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Commit | Line | Data |
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e0495736 AC |
1 | /* |
2 | * Tty buffer allocation management | |
3 | */ | |
4 | ||
5 | #include <linux/types.h> | |
6 | #include <linux/errno.h> | |
7 | #include <linux/tty.h> | |
8 | #include <linux/tty_driver.h> | |
9 | #include <linux/tty_flip.h> | |
10 | #include <linux/timer.h> | |
11 | #include <linux/string.h> | |
12 | #include <linux/slab.h> | |
13 | #include <linux/sched.h> | |
e0495736 AC |
14 | #include <linux/wait.h> |
15 | #include <linux/bitops.h> | |
16 | #include <linux/delay.h> | |
17 | #include <linux/module.h> | |
593fb1ae | 18 | #include <linux/ratelimit.h> |
e0495736 | 19 | |
1cef50e3 PH |
20 | |
21 | #define MIN_TTYB_SIZE 256 | |
22 | #define TTYB_ALIGN_MASK 255 | |
23 | ||
7bfe0b71 PH |
24 | /* |
25 | * Byte threshold to limit memory consumption for flip buffers. | |
26 | * The actual memory limit is > 2x this amount. | |
27 | */ | |
4d18e6ef | 28 | #define TTYB_DEFAULT_MEM_LIMIT 65536 |
7bfe0b71 | 29 | |
9114fe8c PH |
30 | /* |
31 | * We default to dicing tty buffer allocations to this many characters | |
32 | * in order to avoid multiple page allocations. We know the size of | |
33 | * tty_buffer itself but it must also be taken into account that the | |
34 | * the buffer is 256 byte aligned. See tty_buffer_find for the allocation | |
35 | * logic this must match | |
36 | */ | |
37 | ||
38 | #define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF) | |
39 | ||
a7c8d58c PH |
40 | /** |
41 | * tty_buffer_lock_exclusive - gain exclusive access to buffer | |
42 | * tty_buffer_unlock_exclusive - release exclusive access | |
43 | * | |
44 | * @port - tty_port owning the flip buffer | |
45 | * | |
46 | * Guarantees safe use of the line discipline's receive_buf() method by | |
47 | * excluding the buffer work and any pending flush from using the flip | |
48 | * buffer. Data can continue to be added concurrently to the flip buffer | |
49 | * from the driver side. | |
50 | * | |
51 | * On release, the buffer work is restarted if there is data in the | |
52 | * flip buffer | |
53 | */ | |
54 | ||
55 | void tty_buffer_lock_exclusive(struct tty_port *port) | |
56 | { | |
57 | struct tty_bufhead *buf = &port->buf; | |
58 | ||
59 | atomic_inc(&buf->priority); | |
60 | mutex_lock(&buf->lock); | |
61 | } | |
28a821c3 | 62 | EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive); |
a7c8d58c PH |
63 | |
64 | void tty_buffer_unlock_exclusive(struct tty_port *port) | |
65 | { | |
66 | struct tty_bufhead *buf = &port->buf; | |
67 | int restart; | |
68 | ||
69 | restart = buf->head->commit != buf->head->read; | |
70 | ||
71 | atomic_dec(&buf->priority); | |
72 | mutex_unlock(&buf->lock); | |
73 | if (restart) | |
74 | queue_work(system_unbound_wq, &buf->work); | |
75 | } | |
28a821c3 | 76 | EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive); |
a7c8d58c | 77 | |
7bfe0b71 PH |
78 | /** |
79 | * tty_buffer_space_avail - return unused buffer space | |
80 | * @port - tty_port owning the flip buffer | |
81 | * | |
82 | * Returns the # of bytes which can be written by the driver without | |
83 | * reaching the buffer limit. | |
84 | * | |
85 | * Note: this does not guarantee that memory is available to write | |
86 | * the returned # of bytes (use tty_prepare_flip_string_xxx() to | |
87 | * pre-allocate if memory guarantee is required). | |
88 | */ | |
89 | ||
