Merge tag 'v4.15-rc1' into next-seccomp

Linux 4.15-rc1

1 files changed, 14 insertions, 0 deletions

diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index a3167941093b..6ef600aa0f47 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 #include <linux/percpu.h>
 #include <linux/sched.h>
 #include <linux/osq_lock.h>
@@ -109,6 +110,19 @@ bool osq_lock(struct optimistic_spin_queue *lock)
 
 	prev = decode_cpu(old);
 	node->prev = prev;
+
+	/*
+	 * osq_lock()			unqueue
+	 *
+	 * node->prev = prev		osq_wait_next()
+	 * WMB				MB
+	 * prev->next = node		next->prev = prev // unqueue-C
+	 *
+	 * Here 'node->prev' and 'next->prev' are the same variable and we need
+	 * to ensure these stores happen in-order to avoid corrupting the list.
+	 */
+	smp_wmb();
+
 	WRITE_ONCE(prev->next, node);
 
 	/*