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authorAlan Cox <alan@redhat.com>2008-10-13 05:45:06 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-13 12:51:44 -0400
commit17b820606e7bdd3be31b001265d0177423fea5eb (patch)
treedf962dfca41e133983ee1a68deaad646a311d8b2 /drivers
parent51383f69ec56fe3f425d5255fb43e18c445e061c (diff)
tty: Minor tidyups and document fixes for n_tty
Remove/fix some bogus NULL checks, comment some locking etc Signed-off-by: Alan Cox <alan@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/char/n_tty.c48
1 files changed, 37 insertions, 11 deletions
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index b4f5dccad2a6..c0285b95cf94 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,
99 99
100static void n_tty_set_room(struct tty_struct *tty) 100static void n_tty_set_room(struct tty_struct *tty)
101{ 101{
102 /* tty->read_cnt is not read locked ? */
102 int left = N_TTY_BUF_SIZE - tty->read_cnt - 1; 103 int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
103 104
104 /* 105 /*
@@ -121,6 +122,16 @@ static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
121 } 122 }
122} 123}
123 124
125/**
126 * put_tty_queue - add character to tty
127 * @c: character
128 * @tty: tty device
129 *
130 * Add a character to the tty read_buf queue. This is done under the
131 * read_lock to serialize character addition and also to protect us
132 * against parallel reads or flushes
133 */
134
124static void put_tty_queue(unsigned char c, struct tty_struct *tty) 135static void put_tty_queue(unsigned char c, struct tty_struct *tty)
125{ 136{
126 unsigned long flags; 137 unsigned long flags;
@@ -137,14 +148,11 @@ static void put_tty_queue(unsigned char c, struct tty_struct *tty)
137 * check_unthrottle - allow new receive data 148 * check_unthrottle - allow new receive data
138 * @tty; tty device 149 * @tty; tty device
139 * 150 *
140 * Check whether to call the driver.unthrottle function. 151 * Check whether to call the driver unthrottle functions
141 * We test the TTY_THROTTLED bit first so that it always 152 *
142 * indicates the current state. The decision about whether
143 * it is worth allowing more input has been taken by the caller.
144 * Can sleep, may be called under the atomic_read_lock mutex but 153 * Can sleep, may be called under the atomic_read_lock mutex but
145 * this is not guaranteed. 154 * this is not guaranteed.
146 */ 155 */
147
148static void check_unthrottle(struct tty_struct *tty) 156static void check_unthrottle(struct tty_struct *tty)
149{ 157{
150 if (tty->count) 158 if (tty->count)
@@ -158,6 +166,8 @@ static void check_unthrottle(struct tty_struct *tty)
158 * Reset the read buffer counters, clear the flags, 166 * Reset the read buffer counters, clear the flags,
159 * and make sure the driver is unthrottled. Called 167 * and make sure the driver is unthrottled. Called
160 * from n_tty_open() and n_tty_flush_buffer(). 168 * from n_tty_open() and n_tty_flush_buffer().
169 *
170 * Locking: tty_read_lock for read fields.
161 */ 171 */
162static void reset_buffer_flags(struct tty_struct *tty) 172static void reset_buffer_flags(struct tty_struct *tty)
163{ 173{
@@ -181,7 +191,7 @@ static void reset_buffer_flags(struct tty_struct *tty)
181 * at hangup) or when the N_TTY line discipline internally has to 191 * at hangup) or when the N_TTY line discipline internally has to
182 * clean the pending queue (for example some signals). 192 * clean the pending queue (for example some signals).
183 * 193 *
184 * Locking: ctrl_lock 194 * Locking: ctrl_lock, read_lock.
185 */ 195 */
186 196
187static void n_tty_flush_buffer(struct tty_struct *tty) 197static void n_tty_flush_buffer(struct tty_struct *tty)
@@ -207,6 +217,8 @@ static void n_tty_flush_buffer(struct tty_struct *tty)
207 * 217 *
208 * Report the number of characters buffered to be delivered to user 218 * Report the number of characters buffered to be delivered to user
209 * at this instant in time. 219 * at this instant in time.
220 *
221 * Locking: read_lock
210 */ 222 */
211 223
212static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty) 224static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
@@ -410,6 +422,8 @@ break_out:
410 * 422 *
411 * Echo user input back onto the screen. This must be called only when 423 * Echo user input back onto the screen. This must be called only when
412 * L_ECHO(tty) is true. Called from the driver receive_buf path. 424 * L_ECHO(tty) is true. Called from the driver receive_buf path.
