diff options
| -rw-r--r-- | drivers/tty/n_tty.c | 106 |
1 files changed, 79 insertions, 27 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 4ddfa60c9222..6f8cf3a52861 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -247,8 +247,6 @@ static void n_tty_write_wakeup(struct tty_struct *tty) static void n_tty_check_throttle(struct tty_struct *tty) { - if (tty->driver->type == TTY_DRIVER_TYPE_PTY) - return; /* * Check the remaining room for the input canonicalization * mode. We don't want to throttle the driver if we're in @@ -1512,23 +1510,6 @@ n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag) n_tty_receive_char_flagged(tty, c, flag); } -/** - * n_tty_receive_buf - data receive - * @tty: terminal device - * @cp: buffer - * @fp: flag buffer - * @count: characters - * - * Called by the terminal driver when a block of characters has - * been received. This function must be called from soft contexts - * not from interrupt context. The driver is responsible for making - * calls one at a time and in order (or using flush_to_ldisc) - * - * n_tty_receive_buf()/producer path: - * claims non-exclusive termios_rwsem - * publishes read_head and canon_head - */ - static void n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp, char *fp, int count) @@ -1684,24 +1665,85 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, } } +/** + * n_tty_receive_buf_common - process input + * @tty: device to receive input + * @cp: input chars + * @fp: flags for each char (if NULL, all chars are TTY_NORMAL) + * @count: number of input chars in @cp + * + * Called by the terminal driver when a block of characters has + * been received. This function must be called from soft contexts + * not from interrupt context. The driver is responsible for making + * calls one at a time and in order (or using flush_to_ldisc) + * + * Returns the # of input chars from @cp which were processed. + * + * In canonical mode, the maximum line length is 4096 chars (including + * the line termination char); lines longer than 4096 chars are + * truncated. After 4095 chars, input data is still processed but + * not stored. Overflow processing ensures the tty can always + * receive more input until at least one line can be read. + * + * In non-canonical mode, the read buffer will only accept 4095 chars; + * this provides the necessary space for a newline char if the input + * mode is switched to canonical. + * + * Note it is possible for the read buffer to _contain_ 4096 chars + * in non-canonical mode: the read buffer could already contain the + * maximum canon line of 4096 chars when the mode is switched to + * non-canonical. + * + * n_tty_receive_buf()/producer path: + * claims non-exclusive termios_rwsem + * publishes commit_head or canon_head + */ static int n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp, char *fp, int count, int flow) { struct n_tty_data *ldata = tty->disc_data; - int room, n, rcvd = 0; + int room, n, rcvd = 0, overflow; down_read(&tty->termios_rwsem); while (1) { - room = receive_room(tty); + /* + * When PARMRK is set, each input char may take up to 3 chars + * in the read buf; reduce the buffer space avail by 3x + * + * If we are doing input canonicalization, and there are no + * pending newlines, let characters through without limit, so + * that erase characters will be handled. Other excess + * characters will be beeped. + * + * paired with store in *_copy_from_read_buf() -- guarantees + * the consumer has loaded the data in read_buf up to the new + * read_tail (so this producer will not overwrite unread data) + */ + size_t tail = ldata->read_tail; + + room = N_TTY_BUF_SIZE - (ldata->read_head - tail); + if (I_PARMRK(tty)) + room = (room + 2) / 3; + room--; + if (room <= 0) { + overflow = ldata->icanon && ldata->canon_head == tail; + if (overflow && room < 0) + ldata->read_head--; + room = overflow; + ldata->no_room = flow && !room; + } else + overflow = 0; + n = min(count, room); - if (!n) { - if (flow && !room) - ldata->no_room = 1; + if (!n) break; - } - __receive_buf(tty, cp, fp, n); + + /* ignore parity errors if handling overflow */ + if (!overflow || !fp || *fp != TTY_PARITY) + __receive_buf(tty, cp, fp, n); + cp += n; if (fp) fp += n; @@ -1710,7 +1752,17 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp, } tty->receive_room = room; - n_tty_check_throttle(tty); + + /* Unthrottle if handling overflow on pty */ + if (tty->driver->type == TTY_DRIVER_TYPE_PTY) { + if (overflow) { + tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE); + tty_unthrottle_safe(tty); + __tty_set_flow_change(tty, 0); + } + } else + n_tty_check_throttle(tty); + up_read(&tty->termios_rwsem); return rcvd; |