90 | int tty_buffer_space_avail(struct tty_port *port) | |
91 | { | |
5dda4ca5 | 92 | int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used); |
7bfe0b71 PH |
93 | return max(space, 0); |
94 | } | |
c4a8dab5 | 95 | EXPORT_SYMBOL_GPL(tty_buffer_space_avail); |
7bfe0b71 | 96 | |
9dd5139f PH |
97 | static void tty_buffer_reset(struct tty_buffer *p, size_t size) |
98 | { | |
99 | p->used = 0; | |
100 | p->size = size; | |
101 | p->next = NULL; | |
102 | p->commit = 0; | |
103 | p->read = 0; | |
acc0f67f | 104 | p->flags = 0; |
9dd5139f PH |
105 | } |
106 | ||
e0495736 AC |
107 | /** |
108 | * tty_buffer_free_all - free buffers used by a tty | |
109 | * @tty: tty to free from | |
110 | * | |
111 | * Remove all the buffers pending on a tty whether queued with data | |
112 | * or in the free ring. Must be called when the tty is no longer in use | |
e0495736 AC |
113 | */ |
114 | ||
ecbbfd44 | 115 | void tty_buffer_free_all(struct tty_port *port) |
e0495736 | 116 | { |
ecbbfd44 | 117 | struct tty_bufhead *buf = &port->buf; |
809850b7 PH |
118 | struct tty_buffer *p, *next; |
119 | struct llist_node *llist; | |
5cff39c6 | 120 | |
2cf7b67e PH |
121 | while ((p = buf->head) != NULL) { |
122 | buf->head = p->next; | |
7391ee16 PH |
123 | if (p->size > 0) |
124 | kfree(p); | |
e0495736 | 125 | } |
809850b7 PH |
126 | llist = llist_del_all(&buf->free); |
127 | llist_for_each_entry_safe(p, next, llist, free) | |
2cf7b67e | 128 | kfree(p); |
809850b7 | 129 | |
7391ee16 PH |
130 | tty_buffer_reset(&buf->sentinel, 0); |
131 | buf->head = &buf->sentinel; | |
132 | buf->tail = &buf->sentinel; | |
7bfe0b71 | 133 | |
5dda4ca5 | 134 | atomic_set(&buf->mem_used, 0); |
e0495736 AC |
135 | } |
136 | ||
137 | /** | |
138 | * tty_buffer_alloc - allocate a tty buffer | |
139 | * @tty: tty device | |
140 | * @size: desired size (characters) | |
141 | * | |
142 | * Allocate a new tty buffer to hold the desired number of characters. | |
11b9faa4 PH |
143 | * We round our buffers off in 256 character chunks to get better |
144 | * allocation behaviour. | |
e0495736 AC |
145 | * Return NULL if out of memory or the allocation would exceed the |
146 | * per device queue | |
e0495736 AC |
147 | */ |
148 | ||
ecbbfd44 | 149 | static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) |
e0495736 | 150 | { |
809850b7 | 151 | struct llist_node *free; |
e0495736 AC |
152 | struct tty_buffer *p; |
153 | ||
11b9faa4 PH |
154 | /* Round the buffer size out */ |
155 | size = __ALIGN_MASK(size, TTYB_ALIGN_MASK); | |
156 | ||
157 | if (size <= MIN_TTYB_SIZE) { | |
809850b7 PH |
158 | free = llist_del_first(&port->buf.free); |
159 | if (free) { | |
160 | p = llist_entry(free, struct tty_buffer, free); | |
11b9faa4 PH |
161 | goto found; |
162 | } | |
163 | } | |
164 | ||
165 | /* Should possibly check if this fails for the largest buffer we | |
166 | have queued and recycle that ? */ | |
5dda4ca5 | 167 | if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit) |
e0495736 AC |
168 | return NULL; |
169 | p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); | |
170 | if (p == NULL) | |
171 | return NULL; | |
9dd5139f | 172 | |
11b9faa4 | 173 | found: |
9dd5139f | 174 | tty_buffer_reset(p, size); |
5dda4ca5 | 175 | atomic_add(size, &port->buf.mem_used); |
e0495736 AC |
176 | return p; |
177 | } | |
178 | ||
179 | /** | |
180 | * tty_buffer_free - free a tty buffer | |
181 | * @tty: tty owning the buffer | |
182 | * @b: the buffer to free | |
