MN10300: Introduce barriers to replace removed volatiles in gdbstub

Introduce into the MN10300 gdbstub a couple of barrier() calls to replace the
removed volatility of the input/output index variables for the Rx ring buffer.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/mn10300/kernel/gdb-io-ttysm.c b/arch/mn10300/kernel/gdb-io-ttysm.c
index c5451592d403..e94c25e8ca05 100644
--- a/arch/mn10300/kernel/gdb-io-ttysm.c
+++ b/arch/mn10300/kernel/gdb-io-ttysm.c
@@ -196,6 +196,7 @@ int gdbstub_io_rx_char(unsigned char *_ch, int nonblock)
 try_again:
         /* pull chars out of the buffer */
         ix = gdbstub_rx_outp;
+        barrier();
         if (ix == gdbstub_rx_inp) {
                 if (nonblock)
                         return -EAGAIN;
@@ -207,6 +208,7 @@ try_again:
 
         ch = gdbstub_rx_buffer[ix++];
         st = gdbstub_rx_buffer[ix++];
+        barrier();
         gdbstub_rx_outp = ix & (PAGE_SIZE - 1);
 
         st &= SC01STR_RXF | SC01STR_RBF | SC01STR_FEF | SC01STR_PEF |