The tty lock is held when the tty driver's open method is called
(from the lone call-site, tty_open()). The call-tree audit [1] of
tty_port_open() is a closed graph of the callers of tty_port_open();
ie., all callers originate from only tty_open().
Of these callers, none drop the tty lock.
Also, document that 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_open()
tty_open()
tty->ops->open() --+
|
rs_open():arch/ia64/hp/sim/simserial.c
*line_open():arch/um/drivers/line.c
gdm_tty_open():drivers/staging/gdm724x/gdm_tty.c
fwtty_open():drivers/staging/fwserial/fwserial.c
acm_tty_open():drivers/usb/class/cdc-acm.c
serial_open():drivers/usb/serial/usb-serial.c
pti_tty_driver_open():drivers/misc/pti.c
ipoctal_open():drivers/ipack/devices/ipoctal.c
isicom_open():drivers/tty/isicom.c
dashtty_open():drivers/tty/metag_da.c
goldfish_tty_open():drivers/tty/goldfish.c
ehv_bc_tty_open():drivers/tty/ehv_bytechan.c
mxser_open():drivers/tty/mxser.c
kgdb_nmi_tty_open():drivers/tty/serial/kgdb_nmi.c
ifx_spi_open():drivers/tty/serial/ifx6x60.c
smd_tty_open():drivers/tty/serial/msm_smd_tty.c
ntty_open():drivers/tty/nozomi.c
capinc_tty_open():drivers/isdn/capi/capi.c
tpk_open():drivers/char/ttyprintk.c
sdio_uart_open():drivers/mmc/card/sdio_uart.c
rfcomm_tty_open():net/bluetooth/rfcomm/tty.c
|
+- tty_port_open()
* line_open() is the .open method for 2 um drivers
declared in ./arch/um/drivers/stdio_console.c and
in ./arch/um/drivers/ssl.c, and not called directly
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
drivers/tty/tty_port.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index bcc15f7..f469869 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -572,6 +572,14 @@ int tty_port_install(struct tty_port *port, struct tty_driver *driver,
}
EXPORT_SYMBOL_GPL(tty_port_install);
+/**
+ * tty_port_open
+ *
+ * Caller holds tty lock.
+ *
+ * NB: may drop and reacquire tty lock (in tty_port_block_til_ready()) so
+ * tty and tty_port may have changed state (eg., may be hung up now)
+ */
int tty_port_open(struct tty_port *port, struct tty_struct *tty,
struct file *filp)
{
--
2.0.0
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