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n_tty: Protect minimum_to_wake reset for concurrent readers 

With multiple, concurrent readers (each waiting to acquire the
atomic_read_lock mutex), a departing reader may mistakenly reset
minimum_to_wake after a new reader has already set a new value.

Protect the minimum_to_wake reset with the atomic_read_lock critical
section.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Peter Hurley 2013-11-07 14:01:57 -05:00 committed by Greg Kroah-Hartman
parent d4855e1fc0
commit aebf045382
1 changed files with 2 additions and 2 deletions
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4
drivers/tty/n_tty.c
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@ -2249,12 +2249,12 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
n_tty_set_room(tty);
up_read(&tty->termios_rwsem);
mutex_unlock(&ldata->atomic_read_lock);
remove_wait_queue(&tty->read_wait, &wait);
if (!waitqueue_active(&tty->read_wait))
ldata->minimum_to_wake = minimum;
mutex_unlock(&ldata->atomic_read_lock);
__set_current_state(TASK_RUNNING);
if (b - buf)
retval = b - buf;