diff options
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/n_tty.c | 48 |
1 files changed, 37 insertions, 11 deletions
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index b4f5dccad2a..c0285b95cf9 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -99,6 +99,7 @@ static inline int tty_put_user(struct tty_struct *tty, unsigned char x, static void n_tty_set_room(struct tty_struct *tty) { + /* tty->read_cnt is not read locked ? */ int left = N_TTY_BUF_SIZE - tty->read_cnt - 1; /* @@ -121,6 +122,16 @@ static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty) } } +/** + * put_tty_queue - add character to tty + * @c: character + * @tty: tty device + * + * Add a character to the tty read_buf queue. This is done under the + * read_lock to serialize character addition and also to protect us + * against parallel reads or flushes + */ + static void put_tty_queue(unsigned char c, struct tty_struct *tty) { unsigned long flags; @@ -137,14 +148,11 @@ static void put_tty_queue(unsigned char c, struct tty_struct *tty) * check_unthrottle - allow new receive data * @tty; tty device * - * Check whether to call the driver.unthrottle function. - * We test the TTY_THROTTLED bit first so that it always - * indicates the current state. The decision about whether - * it is worth allowing more input has been taken by the caller. + * Check whether to call the driver unthrottle functions + * * Can sleep, may be called under the atomic_read_lock mutex but * this is not guaranteed. */ - static void check_unthrottle(struct tty_struct *tty) { if (tty->count) @@ -158,6 +166,8 @@ static void check_unthrottle(struct tty_struct *tty) * Reset the read buffer counters, clear the flags, * and make sure the driver is unthrottled. Called * from n_tty_open() and n_tty_flush_buffer(). + * + * Locking: tty_read_lock for read fields. */ static void reset_buffer_flags(struct tty_struct *tty) { @@ -181,7 +191,7 @@ static void reset_buffer_flags(struct tty_struct *tty) * at hangup) or when the N_TTY line discipline internally has to * clean the pending queue (for example some signals). * - * Locking: ctrl_lock + * Locking: ctrl_lock, read_lock. */ static void n_tty_flush_buffer(struct tty_struct *tty) @@ -207,6 +217,8 @@ static void n_tty_flush_buffer(struct tty_struct *tty) * * Report the number of characters buffered to be delivered to user * at this instant in time. + * + * Locking: read_lock */ static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty) @@ -410,6 +422,8 @@ break_out: * * Echo user input back onto the screen. This must be called only when * L_ECHO(tty) is true. Called from the driver receive_buf path. + * + * Relies on BKL for tty column locking */ static void echo_char(unsigned char c, struct tty_struct *tty) @@ -422,6 +436,12 @@ static void echo_char(unsigned char c, struct tty_struct *tty) opost(c, tty); } +/** + * finsh_erasing - complete erase + * @tty: tty doing the erase + * + * Relies on BKL for tty column locking + */ static inline void finish_erasing(struct tty_struct *tty) { if (tty->erasing) { @@ -439,6 +459,8 @@ static inline void finish_erasing(struct tty_struct *tty) * Perform erase and necessary output when an erase character is * present in the stream from the driver layer. Handles the complexities * of UTF-8 multibyte symbols. + * + * Locking: read_lock for tty buffers, BKL for column/erasing state */ static void eraser(unsigned char c, struct tty_struct *tty) @@ -447,6 +469,7 @@ static void eraser(unsigned char c, struct tty_struct *tty) int head, seen_alnums, cnt; unsigned long flags; + /* FIXME: locking needed ? */ if (tty->read_head == tty->canon_head) { /* opost('\a', tty); */ /* what do you think? */ return; @@ -481,6 +504,7 @@ static void eraser(unsigned char c, struct tty_struct *tty) } seen_alnums = 0; + /* FIXME: Locking ?? */ while (tty->read_head != tty->canon_head) { head = tty->read_head; @@ -583,6 +607,8 @@ static void eraser(unsigned char c, struct tty_struct *tty) * may caus terminal flushing to take place according to the termios * settings and character used. Called from the driver receive_buf * path so serialized. + * + * Locking: ctrl_lock, read_lock (both via flush buffer) */ static inline void isig(int sig, struct tty_struct *tty, int flush) @@ -1007,6 +1033,8 @@ int is_ignored(int sig) * and is protected from re-entry by the tty layer. The user is * guaranteed that this function will not be re-entered or in progress * when the ldisc is closed. + * + * Locking: Caller holds tty->termios_mutex */ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old) @@ -1266,10 +1294,7 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file, do_it_again: - if (!tty->read_buf) { - printk(KERN_ERR "n_tty_read_chan: read_buf == NULL?!?\n"); - return -EIO; - } + BUG_ON(!tty->read_buf); c = job_control(tty, file); if (c < 0) @@ -1589,7 +1614,7 @@ static unsigned long inq_canon(struct tty_struct *tty) { int nr, head, tail; - if (!tty->canon_data || !tty->read_buf) + if (!tty->canon_data) return 0; head = tty->canon_head; tail = tty->read_tail; @@ -1613,6 +1638,7 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file, case TIOCOUTQ: return put_user(tty_chars_in_buffer(tty), (int __user *) arg); case TIOCINQ: + /* FIXME: Locking */ retval = tty->read_cnt; if (L_ICANON(tty)) retval = inq_canon(tty); |