183 | * | |
184 | * Free a tty buffer, or add it to the free list according to our | |
185 | * internal strategy | |
e0495736 AC |
186 | */ |
187 | ||
ecbbfd44 | 188 | static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) |
e0495736 | 189 | { |
ecbbfd44 | 190 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 191 | |
e0495736 | 192 | /* Dumb strategy for now - should keep some stats */ |
5dda4ca5 | 193 | WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0); |
e0495736 | 194 | |
1cef50e3 | 195 | if (b->size > MIN_TTYB_SIZE) |
e0495736 | 196 | kfree(b); |
7391ee16 | 197 | else if (b->size > 0) |
809850b7 | 198 | llist_add(&b->free, &buf->free); |
e0495736 AC |
199 | } |
200 | ||
e0495736 AC |
201 | /** |
202 | * tty_buffer_flush - flush full tty buffers | |
203 | * @tty: tty to flush | |
86c80a8e | 204 | * @ld: optional ldisc ptr (must be referenced) |
e0495736 | 205 | * |
86c80a8e PH |
206 | * flush all the buffers containing receive data. If ld != NULL, |
207 | * flush the ldisc input buffer. | |
e0495736 | 208 | * |
a7c8d58c | 209 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 210 | * 'consumer' |
e0495736 AC |
211 | */ |
212 | ||
86c80a8e | 213 | void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld) |
e0495736 | 214 | { |
2fc20661 | 215 | struct tty_port *port = tty->port; |
ecbbfd44 | 216 | struct tty_bufhead *buf = &port->buf; |
47aa658a | 217 | struct tty_buffer *next; |
e0495736 | 218 | |
a7c8d58c | 219 | atomic_inc(&buf->priority); |
e9975fde | 220 | |
a7c8d58c | 221 | mutex_lock(&buf->lock); |
9e6b7cd7 DV |
222 | /* paired w/ release in __tty_buffer_request_room; ensures there are |
223 | * no pending memory accesses to the freed buffer | |
224 | */ | |
225 | while ((next = smp_load_acquire(&buf->head->next)) != NULL) { | |
47aa658a PH |
226 | tty_buffer_free(port, buf->head); |
227 | buf->head = next; | |
228 | } | |
229 | buf->head->read = buf->head->commit; | |
86c80a8e PH |
230 | |
231 | if (ld && ld->ops->flush_buffer) | |
232 | ld->ops->flush_buffer(tty); | |
233 | ||
a7c8d58c PH |
234 | atomic_dec(&buf->priority); |
235 | mutex_unlock(&buf->lock); | |
e0495736 AC |
236 | } |
237 | ||
e0495736 | 238 | /** |
64325a3b | 239 | * tty_buffer_request_room - grow tty buffer if needed |
e0495736 AC |
240 | * @tty: tty structure |
241 | * @size: size desired | |
acc0f67f | 242 | * @flags: buffer flags if new buffer allocated (default = 0) |
e0495736 AC |
243 | * |
244 | * Make at least size bytes of linear space available for the tty | |
245 | * buffer. If we fail return the size we managed to find. | |
acc0f67f PH |
246 | * |
247 | * Will change over to a new buffer if the current buffer is encoded as | |
248 | * TTY_NORMAL (so has no flags buffer) and the new buffer requires | |
249 | * a flags buffer. | |
e0495736 | 250 | */ |
acc0f67f PH |
251 | static int __tty_buffer_request_room(struct tty_port *port, size_t size, |
252 | int flags) | |
e0495736 | 253 | { |
ecbbfd44 | 254 | struct tty_bufhead *buf = &port->buf; |
e0495736 | 255 | struct tty_buffer *b, *n; |
acc0f67f | 256 | int left, change; |
e8437d7e | 257 | |
5cff39c6 | 258 | b = buf->tail; |
acc0f67f PH |
259 | if (b->flags & TTYB_NORMAL) |
260 | left = 2 * b->size - b->used; | |
261 | else | |
262 | left = b->size - b->used; | |
e0495736 | 263 | |
acc0f67f PH |
264 | change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL); |
265 | if (change || left < size) { | |
