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Subject[PATCH 4/12] riscom8: fix SMP brokenness
Date
After analyzing the elements that save_flags/cli/sti/restore_flags were
protecting, convert their usages to a global spinlock (the easiest and
most obvious next-step). There were some usages of flags being
intentionally cached, because the code already knew the state of
interrupts. These have been taken into account.

This allows us to remove CONFIG_BROKEN_ON_SMP. Completely untested.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
---
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 6549110..27ab43e 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -276,7 +276,7 @@ config N_HDLC

config RISCOM8
tristate "SDL RISCom/8 card support"
- depends on SERIAL_NONSTANDARD && BROKEN_ON_SMP
+ depends on SERIAL_NONSTANDARD
help
This is a driver for the SDL Communications RISCom/8 multiport card,
which gives you many serial ports. You would need something like
diff --git a/drivers/char/riscom8.c b/drivers/char/riscom8.c
index b37e626..45d109c 100644
--- a/drivers/char/riscom8.c
+++ b/drivers/char/riscom8.c
@@ -47,6 +47,7 @@
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/tty_flip.h>
+#include <linux/spinlock.h>

#include <asm/uaccess.h>

@@ -82,6 +83,8 @@
static struct riscom_board * IRQ_to_board[16];
static struct tty_driver *riscom_driver;

+static spinlock_t riscom_lock = SPIN_LOCK_UNLOCKED;
+
static struct riscom_board rc_board[RC_NBOARD] = {
{
.base = RC_IOBASE1,
@@ -218,13 +221,14 @@ static void __init rc_init_CD180(struct riscom_board const * bp)
{
unsigned long flags;

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
rc_out(bp, RC_CTOUT, 0); /* Clear timeout */
rc_wait_CCR(bp); /* Wait for CCR ready */
rc_out(bp, CD180_CCR, CCR_HARDRESET); /* Reset CD180 chip */
- sti();
+ spin_unlock_irqrestore(&riscom_lock, flags);
msleep(50); /* Delay 0.05 sec */
- cli();
+ spin_lock_irqsave(&riscom_lock, flags);
rc_out(bp, CD180_GIVR, RC_ID); /* Set ID for this chip */
rc_out(bp, CD180_GICR, 0); /* Clear all bits */
rc_out(bp, CD180_PILR1, RC_ACK_MINT); /* Prio for modem intr */
@@ -235,7 +239,7 @@ static void __init rc_init_CD180(struct riscom_board const * bp)
rc_out(bp, CD180_PPRH, (RC_OSCFREQ/(1000000/RISCOM_TPS)) >> 8);
rc_out(bp, CD180_PPRL, (RC_OSCFREQ/(1000000/RISCOM_TPS)) & 0xff);

- restore_flags(flags);
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

/* Main probing routine, also sets irq. */
@@ -817,9 +821,9 @@ static int rc_setup_port(struct riscom_board *bp, struct riscom_port *port)
}
port->xmit_buf = (unsigned char *) tmp;
}
-
- save_flags(flags); cli();
-
+
+ spin_lock_irqsave(&riscom_lock, flags);
+
if (port->tty)
clear_bit(TTY_IO_ERROR, &port->tty->flags);

@@ -830,7 +834,7 @@ static int rc_setup_port(struct riscom_board *bp, struct riscom_port *port)
rc_change_speed(bp, port);
port->flags |= ASYNC_INITIALIZED;

- restore_flags(flags);
+ spin_unlock_irqrestore(&riscom_lock, flags);
return 0;
}

@@ -906,6 +910,7 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
int retval;
int do_clocal = 0;
int CD;
+ unsigned long flags;

/*
* If the device is in the middle of being closed, then block
@@ -941,19 +946,26 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
*/
retval = 0;
add_wait_queue(&port->open_wait, &wait);
- cli();
+
+ spin_lock_irqsave(&riscom_lock, flags);
+
if (!tty_hung_up_p(filp))
port->count--;
- sti();
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
+
port->blocked_open++;
while (1) {
- cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
rc_out(bp, CD180_CAR, port_No(port));
CD = rc_in(bp, CD180_MSVR) & MSVR_CD;
rc_out(bp, CD180_MSVR, MSVR_RTS);
bp->DTR &= ~(1u << port_No(port));
rc_out(bp, RC_DTR, bp->DTR);
- sti();
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
+
set_current_state(TASK_INTERRUPTIBLE);
if (tty_hung_up_p(filp) ||
!(port->flags & ASYNC_INITIALIZED)) {
@@ -1025,8 +1037,9 @@ static void rc_close(struct tty_struct * tty, struct file * filp)

if (!port || rc_paranoia_check(port, tty->name, "close"))
return;
-
- save_flags(flags); cli();
+
+ spin_lock_irqsave(&riscom_lock, flags);
+
if (tty_hung_up_p(filp))
goto out;

