Commit bafb0bd2 authored by Jiri Slaby's avatar Jiri Slaby Committed by Greg Kroah-Hartman

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: default avatarJiri Slaby <jslaby@suse.cz>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 426929f8
......@@ -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);
......
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