // If strict, make all CPUs aware of new grace period. + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) + on_each_cpu(rcu_strict_gp_boundary, NULL, 0); + return true; }