MN10300: ttySM: Use memory barriers correctly in circular buffer logic
Use memory barriers correctly in the circular buffer logic used in the driver,
as documented in Documentation/circular-buffers.txt.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Mark Salter <msalter@redhat.com>
diff --git a/arch/mn10300/kernel/mn10300-serial.c b/arch/mn10300/kernel/mn10300-serial.c
index 339cef4..131b81f 100644
--- a/arch/mn10300/kernel/mn10300-serial.c
+++ b/arch/mn10300/kernel/mn10300-serial.c
@@ -487,16 +487,17 @@
try_again:
/* pull chars out of the hat */
- ix = port->rx_outp;
- if (ix == port->rx_inp) {
+ ix = ACCESS_ONCE(port->rx_outp);
+ if (CIRC_CNT(port->rx_inp, ix, MNSC_BUFFER_SIZE) == 0) {
if (push && !tty->low_latency)
tty_flip_buffer_push(tty);
return;
}
+ smp_read_barrier_depends();
ch = port->rx_buffer[ix++];
st = port->rx_buffer[ix++];
- smp_rmb();
+ smp_mb();
port->rx_outp = ix & (MNSC_BUFFER_SIZE - 1);
port->uart.icount.rx++;
@@ -1657,13 +1658,14 @@
do {
/* pull chars out of the hat */
- ix = port->rx_outp;
- if (ix == port->rx_inp)
+ ix = ACCESS_ONCE(port->rx_outp);
+ if (CIRC_CNT(port->rx_inp, ix, MNSC_BUFFER_SIZE) == 0)
return NO_POLL_CHAR;
+ smp_read_barrier_depends();
ch = port->rx_buffer[ix++];
st = port->rx_buffer[ix++];
- smp_rmb();
+ smp_mb();
port->rx_outp = ix & (MNSC_BUFFER_SIZE - 1);
} while (st & (SC01STR_FEF | SC01STR_PEF | SC01STR_OEF));