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authorPeter Hurley <peter@hurleysoftware.com>2014-06-16 09:17:01 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-07-10 16:05:19 -0700
commitc590f6b6cf04513c755b65bbeaf7bd1e88203bb0 (patch)
tree786b7f83df2e7a1ed5462c914d759927427d33cf /drivers/tty/tty_port.c
parentaddd4672bb442b23d16f91c5bae866ba1f9ffd4c (diff)
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 <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_port.c')
-rw-r--r--drivers/tty/tty_port.c5
1 files changed, 5 insertions, 0 deletions
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,