Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * Tty buffer allocation management
4 : */
5 :
6 : #include <linux/types.h>
7 : #include <linux/errno.h>
8 : #include <linux/minmax.h>
9 : #include <linux/tty.h>
10 : #include <linux/tty_driver.h>
11 : #include <linux/tty_flip.h>
12 : #include <linux/timer.h>
13 : #include <linux/string.h>
14 : #include <linux/slab.h>
15 : #include <linux/sched.h>
16 : #include <linux/wait.h>
17 : #include <linux/bitops.h>
18 : #include <linux/delay.h>
19 : #include <linux/module.h>
20 : #include <linux/ratelimit.h>
21 : #include "tty.h"
22 :
23 : #define MIN_TTYB_SIZE 256
24 : #define TTYB_ALIGN_MASK 0xff
25 :
26 : /*
27 : * Byte threshold to limit memory consumption for flip buffers.
28 : * The actual memory limit is > 2x this amount.
29 : */
30 : #define TTYB_DEFAULT_MEM_LIMIT (640 * 1024UL)
31 :
32 : /*
33 : * We default to dicing tty buffer allocations to this many characters
34 : * in order to avoid multiple page allocations. We know the size of
35 : * tty_buffer itself but it must also be taken into account that the
36 : * buffer is 256 byte aligned. See tty_buffer_find for the allocation
37 : * logic this must match.
38 : */
39 :
40 : #define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~TTYB_ALIGN_MASK)
41 :
42 : /**
43 : * tty_buffer_lock_exclusive - gain exclusive access to buffer
44 : * @port: tty port owning the flip buffer
45 : *
46 : * Guarantees safe use of the &tty_ldisc_ops.receive_buf() method by excluding
47 : * the buffer work and any pending flush from using the flip buffer. Data can
48 : * continue to be added concurrently to the flip buffer from the driver side.
49 : *
50 : * See also tty_buffer_unlock_exclusive().
51 : */
52 0 : void tty_buffer_lock_exclusive(struct tty_port *port)
53 : {
54 0 : struct tty_bufhead *buf = &port->buf;
55 :
56 0 : atomic_inc(&buf->priority);
57 0 : mutex_lock(&buf->lock);
58 0 : }
59 : EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
60 :
61 : /**
62 : * tty_buffer_unlock_exclusive - release exclusive access
63 : * @port: tty port owning the flip buffer
64 : *
65 : * The buffer work is restarted if there is data in the flip buffer.
66 : *
67 : * See also tty_buffer_lock_exclusive().
68 : */
69 0 : void tty_buffer_unlock_exclusive(struct tty_port *port)
70 : {
71 0 : struct tty_bufhead *buf = &port->buf;
72 : int restart;
73 :
74 0 : restart = buf->head->commit != buf->head->read;
75 :
76 0 : atomic_dec(&buf->priority);
77 0 : mutex_unlock(&buf->lock);
78 0 : if (restart)
79 0 : queue_work(system_unbound_wq, &buf->work);
80 0 : }
81 : EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
82 :
83 : /**
84 : * tty_buffer_space_avail - return unused buffer space
85 : * @port: tty port owning the flip buffer
86 : *
87 : * Returns: the # of bytes which can be written by the driver without reaching
88 : * the buffer limit.
89 : *
90 : * Note: this does not guarantee that memory is available to write the returned
91 : * # of bytes (use tty_prepare_flip_string() to pre-allocate if memory
92 : * guarantee is required).
93 : */
94 0 : unsigned int tty_buffer_space_avail(struct tty_port *port)
95 : {
96 0 : int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
97 :
98 0 : return max(space, 0);
99 : }
100 : EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
101 :
102 : static void tty_buffer_reset(struct tty_buffer *p, size_t size)
103 : {
104 16 : p->used = 0;
105 16 : p->size = size;
106 16 : p->next = NULL;
107 16 : p->commit = 0;
108 16 : p->lookahead = 0;
109 16 : p->read = 0;
110 16 : p->flags = true;
111 : }
112 :
113 : /**
114 : * tty_buffer_free_all - free buffers used by a tty
115 : * @port: tty port to free from
116 : *
117 : * Remove all the buffers pending on a tty whether queued with data or in the
118 : * free ring. Must be called when the tty is no longer in use.
