Hi Greg, This series cleans up a messy and poorly documented mechanism required at tty final close to prevent drivers from crashing after h/w shutdown. Without special handling, N_TTY echoing will cause driver i/o requests _after_ h/w shutdown, which typically crashes the driver. Currently, the tty_struct::closing flag triggers this special handling. However, this mechanism is error-prone and subject to driver misuse. This series replaces tty->closing with a ldisc-specific interface, tty_ldisc_closing(), and implements this interface for N_TTY. For tty drivers which use tty_port_close_start(), this change eliminates the last vestige of direct driver<->ldisc interaction. The few tty drivers which open-code the close() method [1] still use tty_ldisc_closing() directly. The tty driver is aware final close for the tty has commenced because the tty->count == 1 in the close() method. On final close, the following is also true: 1. port->count == 1. tty drivers which ref count the port, use the --port->count == 0 as a substitute condition for final close. 2. final close is occurring as a result of the last in-use file descriptor release. Consequently, there will be no read/poll/ioctl in-progress. 3. the line discipline instance will be stopped and destroyed immediately after the tty driver completes the close() method 4. the tty itself will be unrefed immediately after the line discipline instance is destroyed. Thus, the ldisc and tty buffers need only be flushed once, as any data received by the tty driver after the flush but before h/w shutdown will be deleted when the line discipline instance is destroyed. No new echoes will occur after the ldisc flush because the echo buffer is also flushed and new input (which otherwise might generate echoes) is ignored while closing. This series removes the extra tty_ldisc_flush() being performed by most drivers after h/w shutdown. Additionally, the ldisc closing state need not be reset since the line discipline instance is being destroyed, so no interface is provided to reset closing. [1] tty drivers which open-code the close() method drivers/staging/dgnc/dgnc_tty.c drivers/staging/dgap/dgap.c drivers/tty/hvc/hvsi.c drivers/tty/serial/68328serial.c drivers/tty/serial/crisv10.c drivers/isdn/i4l/isdn_tty.c drivers/s390/char/con3215.c Changes to v2: * Fixed tty_ldisc_closing() ld use found by Johannes Stezenbach <js@xxxxxxxxx> Regards, Peter Hurley (4): tty: rocket: Remove private close_wait n_tty: Ignore all read data when closing tty: Abstract and encapsulate tty->closing behavior tty: Remove drivers' extra tty_ldisc_flush() drivers/char/pcmcia/synclink_cs.c | 3 --- drivers/isdn/i4l/isdn_tty.c | 2 +- drivers/s390/char/con3215.c | 3 +-- drivers/staging/dgap/dgap.c | 4 +--- drivers/staging/dgnc/dgnc_tty.c | 4 +--- drivers/tty/amiserial.c | 2 -- drivers/tty/hvc/hvsi.c | 2 +- drivers/tty/ipwireless/tty.c | 1 - drivers/tty/n_tty.c | 15 +++++++++++---- drivers/tty/rocket.c | 5 ----- drivers/tty/rocket_int.h | 1 - drivers/tty/serial/68328serial.c | 3 +-- drivers/tty/serial/crisv10.c | 3 +-- drivers/tty/serial/serial_core.c | 3 --- drivers/tty/synclink.c | 1 - drivers/tty/synclink_gt.c | 1 - drivers/tty/synclinkmp.c | 1 - drivers/tty/tty_ldisc.c | 20 ++++++++++++++++++++ drivers/tty/tty_port.c | 5 +---- include/linux/tty.h | 2 +- include/linux/tty_ldisc.h | 9 +++++++++ 21 files changed, 49 insertions(+), 41 deletions(-) -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
