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    Subject[PATCH v4 04/32] tty: Refactor wait for ldisc refs out of tty_ldisc_hangup()
    Date
    Refactor tty_ldisc_hangup() to extract standalone function,
    tty_ldisc_hangup_wait_idle(), to wait for ldisc references
    to be released.

    Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
    ---
    drivers/tty/tty_ldisc.c | 54 ++++++++++++++++++++++++++++++++-----------------
    1 file changed, 36 insertions(+), 18 deletions(-)

    diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
    index c641321..c5b848a 100644
    --- a/drivers/tty/tty_ldisc.c
    +++ b/drivers/tty/tty_ldisc.c
    @@ -551,6 +551,41 @@ static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
    }

    /**
    + * tty_ldisc_hangup_wait_idle - wait for the ldisc to become idle
    + * @tty: tty to wait for
    + *
    + * Wait for the line discipline to become idle. The discipline must
    + * have been halted for this to guarantee it remains idle.
    + *
    + * Caller must hold legacy and ->ldisc_mutex.
    + */
    +static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty)
    +{
    + while (tty->ldisc) { /* Not yet closed */
    + if (atomic_read(&tty->ldisc->users) != 1) {
    + char cur_n[TASK_COMM_LEN], tty_n[64];
    + long timeout = 3 * HZ;
    + tty_unlock(tty);
    +
    + while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
    + timeout = MAX_SCHEDULE_TIMEOUT;
    + printk_ratelimited(KERN_WARNING
    + "%s: waiting (%s) for %s took too long, but we keep waiting...\n",
    + __func__, get_task_comm(cur_n, current),
    + tty_name(tty, tty_n));
    + }
    + /* must reacquire both locks and preserve lock order */
    + mutex_unlock(&tty->ldisc_mutex);
    + tty_lock(tty);
    + mutex_lock(&tty->ldisc_mutex);
    + continue;
    + }
    + break;
    + }
    + return !!tty->ldisc;
    +}
    +
    +/**
    * tty_set_ldisc - set line discipline
    * @tty: the terminal to set
    * @ldisc: the line discipline
    @@ -826,7 +861,6 @@ void tty_ldisc_hangup(struct tty_struct *tty)
    cancel_work_sync(&tty->port->buf.work);
    set_bit(TTY_LDISC_HALTED, &tty->flags);
    mutex_unlock(&tty->ldisc_mutex);
    -retry:
    tty_lock(tty);
    mutex_lock(&tty->ldisc_mutex);

    @@ -834,23 +868,7 @@ retry:
    reopen it. We could defer this to the next open but
    it means auditing a lot of other paths so this is
    a FIXME */
    - if (tty->ldisc) { /* Not yet closed */
    - if (atomic_read(&tty->ldisc->users) != 1) {
    - char cur_n[TASK_COMM_LEN], tty_n[64];
    - long timeout = 3 * HZ;
    - tty_unlock(tty);
    -
    - while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
    - timeout = MAX_SCHEDULE_TIMEOUT;
    - printk_ratelimited(KERN_WARNING
    - "%s: waiting (%s) for %s took too long, but we keep waiting...\n",
    - __func__, get_task_comm(cur_n, current),
    - tty_name(tty, tty_n));
    - }
    - mutex_unlock(&tty->ldisc_mutex);
    - goto retry;
    - }
    -
    + if (tty_ldisc_hangup_wait_idle(tty)) {
    if (reset == 0) {

    if (!tty_ldisc_reinit(tty, tty->termios.c_line))
    --
    1.8.1.2


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