e0495736 | 266 | /* This is the slow path - looking for new buffers to use */ |
e16cb0a7 GKH |
267 | n = tty_buffer_alloc(port, size); |
268 | if (n != NULL) { | |
acc0f67f | 269 | n->flags = flags; |
5cff39c6 | 270 | buf->tail = n; |
facd885c DV |
271 | /* paired w/ acquire in flush_to_ldisc(); ensures |
272 | * flush_to_ldisc() sees buffer data. | |
273 | */ | |
274 | smp_store_release(&b->commit, b->used); | |
069f38b4 | 275 | /* paired w/ acquire in flush_to_ldisc(); ensures the |
62a0d8d7 PH |
276 | * latest commit value can be read before the head is |
277 | * advanced to the next buffer | |
278 | */ | |
069f38b4 | 279 | smp_store_release(&b->next, n); |
acc0f67f PH |
280 | } else if (change) |
281 | size = 0; | |
282 | else | |
e0495736 AC |
283 | size = left; |
284 | } | |
e0495736 AC |
285 | return size; |
286 | } | |
acc0f67f PH |
287 | |
288 | int tty_buffer_request_room(struct tty_port *port, size_t size) | |
289 | { | |
290 | return __tty_buffer_request_room(port, size, 0); | |
291 | } | |
e0495736 AC |
292 | EXPORT_SYMBOL_GPL(tty_buffer_request_room); |
293 | ||
294 | /** | |
2832fc11 | 295 | * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer |
2f693357 | 296 | * @port: tty port |
e0495736 | 297 | * @chars: characters |
2832fc11 | 298 | * @flag: flag value for each character |
e0495736 AC |
299 | * @size: size |
300 | * | |
301 | * Queue a series of bytes to the tty buffering. All the characters | |
ccc5ca8d | 302 | * passed are marked with the supplied flag. Returns the number added. |
e0495736 AC |
303 | */ |
304 | ||
2f693357 | 305 | int tty_insert_flip_string_fixed_flag(struct tty_port *port, |
2832fc11 | 306 | const unsigned char *chars, char flag, size_t size) |
e0495736 AC |
307 | { |
308 | int copied = 0; | |
309 | do { | |
d4bee0a6 | 310 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
acc0f67f PH |
311 | int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; |
312 | int space = __tty_buffer_request_room(port, goal, flags); | |
64325a3b | 313 | struct tty_buffer *tb = port->buf.tail; |
7391ee16 | 314 | if (unlikely(space == 0)) |
e0495736 | 315 | break; |
1fc359fc | 316 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
acc0f67f PH |
317 | if (~tb->flags & TTYB_NORMAL) |
318 | memset(flag_buf_ptr(tb, tb->used), flag, space); | |
e0495736 AC |
319 | tb->used += space; |
320 | copied += space; | |
321 | chars += space; | |
322 | /* There is a small chance that we need to split the data over | |
323 | several buffers. If this is the case we must loop */ | |
324 | } while (unlikely(size > copied)); | |
325 | return copied; | |
326 | } | |
2832fc11 | 327 | EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag); |
e0495736 AC |
328 | |
329 | /** | |
330 | * tty_insert_flip_string_flags - Add characters to the tty buffer | |
2f693357 | 331 | * @port: tty port |
e0495736 AC |
332 | * @chars: characters |
333 | * @flags: flag bytes | |
334 | * @size: size | |
335 | * | |
336 | * Queue a series of bytes to the tty buffering. For each character | |
337 | * the flags array indicates the status of the character. Returns the | |
338 | * number added. | |
e0495736 AC |
339 | */ |
340 | ||
2f693357 | 341 | int tty_insert_flip_string_flags(struct tty_port *port, |
e0495736 AC |
342 | const unsigned char *chars, const char *flags, size_t size) |
343 | { | |
344 | int copied = 0; | |
345 | do { | |
d4bee0a6 | 346 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
64325a3b IZ |
