Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit c98c406e authored by David Howells's avatar David Howells
Browse files

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: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarMark Salter <msalter@redhat.com>
parent 541880d9

arch/mn10300/kernel/mn10300-serial.c

+8 −6
Original line number Diff line number Diff line
@@ -487,16 +487,17 @@ static void mn10300_serial_receive_interrupt(struct mn10300_serial_port *port) 


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 @@ static int mn10300_serial_poll_get_char(struct uart_port *_port) 


	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));