The following commit has been merged into the core/rcu branch of tip:
Commit-ID: 933ada2c3310aa88807e65c8d498b74a2159a9a2
Gitweb: https://git.kernel.org/tip/933ada2c3310aa88807e65c8d498b74a2159a9a2
Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
AuthorDate: Thu, 06 Aug 2020 19:21:48 -07:00
Committer: Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 24 Aug 2020 18:40:26 -07:00
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 <jannh@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/tree.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 36a860c..88f4fa6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1696,6 +1696,15 @@ 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.
*/
static bool rcu_gp_init(void)
@@ -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;
}
|