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Subject[PATCH v3 04/23] 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 904bf75..70d2b86 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -551,6 +551,41 @@ static int tty_ldisc_halt(struct tty_struct *tty)
}

/**
+ * 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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