Commit 17b82060 authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds

tty: Minor tidyups and document fixes for n_tty

Remove/fix some bogus NULL checks, comment some locking etc
Signed-off-by: default avatarAlan Cox <alan@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 51383f69
...@@ -99,6 +99,7 @@ static inline int tty_put_user(struct tty_struct *tty, unsigned char x, ...@@ -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) 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; 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) ...@@ -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) static void put_tty_queue(unsigned char c, struct tty_struct *tty)
{ {
unsigned long flags; unsigned long flags;
...@@ -137,14 +148,11 @@ static void put_tty_queue(unsigned char c, struct tty_struct *tty) ...@@ -137,14 +148,11 @@ static void put_tty_queue(unsigned char c, struct tty_struct *tty)
* check_unthrottle - allow new receive data * check_unthrottle - allow new receive data
* @tty; tty device * @tty; tty device
* *
* Check whether to call the driver.unthrottle function. * Check whether to call the driver unthrottle functions
* 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.
* Can sleep, may be called under the atomic_read_lock mutex but * Can sleep, may be called under the atomic_read_lock mutex but
* this is not guaranteed. * this is not guaranteed.
*/ */
static void check_unthrottle(struct tty_struct *tty) static void check_unthrottle(struct tty_struct *tty)
{ {
if (tty->count) if (tty->count)
...@@ -158,6 +166,8 @@ static void check_unthrottle(struct tty_struct *tty) ...@@ -158,6 +166,8 @@ static void check_unthrottle(struct tty_struct *tty)
* Reset the read buffer counters, clear the flags, * Reset the read buffer counters, clear the flags,
* and make sure the driver is unthrottled. Called * and make sure the driver is unthrottled. Called
* from n_tty_open() and n_tty_flush_buffer(). * 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) static void reset_buffer_flags(struct tty_struct *tty)
{ {
...@@ -181,7 +191,7 @@ 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 * at hangup) or when the N_TTY line discipline internally has to
* clean the pending queue (for example some signals). * 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) static void n_tty_flush_buffer(struct tty_struct *tty)
...@@ -207,6 +217,8 @@ 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 * Report the number of characters buffered to be delivered to user
* at this instant in time. * at this instant in time.
*
* Locking: read_lock
*/ */
static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty) static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
...@@ -410,6 +422,8 @@ static ssize_t opost_block(struct tty_struct *tty, ...@@ -410,6 +422,8 @@ static ssize_t opost_block(struct tty_struct *tty,
* *
* Echo user input back onto the screen. This must be called only when * 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. * 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) 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) ...@@ -422,6 +436,12 @@ static void echo_char(unsigned char c, struct tty_struct *tty)
opost(c, 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) static inline void finish_erasing(struct tty_struct *tty)
{ {
if (tty->erasing) { if (tty->erasing) {
...@@ -439,6 +459,8 @@ static inline void finish_erasing(struct tty_struct *tty) ...@@ -439,6 +459,8 @@ static inline void finish_erasing(struct tty_struct *tty)
* Perform erase and necessary output when an erase character is * Perform erase and necessary output when an erase character is
* present in the stream from the driver layer. Handles the complexities * present in the stream from the driver layer. Handles the complexities
* of UTF-8 multibyte symbols. * 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) static void eraser(unsigned char c, struct tty_struct *tty)
...@@ -447,6 +469,7 @@ 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; int head, seen_alnums, cnt;
unsigned long flags; unsigned long flags;
/* FIXME: locking needed ? */
if (tty->read_head == tty->canon_head) { if (tty->read_head == tty->canon_head) {
/* opost('\a', tty); */ /* what do you think? */ /* opost('\a', tty); */ /* what do you think? */
return; return;
...@@ -481,6 +504,7 @@ static void eraser(unsigned char c, struct tty_struct *tty) ...@@ -481,6 +504,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
} }
seen_alnums = 0; seen_alnums = 0;
/* FIXME: Locking ?? */
while (tty->read_head != tty->canon_head) { while (tty->read_head != tty->canon_head) {
head = tty->read_head; head = tty->read_head;
...@@ -583,6 +607,8 @@ static void eraser(unsigned char c, struct tty_struct *tty) ...@@ -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 * may caus terminal flushing to take place according to the termios
* settings and character used. Called from the driver receive_buf * settings and character used. Called from the driver receive_buf
* path so serialized. * path so serialized.
*
* Locking: ctrl_lock, read_lock (both via flush buffer)
*/ */
static inline void isig(int sig, struct tty_struct *tty, int flush) static inline void isig(int sig, struct tty_struct *tty, int flush)
...@@ -1007,6 +1033,8 @@ int is_ignored(int sig) ...@@ -1007,6 +1033,8 @@ int is_ignored(int sig)
* and is protected from re-entry by the tty layer. The user is * 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 * guaranteed that this function will not be re-entered or in progress
* when the ldisc is closed. * when the ldisc is closed.
*
* Locking: Caller holds tty->termios_mutex
*/ */
static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old) 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, ...@@ -1266,10 +1294,7 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file,
do_it_again: do_it_again:
if (!tty->read_buf) { BUG_ON(!tty->read_buf);
printk(KERN_ERR "n_tty_read_chan: read_buf == NULL?!?\n");
return -EIO;
}
c = job_control(tty, file); c = job_control(tty, file);
if (c < 0) if (c < 0)
...@@ -1589,7 +1614,7 @@ static unsigned long inq_canon(struct tty_struct *tty) ...@@ -1589,7 +1614,7 @@ static unsigned long inq_canon(struct tty_struct *tty)
{ {
int nr, head, tail; int nr, head, tail;
if (!tty->canon_data || !tty->read_buf) if (!tty->canon_data)
return 0; return 0;
head = tty->canon_head; head = tty->canon_head;
tail = tty->read_tail; tail = tty->read_tail;
...@@ -1613,6 +1638,7 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file, ...@@ -1613,6 +1638,7 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
case TIOCOUTQ: case TIOCOUTQ:
return put_user(tty_chars_in_buffer(tty), (int __user *) arg); return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
case TIOCINQ: case TIOCINQ:
/* FIXME: Locking */
retval = tty->read_cnt; retval = tty->read_cnt;
if (L_ICANON(tty)) if (L_ICANON(tty))
retval = inq_canon(tty); retval = inq_canon(tty);
......
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