From: Jiri Slaby Date: Thu, 25 Aug 2011 13:12:05 +0000 (+0200) Subject: TTY: serial, move locking in uart_close X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=bafb0bd24d7e0e0124318625b239a55d58c757a2;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git TTY: serial, move locking in uart_close So now, when we handle CLOSING flag, there is no point to hold port->mutex over the start of uart_close. Yes, there are still several things to reason about: * port->count etc is and always was protected by a spinlock * ->stop_rx is protected by a spinlock. Otherwise it would race with interrupts. * uart_wait_until_sent -- that one is already called without port->mutex from set_termios and tty_set_ldisc. Should anything be protected there, it would be tx_empty. And by a spinlock. 8250 does this internally... This step is needed to fix system stalls. To not create an AB-BA lock dependency (see next patches). Signed-off-by: Jiri Slaby Acked-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 849bd0d06b2c..0464360781fe 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1253,7 +1253,6 @@ static void uart_close(struct tty_struct *tty, struct file *filp) pr_debug("uart_close(%d) called\n", uport->line); - mutex_lock(&port->mutex); spin_lock_irqsave(&port->lock, flags); if (tty_hung_up_p(filp)) { @@ -1312,6 +1311,7 @@ static void uart_close(struct tty_struct *tty, struct file *filp) uart_wait_until_sent(tty, uport->timeout); } + mutex_lock(&port->mutex); uart_shutdown(tty, state); uart_flush_buffer(tty);