119 : */
120 0 : void tty_buffer_free_all(struct tty_port *port)
121 : {
122 0 : struct tty_bufhead *buf = &port->buf;
123 : struct tty_buffer *p, *next;
124 : struct llist_node *llist;
125 0 : unsigned int freed = 0;
126 : int still_used;
127 :
128 0 : while ((p = buf->head) != NULL) {
129 0 : buf->head = p->next;
130 0 : freed += p->size;
131 0 : if (p->size > 0)
132 0 : kfree(p);
133 : }
134 0 : llist = llist_del_all(&buf->free);
135 0 : llist_for_each_entry_safe(p, next, llist, free)
136 0 : kfree(p);
137 :
138 0 : tty_buffer_reset(&buf->sentinel, 0);
139 0 : buf->head = &buf->sentinel;
140 0 : buf->tail = &buf->sentinel;
141 :
142 0 : still_used = atomic_xchg(&buf->mem_used, 0);
143 0 : WARN(still_used != freed, "we still have not freed %d bytes!",
144 : still_used - freed);
145 0 : }
146 :
147 : /**
148 : * tty_buffer_alloc - allocate a tty buffer
149 : * @port: tty port
150 : * @size: desired size (characters)
151 : *
152 : * Allocate a new tty buffer to hold the desired number of characters. We
153 : * round our buffers off in 256 character chunks to get better allocation
154 : * behaviour.
155 : *
156 : * Returns: %NULL if out of memory or the allocation would exceed the per
157 : * device queue.
158 : */
159 0 : static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
160 : {
161 : struct llist_node *free;
162 : struct tty_buffer *p;
163 :
164 : /* Round the buffer size out */
165 0 : size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
166 :
167 0 : if (size <= MIN_TTYB_SIZE) {
168 0 : free = llist_del_first(&port->buf.free);
169 0 : if (free) {
170 : p = llist_entry(free, struct tty_buffer, free);
171 : goto found;
172 : }
173 : }
174 :
175 : /* Should possibly check if this fails for the largest buffer we
176 : * have queued and recycle that ?
177 : */
178 0 : if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
179 : return NULL;
180 0 : p = kmalloc(sizeof(struct tty_buffer) + 2 * size,
181 : GFP_ATOMIC | __GFP_NOWARN);
182 0 : if (p == NULL)
183 : return NULL;
184 :
185 : found:
186 0 : tty_buffer_reset(p, size);
187 0 : atomic_add(size, &port->buf.mem_used);
188 0 : return p;
189 : }
190 :
191 : /**
192 : * tty_buffer_free - free a tty buffer
193 : * @port: tty port owning the buffer
194 : * @b: the buffer to free
195 : *
196 : * Free a tty buffer, or add it to the free list according to our internal
197 : * strategy.
198 : */
199 0 : static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
200 : {
201 0 : struct tty_bufhead *buf = &port->buf;
202 :
203 : /* Dumb strategy for now - should keep some stats */
204 0 : WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
205 :
206 0 : if (b->size > MIN_TTYB_SIZE)
207 0 : kfree(b);
208 0 : else if (b->size > 0)
209 0 : llist_add(&b->free, &buf->free);
210 0 : }
211 :
212 : /**
213 : * tty_buffer_flush - flush full tty buffers
214 : * @tty: tty to flush
215 : * @ld: optional ldisc ptr (must be referenced)
216 : *
217 : * Flush all the buffers containing receive data. If @ld != %NULL, flush the
218 : * ldisc input buffer.
