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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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      Last update: 2007-10-24 00:41    [W:0.052 / U:0.816 seconds]
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