425 *
426 * Relies on BKL for tty column locking
413 */ 427 */
414 428
415static void echo_char(unsigned char c, struct tty_struct *tty) 429static 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 opost(c, tty); 436 opost(c, tty);
423} 437}
424 438
439/**
440 * finsh_erasing - complete erase
441 * @tty: tty doing the erase
442 *
443 * Relies on BKL for tty column locking
444 */
425static inline void finish_erasing(struct tty_struct *tty) 445static inline void finish_erasing(struct tty_struct *tty)
426{ 446{
427 if (tty->erasing) { 447 if (tty->erasing) {
@@ -439,6 +459,8 @@ static inline void finish_erasing(struct tty_struct *tty)
439 * Perform erase and necessary output when an erase character is 459 * Perform erase and necessary output when an erase character is
440 * present in the stream from the driver layer. Handles the complexities 460 * present in the stream from the driver layer. Handles the complexities
441 * of UTF-8 multibyte symbols. 461 * of UTF-8 multibyte symbols.
462 *
463 * Locking: read_lock for tty buffers, BKL for column/erasing state
442 */ 464 */
443 465
444static void eraser(unsigned char c, struct tty_struct *tty) 466static void eraser(unsigned char c, struct tty_struct *tty)
@@ -447,6 +469,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
447 int head, seen_alnums, cnt; 469 int head, seen_alnums, cnt;
448 unsigned long flags; 470 unsigned long flags;
449 471
472 /* FIXME: locking needed ? */
450 if (tty->read_head == tty->canon_head) { 473 if (tty->read_head == tty->canon_head) {
451 /* opost('\a', tty); */ /* what do you think? */ 474 /* opost('\a', tty); */ /* what do you think? */
452 return; 475 return;
@@ -481,6 +504,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
481 } 504 }
482 505
483 seen_alnums = 0; 506 seen_alnums = 0;
507 /* FIXME: Locking ?? */
484 while (tty->read_head != tty->canon_head) { 508 while (tty->read_head != tty->canon_head) {
485 head = tty->read_head; 509 head = tty->read_head;
486 510
@@ -583,6 +607,8 @@ static void eraser(unsigned char c, struct tty_struct *tty)
583 * may caus terminal flushing to take place according to the termios 607 * may caus terminal flushing to take place according to the termios
584 * settings and character used. Called from the driver receive_buf 608 * settings and character used. Called from the driver receive_buf
585 * path so serialized. 609 * path so serialized.
610 *
611 * Locking: ctrl_lock, read_lock (both via flush buffer)
586 */ 612 */
587 613
588static inline void isig(int sig, struct tty_struct *tty, int flush) 614static inline void isig(int sig, struct tty_struct *tty, int flush)
@@ -1007,6 +1033,8 @@ int is_ignored(int sig)
1007 * and is protected from re-entry by the tty layer. The user is 1033 * and is protected from re-entry by the tty layer. The user is
1008 * guaranteed that this function will not be re-entered or in progress 1034 * guaranteed that this function will not be re-entered or in progress
1009 * when the ldisc is closed. 1035 * when the ldisc is closed.
1036 *
1037 * Locking: Caller holds tty->termios_mutex
1010 */ 1038 */
1011 1039
1012static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old) 1040static 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 1294
1267do_it_again: 1295do_it_again:
1268 1296
1269 if (!tty->read_buf) { 1297 BUG_ON(!tty->read_buf);
1270 printk(KERN_ERR "n_tty_read_chan: read_buf == NULL?!?\n");
1271 return -EIO;
1272 }
1273 1298
1274 c = job_control(tty, file); 1299 c = job_control(tty, file);
1275 if (c < 0) 1300 if (c < 0)
@@ -1589,7 +1614,7 @@ static unsigned long inq_canon(struct tty_struct *tty)
1589{ 1614{
1590 int nr, head, tail; 1615 int nr, head, tail;
1591 1616
1592 if (!tty->canon_data || !tty->read_buf) 1617 if (!tty->canon_data)
1593 return 0; 1618 return 0;
1594 head = tty->canon_head; 1619 head = tty->canon_head;
1595 tail = tty->read_tail; 1620 tail = tty->read_tail;
@@ -1613,6 +1638,7 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
1613 case TIOCOUTQ: 1638 case TIOCOUTQ:
1614 return put_user(tty_chars_in_buffer(tty), (int __user *) arg); 1639 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
1615 case TIOCINQ: 1640 case TIOCINQ:
1641 /* FIXME: Locking */
1616 retval = tty->read_cnt; 1642 retval = tty->read_cnt;
1617 if (L_ICANON(tty)) 1643 if (L_ICANON(tty))
1618 retval = inq_canon(tty); 1644 retval = inq_canon(tty);