219 : *
220 : * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
221 : */
222 0 : void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
223 : {
224 0 : struct tty_port *port = tty->port;
225 0 : struct tty_bufhead *buf = &port->buf;
226 : struct tty_buffer *next;
227 :
228 0 : atomic_inc(&buf->priority);
229 :
230 0 : mutex_lock(&buf->lock);
231 : /* paired w/ release in __tty_buffer_request_room; ensures there are
232 : * no pending memory accesses to the freed buffer
233 : */
234 0 : while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
235 0 : tty_buffer_free(port, buf->head);
236 0 : buf->head = next;
237 : }
238 0 : buf->head->read = buf->head->commit;
239 0 : buf->head->lookahead = buf->head->read;
240 :
241 0 : if (ld && ld->ops->flush_buffer)
242 0 : ld->ops->flush_buffer(tty);
243 :
244 0 : atomic_dec(&buf->priority);
245 0 : mutex_unlock(&buf->lock);
246 0 : }
247 :
248 : /**
249 : * __tty_buffer_request_room - grow tty buffer if needed
250 : * @port: tty port
251 : * @size: size desired
252 : * @flags: buffer has to store flags along character data
253 : *
254 : * Make at least @size bytes of linear space available for the tty buffer.
255 : *
256 : * Will change over to a new buffer if the current buffer is encoded as
257 : * %TTY_NORMAL (so has no flags buffer) and the new buffer requires a flags
258 : * buffer.
259 : *
260 : * Returns: the size we managed to find.
261 : */
262 0 : static int __tty_buffer_request_room(struct tty_port *port, size_t size,
263 : bool flags)
264 : {
265 0 : struct tty_bufhead *buf = &port->buf;
266 : struct tty_buffer *b, *n;
267 : int left, change;
268 :
269 0 : b = buf->tail;
270 0 : if (!b->flags)
271 0 : left = 2 * b->size - b->used;
272 : else
273 0 : left = b->size - b->used;
274 :
275 0 : change = !b->flags && flags;
276 0 : if (change || left < size) {
277 : /* This is the slow path - looking for new buffers to use */
278 0 : n = tty_buffer_alloc(port, size);
279 0 : if (n != NULL) {
280 0 : n->flags = flags;
281 0 : buf->tail = n;
282 : /*
283 : * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
284 : * ensures they see all buffer data.
285 : */
286 0 : smp_store_release(&b->commit, b->used);
287 : /*
288 : * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
289 : * ensures the latest commit value can be read before the head
290 : * is advanced to the next buffer.
291 : */
292 0 : smp_store_release(&b->next, n);
293 0 : } else if (change)
294 : size = 0;
295 : else
296 0 : size = left;
297 : }
298 0 : return size;
299 : }
300 :
301 0 : int tty_buffer_request_room(struct tty_port *port, size_t size)
302 : {
303 0 : return __tty_buffer_request_room(port, size, true);
304 : }
305 : EXPORT_SYMBOL_GPL(tty_buffer_request_room);
306 :
307 : /**
308 : * tty_insert_flip_string_fixed_flag - add characters to the tty buffer
309 : * @port: tty port
310 : * @chars: characters
311 : * @flag: flag value for each character
312 : * @size: size
313 : *
314 : * Queue a series of bytes to the tty buffering. All the characters passed are
315 : * marked with the supplied flag.
316 : *
317 : * Returns: the number added.
318 : */
319 0 : int tty_insert_flip_string_fixed_flag(struct tty_port *port,
320 : const unsigned char *chars, char flag, size_t size)
321 : {
322 0 : int copied = 0;
323 0 : bool flags = flag != TTY_NORMAL;
324 :
325 : do {
326 0 : int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
327 0 : int space = __tty_buffer_request_room(port, goal, flags);
328 0 : struct tty_buffer *tb = port->buf.tail;
329 :
330 0 : if (unlikely(space == 0))
331 : break;
332 0 : memcpy(char_buf_ptr(tb, tb->used), chars, space);
333 0 : if (tb->flags)
334 0 : memset(flag_buf_ptr(tb, tb->used), flag, space);
335 0 : tb->used += space;
336 0 : copied += space;
337 0 : chars += space;
338 : /* There is a small chance that we need to split the data over
339 : * several buffers. If this is the case we must loop.
340 : */
341 0 : } while (unlikely(size > copied));
342 0 : return copied;
343 : }
344 : EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
345 :
346 : /**
347 : * tty_insert_flip_string_flags - add characters to the tty buffer
348 : * @port: tty port
349 : * @chars: characters
350 : * @flags: flag bytes
351 : * @size: size
352 : *
353 : * Queue a series of bytes to the tty buffering. For each character the flags
354 : * array indicates the status of the character.
