From c590f6b6cf04513c755b65bbeaf7bd1e88203bb0 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Mon, 16 Jun 2014 09:17:01 -0400 Subject: [PATCH] tty: Document locking for tty_port_block_til_ready() The tty lock is held when the tty driver's open() method is called (from tty_open()). The call-tree audit [1] of tty_port_block_til_ready() is a closed graph of the callers of tty_port_block_til_ready(); ie., all callers originate only from tty_open(). Of these callers, none drop the tty lock. Also, document tty_port_block_til_ready() may drop and reacquire the tty lock when blocking, which means the tty or tty_port may have changed state. [1] Call-tree audit of tty_port_block_til_ready() * does not include call tree of tty_port_open() which is already documented in 'tty: Document locking from tty_port_open()' tty_open() tty->ops->open() --+ | cy_open():drivers/tty/cyclades.c rp_open():drivers/tty/rocket.c rs_open():drivers/tty/amiserial.c moxa_open():drivers/tty/moxa.c gsmtty_open():drivers/tty/n_gsm.c rs_open():drivers/tty/serial/68328serial.c uart_open():drivers/tty/serial/serial_core.c isdn_tty_open():drivers/isdn/i4l/isdn_tty.c mgslpc_open():drivers/char/pcmcia/synclink_cs.c | +- tty_port_block_til_ready() Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_port.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c index f4698696abae..69e072b59127 100644 --- a/drivers/tty/tty_port.c +++ b/drivers/tty/tty_port.c @@ -348,6 +348,11 @@ EXPORT_SYMBOL(tty_port_lower_dtr_rts); * do carrier detect and the dtr_rts method if it supports software * management of these lines. Note that the dtr/rts raise is done each * iteration as a hangup may have previously dropped them while we wait. + * + * Caller holds tty lock. + * + * NB: May drop and reacquire tty lock when blocking, so tty and tty_port + * may have changed state (eg., may have been hung up). */ int tty_port_block_til_ready(struct tty_port *port, -- 2.39.5