347 | int space = tty_buffer_request_room(port, goal); |
348 | struct tty_buffer *tb = port->buf.tail; | |
7391ee16 | 349 | if (unlikely(space == 0)) |
e0495736 | 350 | break; |
1fc359fc PH |
351 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
352 | memcpy(flag_buf_ptr(tb, tb->used), flags, space); | |
e0495736 AC |
353 | tb->used += space; |
354 | copied += space; | |
355 | chars += space; | |
356 | flags += space; | |
357 | /* There is a small chance that we need to split the data over | |
358 | several buffers. If this is the case we must loop */ | |
359 | } while (unlikely(size > copied)); | |
360 | return copied; | |
361 | } | |
362 | EXPORT_SYMBOL(tty_insert_flip_string_flags); | |
363 | ||
14f73def AB |
364 | /** |
365 | * __tty_insert_flip_char - Add one character to the tty buffer | |
366 | * @port: tty port | |
367 | * @ch: character | |
368 | * @flag: flag byte | |
369 | * | |
370 | * Queue a single byte to the tty buffering, with an optional flag. | |
371 | * This is the slow path of tty_insert_flip_char. | |
372 | */ | |
373 | int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag) | |
374 | { | |
7f94c64f | 375 | struct tty_buffer *tb; |
14f73def AB |
376 | int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; |
377 | ||
97a97d66 | 378 | if (!__tty_buffer_request_room(port, 1, flags)) |
14f73def AB |
379 | return 0; |
380 | ||
7f94c64f | 381 | tb = port->buf.tail; |
97a97d66 AB |
382 | if (~tb->flags & TTYB_NORMAL) |
383 | *flag_buf_ptr(tb, tb->used) = flag; | |
14f73def AB |
384 | *char_buf_ptr(tb, tb->used++) = ch; |
385 | ||
386 | return 1; | |
387 | } | |
388 | EXPORT_SYMBOL(__tty_insert_flip_char); | |
389 | ||
e0495736 AC |
390 | /** |
391 | * tty_schedule_flip - push characters to ldisc | |
6732c8bb | 392 | * @port: tty port to push from |
e0495736 AC |
393 | * |
394 | * Takes any pending buffers and transfers their ownership to the | |
395 | * ldisc side of the queue. It then schedules those characters for | |
396 | * processing by the line discipline. | |
e0495736 AC |
397 | */ |
398 | ||
6732c8bb | 399 | void tty_schedule_flip(struct tty_port *port) |
e0495736 | 400 | { |
6732c8bb | 401 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 402 | |
facd885c DV |
403 | /* paired w/ acquire in flush_to_ldisc(); ensures |
404 | * flush_to_ldisc() sees buffer data. | |
405 | */ | |
406 | smp_store_release(&buf->tail->commit, buf->tail->used); | |
e052c6d1 | 407 | queue_work(system_unbound_wq, &buf->work); |
e0495736 AC |
408 | } |
409 | EXPORT_SYMBOL(tty_schedule_flip); | |
410 | ||
411 | /** | |
412 | * tty_prepare_flip_string - make room for characters | |
2f693357 | 413 | * @port: tty port |
e0495736 AC |
414 | * @chars: return pointer for character write area |
415 | * @size: desired size | |
416 | * | |
417 | * Prepare a block of space in the buffer for data. Returns the length | |
418 | * available and buffer pointer to the space which is now allocated and | |
419 | * accounted for as ready for normal characters. This is used for drivers | |
420 | * that need their own block copy routines into the buffer. There is no | |
421 | * guarantee the buffer is a DMA target! | |
e0495736 AC |
422 | */ |
423 | ||
2f693357 | 424 | int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars, |
ecbbfd44 | 425 | size_t size) |
e0495736 | 426 | { |
acc0f67f | 427 | int space = __tty_buffer_request_room(port, size, TTYB_NORMAL); |
e0495736 | 428 | if (likely(space)) { |
