Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 6b5fc3a1 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Add memory barriers for NOCB leader wakeup 



Wait/wakeup operations do not guarantee ordering on their own.  Instead,
either locking or memory barriers are required.  This commit therefore
adds memory barriers to wake_nocb_leader() and nocb_leader_wait().

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: default avatarKrister Johansen <kjlx@templeofstupid.com>
Cc: <stable@vger.kernel.org> # 4.6.x
parent 511324e4

kernel/rcu/tree_plugin.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -1810,6 +1810,7 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force) 
	if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) {

	if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) {

		/* Prior smp_mb__after_atomic() orders against prior enqueue. */

		/* Prior smp_mb__after_atomic() orders against prior enqueue. */

		WRITE_ONCE(rdp_leader->nocb_leader_sleep, false);

		WRITE_ONCE(rdp_leader->nocb_leader_sleep, false);

		smp_mb(); /* ->nocb_leader_sleep before swake_up(). */

		swake_up(&rdp_leader->nocb_wq);

		swake_up(&rdp_leader->nocb_wq);

	}

	}

}

}
@@ -2064,6 +2065,7 @@ static void nocb_leader_wait(struct rcu_data *my_rdp) 
	 * nocb_gp_head, where they await a grace period.

	 * nocb_gp_head, where they await a grace period.

	 */

	 */

	gotcbs = false;

	gotcbs = false;

	smp_mb(); /* wakeup before ->nocb_head reads. */

	for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) {

	for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) {

		rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head);

		rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head);

		if (!rdp->nocb_gp_head)

		if (!rdp->nocb_gp_head)