1 files changed, 14 insertions, 3 deletions

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 8ebd9f88a6f6..cf78d1985cd8 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -258,7 +258,11 @@ static int __tty_buffer_request_room(struct tty_port *port, size_t size,
                         n->flags = flags;
                         buf->tail = n;
                         b->commit = b->used;
-                        smp_mb();
+                        /* paired w/ barrier in flush_to_ldisc(); ensures the
+                         * latest commit value can be read before the head is
+                         * advanced to the next buffer
+                         */
+                        smp_wmb();
                         b->next = n;
                 } else if (change)
                         size = 0;
@@ -444,17 +448,24 @@ static void flush_to_ldisc(struct work_struct *work)
 
         while (1) {
                 struct tty_buffer *head = buf->head;
+                struct tty_buffer *next;
                 int count;
 
                 /* Ldisc or user is trying to gain exclusive access */
                 if (atomic_read(&buf->priority))
                         break;
 
+                next = head->next;
+                /* paired w/ barrier in __tty_buffer_request_room();
+                 * ensures commit value read is not stale if the head
+                 * is advancing to the next buffer
+                 */
+                smp_rmb();
                 count = head->commit - head->read;
                 if (!count) {
-                        if (head->next == NULL)
+                        if (next == NULL)
                                 break;
-                        buf->head = head->next;
+                        buf->head = next;
                         tty_buffer_free(port, head);
                         continue;
                 }