355 : *
356 : * Returns: the number added.
357 : */
358 0 : int tty_insert_flip_string_flags(struct tty_port *port,
359 : const unsigned char *chars, const char *flags, size_t size)
360 : {
361 0 : int copied = 0;
362 :
363 : do {
364 0 : int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
365 0 : int space = tty_buffer_request_room(port, goal);
366 0 : struct tty_buffer *tb = port->buf.tail;
367 :
368 0 : if (unlikely(space == 0))
369 : break;
370 0 : memcpy(char_buf_ptr(tb, tb->used), chars, space);
371 0 : memcpy(flag_buf_ptr(tb, tb->used), flags, space);
372 0 : tb->used += space;
373 0 : copied += space;
374 0 : chars += space;
375 0 : flags += space;
376 : /* There is a small chance that we need to split the data over
377 : * several buffers. If this is the case we must loop.
378 : */
379 0 : } while (unlikely(size > copied));
380 0 : return copied;
381 : }
382 : EXPORT_SYMBOL(tty_insert_flip_string_flags);
383 :
384 : /**
385 : * __tty_insert_flip_char - add one character to the tty buffer
386 : * @port: tty port
387 : * @ch: character
388 : * @flag: flag byte
389 : *
390 : * Queue a single byte @ch to the tty buffering, with an optional flag. This is
391 : * the slow path of tty_insert_flip_char().
392 : */
393 0 : int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
394 : {
395 : struct tty_buffer *tb;
396 0 : bool flags = flag != TTY_NORMAL;
397 :
398 0 : if (!__tty_buffer_request_room(port, 1, flags))
399 : return 0;
400 :
401 0 : tb = port->buf.tail;
402 0 : if (tb->flags)
403 0 : *flag_buf_ptr(tb, tb->used) = flag;
404 0 : *char_buf_ptr(tb, tb->used++) = ch;
405 :
406 0 : return 1;
407 : }
408 : EXPORT_SYMBOL(__tty_insert_flip_char);
409 :
410 : /**
411 : * tty_prepare_flip_string - make room for characters
412 : * @port: tty port
413 : * @chars: return pointer for character write area
414 : * @size: desired size
415 : *
416 : * Prepare a block of space in the buffer for data.
417 : *
418 : * This is used for drivers that need their own block copy routines into the
419 : * buffer. There is no guarantee the buffer is a DMA target!
420 : *
421 : * Returns: the length available and buffer pointer (@chars) to the space which
422 : * is now allocated and accounted for as ready for normal characters.
423 : */
424 0 : int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
425 : size_t size)
426 : {
427 0 : int space = __tty_buffer_request_room(port, size, false);
428 :
429 0 : if (likely(space)) {
430 0 : struct tty_buffer *tb = port->buf.tail;
431 :
432 0 : *chars = char_buf_ptr(tb, tb->used);
433 0 : if (tb->flags)
434 0 : memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
435 0 : tb->used += space;
436 : }
437 0 : return space;
438 : }
439 : EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
440 :
441 : /**
442 : * tty_ldisc_receive_buf - forward data to line discipline
443 : * @ld: line discipline to process input
444 : * @p: char buffer
445 : * @f: %TTY_NORMAL, %TTY_BREAK, etc. flags buffer
446 : * @count: number of bytes to process
447 : *
448 : * Callers other than flush_to_ldisc() need to exclude the kworker from
449 : * concurrent use of the line discipline, see paste_selection().
450 : *
451 : * Returns: the number of bytes processed.
452 : */
453 0 : int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
454 : const char *f, int count)
455 : {
456 0 : if (ld->ops->receive_buf2)
457 0 : count = ld->ops->receive_buf2(ld->tty, p, f, count);
458 : else {
459 0 : count = min_t(int, count, ld->tty->receive_room);
460 0 : if (count && ld->ops->receive_buf)
461 0 : ld->ops->receive_buf(ld->tty, p, f, count);
462 : }
463 0 : return count;
464 : }
465 : EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);
466 :
467 0 : static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
468 : {
469 0 : head->lookahead = max(head->lookahead, head->read);
470 :
471 0 : while (head) {
472 : struct tty_buffer *next;
473 : unsigned int count;
474 :
475 : /*
476 : * Paired w/ release in __tty_buffer_request_room();
477 : * ensures commit value read is not stale if the head
478 : * is advancing to the next buffer.
