riscom8: fix SMP brokenness

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.

[akpm@linux-foundation.org: use DEFINE_SPINLOCK]
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 94 insertions, 55 deletions

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 46662959477..eb5687beea9 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 102ece4c4e0..d130b87d8ed 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>
 
@@ -81,6 +82,8 @@
 
 static struct tty_driver *riscom_driver;
 
+static DEFINE_SPINLOCK(riscom_lock);
+
 static struct riscom_board rc_board[RC_NBOARD] =  {
         {
                 .base   = RC_IOBASE1,
@@ -217,13 +220,14 @@ 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       */
@@ -234,7 +238,7 @@ 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. */
@@ -812,9 +816,9 @@ 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);
                 
@@ -825,7 +829,7 @@ 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;
 }
 
@@ -901,6 +905,7 @@ 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
@@ -936,19 +941,26 @@ 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)) {
@@ -1020,8 +1032,9 @@ 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;
         
@@ -1088,7 +1101,9 @@ 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, 
@@ -1107,34 +1122,33 @@ 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;
 }
@@ -1150,7 +1164,7 @@ 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;
@@ -1158,7 +1172,9 @@ 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)
@@ -1173,11 +1189,13 @@ 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)
@@ -1212,9 +1230,11 @@ 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);
 }
@@ -1231,11 +1251,15 @@ 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)
@@ -1256,7 +1280,8 @@ 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)
@@ -1270,7 +1295,9 @@ 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;
 }
 
@@ -1279,7 +1306,8 @@ 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;
@@ -1289,7 +1317,8 @@ 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,
@@ -1298,7 +1327,6 @@ 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;
@@ -1332,9 +1360,11 @@ 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;
 }
@@ -1414,17 +1444,19 @@ 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)
@@ -1438,7 +1470,8 @@ 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))  {
@@ -1447,7 +1480,8 @@ 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)
@@ -1461,11 +1495,13 @@ 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)
@@ -1479,13 +1515,15 @@ 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);
 }
 
 /*
@@ -1537,9 +1575,9 @@ 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)) {
@@ -1627,11 +1665,12 @@ 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