64325a3b | 429 | struct tty_buffer *tb = port->buf.tail; |
1fc359fc | 430 | *chars = char_buf_ptr(tb, tb->used); |
acc0f67f PH |
431 | if (~tb->flags & TTYB_NORMAL) |
432 | memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space); | |
e0495736 AC |
433 | tb->used += space; |
434 | } | |
435 | return space; | |
436 | } | |
437 | EXPORT_SYMBOL_GPL(tty_prepare_flip_string); | |
438 | ||
8d082cd3 PH |
439 | /** |
440 | * tty_ldisc_receive_buf - forward data to line discipline | |
441 | * @ld: line discipline to process input | |
442 | * @p: char buffer | |
443 | * @f: TTY_* flags buffer | |
444 | * @count: number of bytes to process | |
445 | * | |
446 | * Callers other than flush_to_ldisc() need to exclude the kworker | |
447 | * from concurrent use of the line discipline, see paste_selection(). | |
448 | * | |
449 | * Returns the number of bytes not processed | |
450 | */ | |
c92d781f | 451 | int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p, |
8d082cd3 PH |
452 | char *f, int count) |
453 | { | |
454 | if (ld->ops->receive_buf2) | |
455 | count = ld->ops->receive_buf2(ld->tty, p, f, count); | |
456 | else { | |
457 | count = min_t(int, count, ld->tty->receive_room); | |
458 | if (count && ld->ops->receive_buf) | |
459 | ld->ops->receive_buf(ld->tty, p, f, count); | |
460 | } | |
461 | return count; | |
462 | } | |
463 | EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf); | |
e0495736 | 464 | |
da261e7f | 465 | static int |
c3485ee0 | 466 | receive_buf(struct tty_port *port, struct tty_buffer *head, int count) |
da261e7f | 467 | { |
1fc359fc | 468 | unsigned char *p = char_buf_ptr(head, head->read); |
acc0f67f PH |
469 | char *f = NULL; |
470 | ||
471 | if (~head->flags & TTYB_NORMAL) | |
472 | f = flag_buf_ptr(head, head->read); | |
da261e7f | 473 | |
c3485ee0 | 474 | return port->client_ops->receive_buf(port, p, f, count); |
da261e7f | 475 | } |
e0495736 AC |
476 | |
477 | /** | |
478 | * flush_to_ldisc | |
479 | * @work: tty structure passed from work queue. | |
480 | * | |
481 | * This routine is called out of the software interrupt to flush data | |
482 | * from the buffer chain to the line discipline. | |
483 | * | |
e9975fde PH |
484 | * The receive_buf method is single threaded for each tty instance. |
485 | * | |
a7c8d58c | 486 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 487 | * 'consumer' |
e0495736 AC |
488 | */ |
489 | ||
490 | static void flush_to_ldisc(struct work_struct *work) | |
491 | { | |
ecbbfd44 JS |
492 | struct tty_port *port = container_of(work, struct tty_port, buf.work); |
493 | struct tty_bufhead *buf = &port->buf; | |
e0495736 | 494 | |
a7c8d58c | 495 | mutex_lock(&buf->lock); |
45242006 | 496 | |
d7a68be4 PH |
497 | while (1) { |
498 | struct tty_buffer *head = buf->head; | |
62a0d8d7 | 499 | struct tty_buffer *next; |
d7a68be4 PH |
500 | int count; |
501 | ||
a7c8d58c PH |
502 | /* Ldisc or user is trying to gain exclusive access */ |
503 | if (atomic_read(&buf->priority)) | |
d7a68be4 PH |
504 | break; |
505 | ||
069f38b4 | 506 | /* paired w/ release in __tty_buffer_request_room(); |
62a0d8d7 PH |
507 | * ensures commit value read is not stale if the head |
508 | * is advancing to the next buffer | |
509 | */ | |
069f38b4 | 510 | next = smp_load_acquire(&head->next); |
facd885c DV |
511 | /* paired w/ release in __tty_buffer_request_room() or in |
512 | * tty_buffer_flush(); ensures we see the committed buffer data | |
513 | */ | |
514 | count = smp_load_acquire(&head->commit) - head->read; | |
