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    Subject[PATCH 06/24] TTY: ircomm, revamp locking
    Date
    Use self->spinlock only for ctrl_skb and tx_skb. TTY stuff is now
    protected by tty_port->lock. This is needed for further cleanup (and
    conversion to tty_port helpers).

    This also closes the race in the end of close.

    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    Cc: Samuel Ortiz <samuel@sortiz.org>
    Cc: netdev@vger.kernel.org
    ---
    include/net/irda/ircomm_tty.h | 1 -
    net/irda/ircomm/ircomm_tty.c | 38 ++++++++++++++++++--------------------
    2 files changed, 18 insertions(+), 21 deletions(-)

    diff --git a/include/net/irda/ircomm_tty.h b/include/net/irda/ircomm_tty.h
    index e4db3b5..a9027d8 100644
    --- a/include/net/irda/ircomm_tty.h
    +++ b/include/net/irda/ircomm_tty.h
    @@ -96,7 +96,6 @@ struct ircomm_tty_cb {
    struct work_struct tqueue;

    /* Protect concurent access to :
    - * o self->open_count
    * o self->ctrl_skb
    * o self->tx_skb
    * Maybe other things may gain to be protected as well...
    diff --git a/net/irda/ircomm/ircomm_tty.c b/net/irda/ircomm/ircomm_tty.c
    index 8e61026..7b2152c 100644
    --- a/net/irda/ircomm/ircomm_tty.c
    +++ b/net/irda/ircomm/ircomm_tty.c
    @@ -283,13 +283,12 @@ static int ircomm_tty_block_til_ready(struct ircomm_tty_cb *self,
    IRDA_DEBUG(2, "%s(%d):block_til_ready before block on %s open_count=%d\n",
    __FILE__, __LINE__, tty->driver->name, self->port.count);

    - /* As far as I can see, we protect port.count - Jean II */
    - spin_lock_irqsave(&self->spinlock, flags);
    + spin_lock_irqsave(&self->port.lock, flags);
    if (!tty_hung_up_p(filp)) {
    extra_count = 1;
    self->port.count--;
    }
    - spin_unlock_irqrestore(&self->spinlock, flags);
    + spin_unlock_irqrestore(&self->port.lock, flags);
    self->port.blocked_open++;

    while (1) {
    @@ -340,9 +339,9 @@ static int ircomm_tty_block_til_ready(struct ircomm_tty_cb *self,

    if (extra_count) {
    /* ++ is not atomic, so this should be protected - Jean II */
    - spin_lock_irqsave(&self->spinlock, flags);
    + spin_lock_irqsave(&self->port.lock, flags);
    self->port.count++;
    - spin_unlock_irqrestore(&self->spinlock, flags);
    + spin_unlock_irqrestore(&self->port.lock, flags);
    }
    self->port.blocked_open--;

    @@ -409,12 +408,12 @@ static int ircomm_tty_open(struct tty_struct *tty, struct file *filp)
    hashbin_insert(ircomm_tty, (irda_queue_t *) self, line, NULL);
    }
    /* ++ is not atomic, so this should be protected - Jean II */
    - spin_lock_irqsave(&self->spinlock, flags);
    + spin_lock_irqsave(&self->port.lock, flags);
    self->port.count++;

    tty->driver_data = self;
    self->tty = tty;
    - spin_unlock_irqrestore(&self->spinlock, flags);
    + spin_unlock_irqrestore(&self->port.lock, flags);

    IRDA_DEBUG(1, "%s(), %s%d, count = %d\n", __func__ , tty->driver->name,
    self->line, self->port.count);
    @@ -495,10 +494,10 @@ static void ircomm_tty_close(struct tty_struct *tty, struct file *filp)
    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == IRCOMM_TTY_MAGIC, return;);

    - spin_lock_irqsave(&self->spinlock, flags);
    + spin_lock_irqsave(&self->port.lock, flags);

    if (tty_hung_up_p(filp)) {
    - spin_unlock_irqrestore(&self->spinlock, flags);
    + spin_unlock_irqrestore(&self->port.lock, flags);

    IRDA_DEBUG(0, "%s(), returning 1\n", __func__ );
    return;
    @@ -524,20 +523,15 @@ static void ircomm_tty_close(struct tty_struct *tty, struct file *filp)
    self->port.count = 0;
    }
    if (self->port.count) {
    - spin_unlock_irqrestore(&self->spinlock, flags);
    + spin_unlock_irqrestore(&self->port.lock, flags);

    IRDA_DEBUG(0, "%s(), open count > 0\n", __func__ );
    return;
    }

    - /* Hum... Should be test_and_set_bit ??? - Jean II */
    set_bit(ASYNCB_CLOSING, &self->port.flags);

    - /* We need to unlock here (we were unlocking at the end of this
    - * function), because tty_wait_until_sent() may schedule.
    - * I don't know if the rest should be protected somehow,
    - * so someone should check. - Jean II */
    - spin_unlock_irqrestore(&self->spinlock, flags);
    + spin_unlock_irqrestore(&self->port.lock, flags);

    /*
    * Now we wait for the transmit buffer to clear; and we notify
    @@ -552,16 +546,21 @@ static void ircomm_tty_close(struct tty_struct *tty, struct file *filp)
    tty_driver_flush_buffer(tty);
    tty_ldisc_flush(tty);

    + spin_lock_irqsave(&self->port.lock, flags);
    tty->closing = 0;
    self->tty = NULL;

    if (self->port.blocked_open) {
    - if (self->port.close_delay)
    + if (self->port.close_delay) {
    + spin_unlock_irqrestore(&self->port.lock, flags);
    schedule_timeout_interruptible(self->port.close_delay);
    + spin_lock_irqsave(&self->port.lock, flags);
    + }
    wake_up_interruptible(&self->port.open_wait);
    }

    self->port.flags &= ~(ASYNC_NORMAL_ACTIVE|ASYNC_CLOSING);
    + spin_unlock_irqrestore(&self->port.lock, flags);
    wake_up_interruptible(&self->port.close_wait);
    }

    @@ -1003,12 +1002,11 @@ static void ircomm_tty_hangup(struct tty_struct *tty)
    /* ircomm_tty_flush_buffer(tty); */
    ircomm_tty_shutdown(self);

    - /* I guess we need to lock here - Jean II */
    - spin_lock_irqsave(&self->spinlock, flags);
    + spin_lock_irqsave(&self->port.lock, flags);
    self->port.flags &= ~ASYNC_NORMAL_ACTIVE;
    self->tty = NULL;
    self->port.count = 0;
    - spin_unlock_irqrestore(&self->spinlock, flags);
    + spin_unlock_irqrestore(&self->port.lock, flags);

    wake_up_interruptible(&self->port.open_wait);
    }
    --
    1.7.10.3



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