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

drivers/tty/serial/serial_core.c

+1 −1
Original line number Diff line number Diff line
@@ -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);