479 : */
480 0 : next = smp_load_acquire(&head->next);
481 : /*
482 : * Paired w/ release in __tty_buffer_request_room() or in
483 : * tty_buffer_flush(); ensures we see the committed buffer data.
484 : */
485 0 : count = smp_load_acquire(&head->commit) - head->lookahead;
486 0 : if (!count) {
487 0 : head = next;
488 0 : continue;
489 : }
490 :
491 0 : if (port->client_ops->lookahead_buf) {
492 0 : unsigned char *p, *f = NULL;
493 :
494 0 : p = char_buf_ptr(head, head->lookahead);
495 0 : if (head->flags)
496 0 : f = flag_buf_ptr(head, head->lookahead);
497 :
498 0 : port->client_ops->lookahead_buf(port, p, f, count);
499 : }
500 :
501 0 : head->lookahead += count;
502 : }
503 0 : }
504 :
505 : static int
506 0 : receive_buf(struct tty_port *port, struct tty_buffer *head, int count)
507 : {
508 0 : unsigned char *p = char_buf_ptr(head, head->read);
509 0 : const char *f = NULL;
510 : int n;
511 :
512 0 : if (head->flags)
513 0 : f = flag_buf_ptr(head, head->read);
514 :
515 0 : n = port->client_ops->receive_buf(port, p, f, count);
516 0 : if (n > 0)
517 0 : memset(p, 0, n);
518 0 : return n;
519 : }
520 :
521 : /**
522 : * flush_to_ldisc - flush data from buffer to ldisc
523 : * @work: tty structure passed from work queue.
524 : *
525 : * This routine is called out of the software interrupt to flush data from the
526 : * buffer chain to the line discipline.
527 : *
528 : * The receive_buf() method is single threaded for each tty instance.
529 : *
530 : * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
531 : */
532 0 : static void flush_to_ldisc(struct work_struct *work)
533 : {
534 0 : struct tty_port *port = container_of(work, struct tty_port, buf.work);
535 0 : struct tty_bufhead *buf = &port->buf;
536 :
537 0 : mutex_lock(&buf->lock);
538 :
539 : while (1) {
540 0 : struct tty_buffer *head = buf->head;
541 : struct tty_buffer *next;
542 : int count, rcvd;
543 :
544 : /* Ldisc or user is trying to gain exclusive access */
545 0 : if (atomic_read(&buf->priority))
546 : break;
547 :
548 : /* paired w/ release in __tty_buffer_request_room();
549 : * ensures commit value read is not stale if the head
550 : * is advancing to the next buffer
551 : */
552 0 : next = smp_load_acquire(&head->next);
553 : /* paired w/ release in __tty_buffer_request_room() or in
554 : * tty_buffer_flush(); ensures we see the committed buffer data
555 : */
556 0 : count = smp_load_acquire(&head->commit) - head->read;
557 0 : if (!count) {
558 0 : if (next == NULL)
559 : break;
560 0 : buf->head = next;
561 0 : tty_buffer_free(port, head);
562 0 : continue;
563 : }
564 :
565 0 : rcvd = receive_buf(port, head, count);
566 0 : head->read += rcvd;
567 0 : if (rcvd < count)
568 0 : lookahead_bufs(port, head);
569 0 : if (!rcvd)
570 : break;
571 :
572 0 : if (need_resched())
573 0 : cond_resched();
574 : }
575 :
576 0 : mutex_unlock(&buf->lock);
577 :
578 0 : }
579 :
580 : static inline void tty_flip_buffer_commit(struct tty_buffer *tail)
581 : {
582 : /*
583 : * Paired w/ acquire in flush_to_ldisc(); ensures flush_to_ldisc() sees
584 : * buffer data.