@@ -1093,7 +1106,9 @@ static void rc_close(struct tty_struct * tty, struct file * filp)
}
port->flags &= ~(ASYNC_NORMAL_ACTIVE|ASYNC_CLOSING);
wake_up_interruptible(&port->close_wait);
-out: restore_flags(flags);
+
+out:
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

static int rc_write(struct tty_struct * tty,
@@ -1112,34 +1127,33 @@ static int rc_write(struct tty_struct * tty,
if (!tty || !port->xmit_buf)
return 0;

- save_flags(flags);
while (1) {
- cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
c = min_t(int, count, min(SERIAL_XMIT_SIZE - port->xmit_cnt - 1,
SERIAL_XMIT_SIZE - port->xmit_head));
- if (c <= 0) {
- restore_flags(flags);
- break;
- }
+ if (c <= 0)
+ break; /* lock continues to be held */

memcpy(port->xmit_buf + port->xmit_head, buf, c);
port->xmit_head = (port->xmit_head + c) & (SERIAL_XMIT_SIZE-1);
port->xmit_cnt += c;
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);

buf += c;
count -= c;
total += c;
}

- cli();
if (port->xmit_cnt && !tty->stopped && !tty->hw_stopped &&
!(port->IER & IER_TXRDY)) {
port->IER |= IER_TXRDY;
rc_out(bp, CD180_CAR, port_No(port));
rc_out(bp, CD180_IER, port->IER);
}
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);

return total;
}
@@ -1155,7 +1169,7 @@ static void rc_put_char(struct tty_struct * tty, unsigned char ch)
if (!tty || !port->xmit_buf)
return;

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);

if (port->xmit_cnt >= SERIAL_XMIT_SIZE - 1)
goto out;
@@ -1163,7 +1177,9 @@ static void rc_put_char(struct tty_struct * tty, unsigned char ch)
port->xmit_buf[port->xmit_head++] = ch;
port->xmit_head &= SERIAL_XMIT_SIZE - 1;
port->xmit_cnt++;
-out: restore_flags(flags);
+
+out:
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

static void rc_flush_chars(struct tty_struct * tty)
@@ -1178,11 +1194,13 @@ static void rc_flush_chars(struct tty_struct * tty)
!port->xmit_buf)
return;

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
port->IER |= IER_TXRDY;
rc_out(port_Board(port), CD180_CAR, port_No(port));
rc_out(port_Board(port), CD180_IER, port->IER);
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

static int rc_write_room(struct tty_struct * tty)
@@ -1217,9 +1235,11 @@ static void rc_flush_buffer(struct tty_struct *tty)
if (rc_paranoia_check(port, tty->name, "rc_flush_buffer"))
return;

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
port->xmit_cnt = port->xmit_head = port->xmit_tail = 0;
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);

tty_wakeup(tty);
}
@@ -1236,11 +1256,15 @@ static int rc_tiocmget(struct tty_struct *tty, struct file *file)
return -ENODEV;

bp = port_Board(port);
- save_flags(flags); cli();
+
+ spin_lock_irqsave(&riscom_lock, flags);
+
rc_out(bp, CD180_CAR, port_No(port));
status = rc_in(bp, CD180_MSVR);
result = rc_in(bp, RC_RI) & (1u << port_No(port)) ? 0 : TIOCM_RNG;
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
+
result |= ((status & MSVR_RTS) ? TIOCM_RTS : 0)
| ((status & MSVR_DTR) ? TIOCM_DTR : 0)
| ((status & MSVR_CD) ? TIOCM_CAR : 0)
@@ -1261,7 +1285,8 @@ static int rc_tiocmset(struct tty_struct *tty, struct file *file,

bp = port_Board(port);

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
if (set & TIOCM_RTS)
port->MSVR |= MSVR_RTS;
if (set & TIOCM_DTR)
@@ -1275,7 +1300,9 @@ static int rc_tiocmset(struct tty_struct *tty, struct file *file,
rc_out(bp, CD180_CAR, port_No(port));
rc_out(bp, CD180_MSVR, port->MSVR);
rc_out(bp, RC_DTR, bp->DTR);
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
+
return 0;
}

