From: Paul Fulghum Remove TTY_DONT_FLIP tty flag. This flag was introduced in 2.1.X kernels to prevent the N_TTY line discipline functions read_chan() and n_tty_receive_buf() from running at the same time. 2.2.15 introduced tty->read_lock to protect access to the N_TTY read buffer, which is the only state requiring protection between these two functions. The current TTY_DONT_FLIP implementation is broken for SMP, and is not universally honored by drivers that send data directly to the line discipline receive_buf function. Because TTY_DONT_FLIP is not necessary, is broken in implementation, and is not universally honored, it is removed. Signed-off-by: Paul Fulghum Cc: Alan Cox Cc: Theodore Ts'o Signed-off-by: Andrew Morton --- drivers/char/mxser.c | 1 - drivers/char/n_tty.c | 6 +----- drivers/char/pty.c | 2 +- drivers/char/tty_io.c | 15 ++------------- drivers/serial/crisv10.c | 6 ------ drivers/serial/jsm/jsm_tty.c | 7 ------- drivers/usb/serial/ir-usb.c | 3 +-- include/linux/tty.h | 1 - net/bluetooth/rfcomm/tty.c | 8 ++------ 9 files changed, 7 insertions(+), 42 deletions(-) diff -puN drivers/char/mxser.c~remove-tty_dont_flip drivers/char/mxser.c --- a/drivers/char/mxser.c~remove-tty_dont_flip +++ a/drivers/char/mxser.c @@ -996,7 +996,6 @@ static int mxser_open(struct tty_struct info->session = current->signal->session; info->pgrp = process_group(current); - clear_bit(TTY_DONT_FLIP, &tty->flags); /* status = mxser_get_msr(info->base, 0, info->port); diff -puN drivers/char/n_tty.c~remove-tty_dont_flip drivers/char/n_tty.c --- a/drivers/char/n_tty.c~remove-tty_dont_flip +++ a/drivers/char/n_tty.c @@ -1132,7 +1132,7 @@ static inline int input_available_p(stru * buffer, and once to drain the space from the (physical) beginning of * the buffer to head pointer. * - * Called under the tty->atomic_read_lock sem and with TTY_DONT_FLIP set + * Called under the tty->atomic_read_lock sem * */ @@ -1271,7 +1271,6 @@ do_it_again: } add_wait_queue(&tty->read_wait, &wait); - set_bit(TTY_DONT_FLIP, &tty->flags); while (nr) { /* First test for status change. */ if (tty->packet && tty->link->ctrl_status) { @@ -1315,9 +1314,7 @@ do_it_again: break; } n_tty_set_room(tty); - clear_bit(TTY_DONT_FLIP, &tty->flags); timeout = schedule_timeout(timeout); - set_bit(TTY_DONT_FLIP, &tty->flags); continue; } __set_current_state(TASK_RUNNING); @@ -1394,7 +1391,6 @@ do_it_again: if (time) timeout = time; } - clear_bit(TTY_DONT_FLIP, &tty->flags); mutex_unlock(&tty->atomic_read_lock); remove_wait_queue(&tty->read_wait, &wait); diff -puN drivers/char/pty.c~remove-tty_dont_flip drivers/char/pty.c --- a/drivers/char/pty.c~remove-tty_dont_flip +++ a/drivers/char/pty.c @@ -101,7 +101,7 @@ static void pty_unthrottle(struct tty_st * * FIXME: Our pty_write method is called with our ldisc lock held but * not our partners. We can't just take the other one blindly without - * risking deadlocks. There is also the small matter of TTY_DONT_FLIP + * risking deadlocks. */ static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count) { diff -puN drivers/char/tty_io.c~remove-tty_dont_flip drivers/char/tty_io.c --- a/drivers/char/tty_io.c~remove-tty_dont_flip +++ a/drivers/char/tty_io.c @@ -784,11 +784,8 @@ restart: } clear_bit(TTY_LDISC, &tty->flags); - clear_bit(TTY_DONT_FLIP, &tty->flags); - if (o_tty) { + if (o_tty) clear_bit(TTY_LDISC, &o_tty->flags); - clear_bit(TTY_DONT_FLIP, &o_tty->flags); - } spin_unlock_irqrestore(&tty_ldisc_lock, flags); /* @@ -1955,7 +1952,6 @@ static void release_dev(struct file * fi * race with the set_ldisc