7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johan Hovold [ Upstream commit e94cda6551d4716b17353fc458baa9e85ddea9ff ] Check the wakeup condition after adding the task to the waitqueue and updating the task state to avoid missing a racing modem status update or disconnect. Store the old icount on entry and do not update it in the completion handler to avoid missing events or reporting spurious ones (due to modem status changes before TIOCMIWAIT was called). Fixes: e68453ed28c5 ("greybus: uart-gb: now builds, more framework added") Cc: stable@kernel.org # 4.9 Cc: Greg Kroah-Hartman Signed-off-by: Johan Hovold Link: https://patch.msgid.link/20260907095305.130762-1-johan@kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/staging/greybus/uart.c | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c index 172cf900eaf0b..2c47418a11ef8 100644 --- a/drivers/staging/greybus/uart.c +++ b/drivers/staging/greybus/uart.c @@ -53,7 +53,6 @@ struct gb_tty { spinlock_t read_lock; spinlock_t write_lock; struct async_icount iocount; - struct async_icount oldcount; wait_queue_head_t wioctl; struct mutex mutex; u8 ctrlin; /* input control lines */ @@ -643,11 +642,16 @@ static int wait_serial_change(struct gb_tty *gb_tty, unsigned long arg) if (!(arg & (TIOCM_DSR | TIOCM_RI | TIOCM_CD))) return -EINVAL; - do { + spin_lock_irq(&gb_tty->read_lock); + old = gb_tty->iocount; + spin_unlock_irq(&gb_tty->read_lock); + + add_wait_queue(&gb_tty->wioctl, &wait); + for (;;) { + set_current_state(TASK_INTERRUPTIBLE); + spin_lock_irq(&gb_tty->read_lock); - old = gb_tty->oldcount; new = gb_tty->iocount; - gb_tty->oldcount = new; spin_unlock_irq(&gb_tty->read_lock); if ((arg & TIOCM_DSR) && (old.dsr != new.dsr)) @@ -657,18 +661,20 @@ static int wait_serial_change(struct gb_tty *gb_tty, unsigned long arg) if ((arg & TIOCM_RI) && (old.rng != new.rng)) break; - add_wait_queue(&gb_tty->wioctl, &wait); - set_current_state(TASK_INTERRUPTIBLE); - schedule(); - remove_wait_queue(&gb_tty->wioctl, &wait); if (gb_tty->disconnected) { - if (arg & TIOCM_CD) - break; retval = -ENODEV; - } else if (signal_pending(current)) { + break; + } + + schedule(); + + if (signal_pending(current)) { retval = -ERESTARTSYS; + break; } - } while (!retval); + } + __set_current_state(TASK_RUNNING); + remove_wait_queue(&gb_tty->wioctl, &wait); return retval; } -- 2.53.0