585 : */
586 0 : smp_store_release(&tail->commit, tail->used);
587 : }
588 :
589 : /**
590 : * tty_flip_buffer_push - push terminal buffers
591 : * @port: tty port to push
592 : *
593 : * Queue a push of the terminal flip buffers to the line discipline. Can be
594 : * called from IRQ/atomic context.
595 : *
596 : * In the event of the queue being busy for flipping the work will be held off
597 : * and retried later.
598 : */
599 0 : void tty_flip_buffer_push(struct tty_port *port)
600 : {
601 0 : struct tty_bufhead *buf = &port->buf;
602 :
603 0 : tty_flip_buffer_commit(buf->tail);
604 0 : queue_work(system_unbound_wq, &buf->work);
605 0 : }
606 : EXPORT_SYMBOL(tty_flip_buffer_push);
607 :
608 : /**
609 : * tty_insert_flip_string_and_push_buffer - add characters to the tty buffer and
610 : * push
611 : * @port: tty port
612 : * @chars: characters
613 : * @size: size
614 : *
615 : * The function combines tty_insert_flip_string() and tty_flip_buffer_push()
616 : * with the exception of properly holding the @port->lock.
617 : *
618 : * To be used only internally (by pty currently).
619 : *
620 : * Returns: the number added.
621 : */
622 0 : int tty_insert_flip_string_and_push_buffer(struct tty_port *port,
623 : const unsigned char *chars, size_t size)
624 : {
625 0 : struct tty_bufhead *buf = &port->buf;
626 : unsigned long flags;
627 :
628 0 : spin_lock_irqsave(&port->lock, flags);
629 0 : size = tty_insert_flip_string(port, chars, size);
630 0 : if (size)
631 0 : tty_flip_buffer_commit(buf->tail);
632 0 : spin_unlock_irqrestore(&port->lock, flags);
633 :
634 0 : queue_work(system_unbound_wq, &buf->work);
635 :
636 0 : return size;
637 : }
638 :
639 : /**
640 : * tty_buffer_init - prepare a tty buffer structure
641 : * @port: tty port to initialise
642 : *
643 : * Set up the initial state of the buffer management for a tty device. Must be
644 : * called before the other tty buffer functions are used.
645 : */
646 16 : void tty_buffer_init(struct tty_port *port)
647 : {
648 16 : struct tty_bufhead *buf = &port->buf;
649 :
650 16 : mutex_init(&buf->lock);
651 32 : tty_buffer_reset(&buf->sentinel, 0);
652 16 : buf->head = &buf->sentinel;
653 16 : buf->tail = &buf->sentinel;
654 32 : init_llist_head(&buf->free);
655 32 : atomic_set(&buf->mem_used, 0);
656 32 : atomic_set(&buf->priority, 0);
657 32 : INIT_WORK(&buf->work, flush_to_ldisc);
658 16 : buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
659 16 : }
660 :
661 : /**
662 : * tty_buffer_set_limit - change the tty buffer memory limit
663 : * @port: tty port to change
664 : * @limit: memory limit to set
665 : *
666 : * Change the tty buffer memory limit.
667 : *
668 : * Must be called before the other tty buffer functions are used.
669 : */
670 0 : int tty_buffer_set_limit(struct tty_port *port, int limit)
671 : {
672 0 : if (limit < MIN_TTYB_SIZE)
673 : return -EINVAL;
674 0 : port->buf.mem_limit = limit;
675 0 : return 0;
676 : }
677 : EXPORT_SYMBOL_GPL(tty_buffer_set_limit);
678 :
679 : /* slave ptys can claim nested buffer lock when handling BRK and INTR */
680 0 : void tty_buffer_set_lock_subclass(struct tty_port *port)
681 : {
682 : lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
683 0 : }
684 :
685 0 : bool tty_buffer_restart_work(struct tty_port *port)
686 : {
687 0 : return queue_work(system_unbound_wq, &port->buf.work);
688 : }
689 :
690 0 : bool tty_buffer_cancel_work(struct tty_port *port)
691 : {
692 0 : return cancel_work_sync(&port->buf.work);
693 : }
694 :
695 0 : void tty_buffer_flush_work(struct tty_port *port)
696 : {
697 0 : flush_work(&port->buf.work);
698 0 : }
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