1 files changed, 28 insertions, 0 deletions

diff --git a/kernel/kfifo.c b/kernel/kfifo.c
index 64ab045c3d9d..5d1d907378a2 100644
--- a/kernel/kfifo.c
+++ b/kernel/kfifo.c
@@ -122,6 +122,13 @@ unsigned int __kfifo_put(struct kfifo *fifo,
 
         len = min(len, fifo->size - fifo->in + fifo->out);
 
+        /*
+         * Ensure that we sample the fifo->out index -before- we
+         * start putting bytes into the kfifo.
+         */
+
+        smp_mb();
+
         /* first put the data starting from fifo->in to buffer end */
         l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
         memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
@@ -129,6 +136,13 @@ unsigned int __kfifo_put(struct kfifo *fifo,
         /* then put the rest (if any) at the beginning of the buffer */
         memcpy(fifo->buffer, buffer + l, len - l);
 
+        /*
+         * Ensure that we add the bytes to the kfifo -before-
+         * we update the fifo->in index.
+         */
+
+        smp_wmb();
+
         fifo->in += len;
 
         return len;
@@ -154,6 +168,13 @@ unsigned int __kfifo_get(struct kfifo *fifo,
 
         len = min(len, fifo->in - fifo->out);
 
+        /*
+         * Ensure that we sample the fifo->in index -before- we
+         * start removing bytes from the kfifo.
+         */
+
+        smp_rmb();
+
         /* first get the data from fifo->out until the end of the buffer */
         l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
         memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
@@ -161,6 +182,13 @@ unsigned int __kfifo_get(struct kfifo *fifo,
         /* then get the rest (if any) from the beginning of the buffer */
         memcpy(buffer + l, fifo->buffer, len - l);
 
+        /*
+         * Ensure that we remove the bytes from the kfifo -before-
+         * we update the fifo->out index.
+         */
+
+        smp_mb();
+
         fifo->out += len;
 
         return len;