@@ -1284,7 +1311,8 @@ static inline void rc_send_break(struct riscom_port * port, unsigned long length
struct riscom_board *bp = port_Board(port);
unsigned long flags;

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
port->break_length = RISCOM_TPS / HZ * length;
port->COR2 |= COR2_ETC;
port->IER |= IER_TXRDY;
@@ -1294,7 +1322,8 @@ static inline void rc_send_break(struct riscom_port * port, unsigned long length
rc_wait_CCR(bp);
rc_out(bp, CD180_CCR, CCR_CORCHG2);
rc_wait_CCR(bp);
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

static inline int rc_set_serial_info(struct riscom_port * port,
@@ -1303,7 +1332,6 @@ static inline int rc_set_serial_info(struct riscom_port * port,
struct serial_struct tmp;
struct riscom_board *bp = port_Board(port);
int change_speed;
- unsigned long flags;

if (copy_from_user(&tmp, newinfo, sizeof(tmp)))
return -EFAULT;
@@ -1337,9 +1365,11 @@ static inline int rc_set_serial_info(struct riscom_port * port,
port->closing_wait = tmp.closing_wait;
}
if (change_speed) {
- save_flags(flags); cli();
+ unsigned long flags;
+
+ spin_lock_irqsave(&riscom_lock, flags);
rc_change_speed(bp, port);
- restore_flags(flags);
+ spin_unlock_irqrestore(&riscom_lock, flags);
}
return 0;
}
@@ -1419,17 +1449,19 @@ static void rc_throttle(struct tty_struct * tty)
return;

bp = port_Board(port);
-
- save_flags(flags); cli();
+
+ spin_lock_irqsave(&riscom_lock, flags);
+
port->MSVR &= ~MSVR_RTS;
rc_out(bp, CD180_CAR, port_No(port));
- if (I_IXOFF(tty)) {
+ if (I_IXOFF(tty)) {
rc_wait_CCR(bp);
rc_out(bp, CD180_CCR, CCR_SSCH2);
rc_wait_CCR(bp);
}
rc_out(bp, CD180_MSVR, port->MSVR);
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

static void rc_unthrottle(struct tty_struct * tty)
@@ -1443,7 +1475,8 @@ static void rc_unthrottle(struct tty_struct * tty)

bp = port_Board(port);

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
port->MSVR |= MSVR_RTS;
rc_out(bp, CD180_CAR, port_No(port));
if (I_IXOFF(tty)) {
@@ -1452,7 +1485,8 @@ static void rc_unthrottle(struct tty_struct * tty)
rc_wait_CCR(bp);
}
rc_out(bp, CD180_MSVR, port->MSVR);
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

static void rc_stop(struct tty_struct * tty)
@@ -1466,11 +1500,13 @@ static void rc_stop(struct tty_struct * tty)

bp = port_Board(port);

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
port->IER &= ~IER_TXRDY;
rc_out(bp, CD180_CAR, port_No(port));
rc_out(bp, CD180_IER, port->IER);
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

static void rc_start(struct tty_struct * tty)
@@ -1484,13 +1520,15 @@ static void rc_start(struct tty_struct * tty)

bp = port_Board(port);

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
if (port->xmit_cnt && port->xmit_buf && !(port->IER & IER_TXRDY)) {
port->IER |= IER_TXRDY;
rc_out(bp, CD180_CAR, port_No(port));
rc_out(bp, CD180_IER, port->IER);
}
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

/*
@@ -1542,9 +1580,9 @@ static void rc_set_termios(struct tty_struct * tty, struct ktermios * old_termio
tty->termios->c_iflag == old_termios->c_iflag)
return;

- save_flags(flags); cli();
+ spin_lock_irqsave(&riscom_lock, flags);
rc_change_speed(port_Board(port), port);
- restore_flags(flags);
+ spin_unlock_irqrestore(&riscom_lock, flags);

if ((old_termios->c_cflag & CRTSCTS) &&
!(tty->termios->c_cflag & CRTSCTS)) {
@@ -1633,11 +1671,12 @@ static void rc_release_drivers(void)
{
unsigned long flags;

- save_flags(flags);
- cli();
+ spin_lock_irqsave(&riscom_lock, flags);
+
tty_unregister_driver(riscom_driver);
put_tty_driver(riscom_driver);
- restore_flags(flags);
+
+ spin_unlock_irqrestore(&riscom_lock, flags);
}

#ifndef MODULE
-
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