d7a68be4 | 515 | if (!count) { |
0f40fbbc | 516 | if (next == NULL) |
da261e7f | 517 | break; |
62a0d8d7 | 518 | buf->head = next; |
d7a68be4 PH |
519 | tty_buffer_free(port, head); |
520 | continue; | |
e0495736 | 521 | } |
d7a68be4 | 522 | |
c3485ee0 | 523 | count = receive_buf(port, head, count); |
d7a68be4 PH |
524 | if (!count) |
525 | break; | |
af5554f9 | 526 | head->read += count; |
e0495736 | 527 | } |
45242006 | 528 | |
a7c8d58c | 529 | mutex_unlock(&buf->lock); |
e0495736 | 530 | |
e0495736 AC |
531 | } |
532 | ||
533 | /** | |
534 | * tty_flip_buffer_push - terminal | |
2e124b4a | 535 | * @port: tty port to push |
e0495736 | 536 | * |
a9c3f68f PH |
537 | * Queue a push of the terminal flip buffers to the line discipline. |
538 | * Can be called from IRQ/atomic context. | |
e0495736 AC |
539 | * |
540 | * In the event of the queue being busy for flipping the work will be | |
541 | * held off and retried later. | |
e0495736 AC |
542 | */ |
543 | ||
2e124b4a | 544 | void tty_flip_buffer_push(struct tty_port *port) |
e0495736 | 545 | { |
a9c3f68f | 546 | tty_schedule_flip(port); |
e0495736 AC |
547 | } |
548 | EXPORT_SYMBOL(tty_flip_buffer_push); | |
549 | ||
550 | /** | |
551 | * tty_buffer_init - prepare a tty buffer structure | |
552 | * @tty: tty to initialise | |
553 | * | |
554 | * Set up the initial state of the buffer management for a tty device. | |
555 | * Must be called before the other tty buffer functions are used. | |
e0495736 AC |
556 | */ |
557 | ||
ecbbfd44 | 558 | void tty_buffer_init(struct tty_port *port) |
e0495736 | 559 | { |
ecbbfd44 | 560 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 561 | |
a7c8d58c | 562 | mutex_init(&buf->lock); |
7391ee16 PH |
563 | tty_buffer_reset(&buf->sentinel, 0); |
564 | buf->head = &buf->sentinel; | |
565 | buf->tail = &buf->sentinel; | |
809850b7 | 566 | init_llist_head(&buf->free); |
5dda4ca5 | 567 | atomic_set(&buf->mem_used, 0); |
a7c8d58c | 568 | atomic_set(&buf->priority, 0); |
5cff39c6 | 569 | INIT_WORK(&buf->work, flush_to_ldisc); |
4d18e6ef | 570 | buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT; |
e0495736 | 571 | } |
4d18e6ef PH |
572 | |
573 | /** | |
574 | * tty_buffer_set_limit - change the tty buffer memory limit | |
575 | * @port: tty port to change | |
576 | * | |
577 | * Change the tty buffer memory limit. | |
578 | * Must be called before the other tty buffer functions are used. | |
579 | */ | |
580 | ||
581 | int tty_buffer_set_limit(struct tty_port *port, int limit) | |
582 | { | |
583 | if (limit < MIN_TTYB_SIZE) | |
584 | return -EINVAL; | |
585 | port->buf.mem_limit = limit; | |
586 | return 0; | |
587 | } | |
588 | EXPORT_SYMBOL_GPL(tty_buffer_set_limit); | |
1d1d14da PH |
589 | |
590 | /* slave ptys can claim nested buffer lock when handling BRK and INTR */ | |
591 | void tty_buffer_set_lock_subclass(struct tty_port *port) | |
592 | { | |
593 | lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE); | |
594 | } | |
e176058f PH |
595 | |
596 | bool tty_buffer_restart_work(struct tty_port *port) | |
597 | { | |
598 | return queue_work(system_unbound_wq, &port->buf.work); | |
599 | } | |
600 | ||
601 | bool tty_buffer_cancel_work(struct tty_port *port) | |
602 | { | |
603 | return cancel_work_sync(&port->buf.work); | |
604 | } | |
0f40fbbc BB |
605 | |
606 | void tty_buffer_flush_work(struct tty_port *port) | |
607 | { | |
608 | flush_work(&port->buf.work); | |
609 | } |