code path. */ clear_bit(TTY_LDISC, &tty->flags); - clear_bit(TTY_DONT_FLIP, &tty->flags); cancel_delayed_work(&tty->buf.work); /* @@ -2785,13 +2781,6 @@ static void flush_to_ldisc(void *private if (disc == NULL) /* !TTY_LDISC */ return; - if (test_bit(TTY_DONT_FLIP, &tty->flags)) { - /* - * Do it after the next timer tick: - */ - schedule_delayed_work(&tty->buf.work, 1); - goto out; - } spin_lock_irqsave(&tty->buf.lock, flags); while((tbuf = tty->buf.head) != NULL) { while ((count = tbuf->commit - tbuf->read) != 0) { @@ -2810,7 +2799,7 @@ static void flush_to_ldisc(void *private tty_buffer_free(tty, tbuf); } spin_unlock_irqrestore(&tty->buf.lock, flags); -out: + tty_ldisc_deref(disc); } diff -puN drivers/serial/crisv10.c~remove-tty_dont_flip drivers/serial/crisv10.c --- a/drivers/serial/crisv10.c~remove-tty_dont_flip +++ a/drivers/serial/crisv10.c @@ -2573,12 +2573,6 @@ static void flush_to_flip_buffer(struct DFLIP( if (1) { - - if (test_bit(TTY_DONT_FLIP, &tty->flags)) { - DEBUG_LOG(info->line, "*** TTY_DONT_FLIP set flip.count %i ***\n", tty->flip.count); - DEBUG_LOG(info->line, "*** recv_cnt %i\n", info->recv_cnt); - } else { - } DEBUG_LOG(info->line, "*** rxtot %i\n", info->icount.rx); DEBUG_LOG(info->line, "ldisc %lu\n", tty->ldisc.chars_in_buffer(tty)); DEBUG_LOG(info->line, "room %lu\n", tty->ldisc.receive_room(tty)); diff -puN drivers/serial/jsm/jsm_tty.c~remove-tty_dont_flip drivers/serial/jsm/jsm_tty.c --- a/drivers/serial/jsm/jsm_tty.c~remove-tty_dont_flip +++ a/drivers/serial/jsm/jsm_tty.c @@ -589,13 +589,6 @@ void jsm_input(struct jsm_channel *ch) ld = tty_ldisc_ref(tp); /* - * If the DONT_FLIP flag is on, don't flush our buffer, and act - * like the ld doesn't have any space to put the data right now. - */ - if (test_bit(TTY_DONT_FLIP, &tp->flags)) - len = 0; - - /* * If we were unable to get a reference to the ld, * don't flush our buffer, and act like the ld doesn't * have any space to put the data right now. diff -puN drivers/usb/serial/ir-usb.c~remove-tty_dont_flip drivers/usb/serial/ir-usb.c --- a/drivers/usb/serial/ir-usb.c~remove-tty_dont_flip +++ a/drivers/usb/serial/ir-usb.c @@ -453,8 +453,7 @@ static void ir_read_bulk_callback (struc tty = port->tty; /* - * FIXME: must not do this in IRQ context, - * must honour TTY_DONT_FLIP + * FIXME: must not do this in IRQ context */ tty->ldisc.receive_buf( tty, diff -puN include/linux/tty.h~remove-tty_dont_flip include/linux/tty.h --- a/include/linux/tty.h~remove-tty_dont_flip +++ a/include/linux/tty.h @@ -259,7 +259,6 @@ struct tty_struct { #define TTY_DO_WRITE_WAKEUP 5 /* Call write_wakeup after queuing new */ #define TTY_PUSH 6 /* n_tty private */ #define TTY_CLOSING 7 /* ->close() in progress */ -#define TTY_DONT_FLIP 8 /* Defer buffer flip */ #define TTY_LDISC 9 /* Line discipline attached */ #define TTY_HW_COOK_OUT 14 /* Hardware can do output cooking */ #define TTY_HW_COOK_IN 15 /* Hardware can do input cooking */ diff -puN net/bluetooth/rfcomm/tty.c~remove-tty_dont_flip net/bluetooth/rfcomm/tty.c --- a/net/bluetooth/rfcomm/tty.c~remove-tty_dont_flip +++ a/net/bluetooth/rfcomm/tty.c @@ -480,12 +480,8 @@ static void rfcomm_dev_data_ready(struct BT_DBG("dlc %p tty %p len %d", dlc, tty, skb->len); - if (test_bit(TTY_DONT_FLIP, &tty->flags)) { - tty_buffer_request_room(tty, skb->len); - tty_insert_flip_string(tty, skb->data, skb->len); - tty_flip_buffer_push(tty); - } else - tty->ldisc.receive_buf(tty, skb->data, NULL, skb->len); + tty_insert_flip_string(tty, skb->data, skb->len); + tty_flip_buffer_push(tty); kfree_skb(skb); } _