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e3b3d0f5 | 1 | // SPDX-License-Identifier: GPL-2.0 |
e0495736 AC |
2 | /* |
3 | * Tty buffer allocation management | |
4 | */ | |
5 | ||
6 | #include <linux/types.h> | |
7 | #include <linux/errno.h> | |
8 | #include <linux/tty.h> | |
9 | #include <linux/tty_driver.h> | |
10 | #include <linux/tty_flip.h> | |
11 | #include <linux/timer.h> | |
12 | #include <linux/string.h> | |
13 | #include <linux/slab.h> | |
14 | #include <linux/sched.h> | |
e0495736 AC |
15 | #include <linux/wait.h> |
16 | #include <linux/bitops.h> | |
17 | #include <linux/delay.h> | |
18 | #include <linux/module.h> | |
593fb1ae | 19 | #include <linux/ratelimit.h> |
6c80c0b9 | 20 | #include "tty.h" |
1cef50e3 PH |
21 | |
22 | #define MIN_TTYB_SIZE 256 | |
23 | #define TTYB_ALIGN_MASK 255 | |
24 | ||
7bfe0b71 PH |
25 | /* |
26 | * Byte threshold to limit memory consumption for flip buffers. | |
27 | * The actual memory limit is > 2x this amount. | |
28 | */ | |
7ab57b76 | 29 | #define TTYB_DEFAULT_MEM_LIMIT (640 * 1024UL) |
7bfe0b71 | 30 | |
9114fe8c PH |
31 | /* |
32 | * We default to dicing tty buffer allocations to this many characters | |
33 | * in order to avoid multiple page allocations. We know the size of | |
34 | * tty_buffer itself but it must also be taken into account that the | |
35 | * the buffer is 256 byte aligned. See tty_buffer_find for the allocation | |
36 | * logic this must match | |
37 | */ | |
38 | ||
39 | #define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF) | |
40 | ||
a7c8d58c PH |
41 | /** |
42 | * tty_buffer_lock_exclusive - gain exclusive access to buffer | |
43 | * tty_buffer_unlock_exclusive - release exclusive access | |
44 | * | |
fa441954 | 45 | * @port: tty port owning the flip buffer |
a7c8d58c PH |
46 | * |
47 | * Guarantees safe use of the line discipline's receive_buf() method by | |
48 | * excluding the buffer work and any pending flush from using the flip | |
49 | * buffer. Data can continue to be added concurrently to the flip buffer | |
50 | * from the driver side. | |
51 | * | |
52 | * On release, the buffer work is restarted if there is data in the | |
53 | * flip buffer | |
54 | */ | |
55 | ||
56 | void tty_buffer_lock_exclusive(struct tty_port *port) | |
57 | { | |
58 | struct tty_bufhead *buf = &port->buf; | |
59 | ||
60 | atomic_inc(&buf->priority); | |
61 | mutex_lock(&buf->lock); | |
62 | } | |
28a821c3 | 63 | EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive); |
a7c8d58c PH |
64 | |
65 | void tty_buffer_unlock_exclusive(struct tty_port *port) | |
66 | { | |
67 | struct tty_bufhead *buf = &port->buf; | |
68 | int restart; | |
69 | ||
70 | restart = buf->head->commit != buf->head->read; | |
71 | ||
72 | atomic_dec(&buf->priority); | |
73 | mutex_unlock(&buf->lock); | |
74 | if (restart) | |
75 | queue_work(system_unbound_wq, &buf->work); | |
76 | } | |
28a821c3 | 77 | EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive); |
a7c8d58c | 78 | |
7bfe0b71 PH |
79 | /** |
80 | * tty_buffer_space_avail - return unused buffer space | |
fa441954 | 81 | * @port: tty port owning the flip buffer |
7bfe0b71 PH |
82 | * |
83 | * Returns the # of bytes which can be written by the driver without | |
84 | * reaching the buffer limit. | |
85 | * | |
86 | * Note: this does not guarantee that memory is available to write | |
87 | * the returned # of bytes (use tty_prepare_flip_string_xxx() to | |
88 | * pre-allocate if memory guarantee is required). | |
89 | */ | |
90 | ||
91 | int tty_buffer_space_avail(struct tty_port *port) | |
92 | { | |
5dda4ca5 | 93 | int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used); |
7bfe0b71 PH |
94 | return max(space, 0); |
95 | } | |
c4a8dab5 | 96 | EXPORT_SYMBOL_GPL(tty_buffer_space_avail); |
7bfe0b71 | 97 | |
9dd5139f PH |
98 | static void tty_buffer_reset(struct tty_buffer *p, size_t size) |
99 | { | |
100 | p->used = 0; | |
101 | p->size = size; | |
102 | p->next = NULL; | |
103 | p->commit = 0; | |
104 | p->read = 0; | |
acc0f67f | 105 | p->flags = 0; |
9dd5139f PH |
106 | } |
107 | ||
e0495736 AC |
108 | /** |
109 | * tty_buffer_free_all - free buffers used by a tty | |
fa441954 | 110 | * @port: tty port to free from |
e0495736 AC |
111 | * |
112 | * Remove all the buffers pending on a tty whether queued with data | |
113 | * or in the free ring. Must be called when the tty is no longer in use | |
e0495736 AC |
114 | */ |
115 | ||
ecbbfd44 | 116 | void tty_buffer_free_all(struct tty_port *port) |
e0495736 | 117 | { |
ecbbfd44 | 118 | struct tty_bufhead *buf = &port->buf; |
809850b7 PH |
119 | struct tty_buffer *p, *next; |
120 | struct llist_node *llist; | |
feacbecb JS |
121 | unsigned int freed = 0; |
122 | int still_used; | |
5cff39c6 | 123 | |
2cf7b67e PH |
124 | while ((p = buf->head) != NULL) { |
125 | buf->head = p->next; | |
feacbecb | 126 | freed += p->size; |
7391ee16 PH |
127 | if (p->size > 0) |
128 | kfree(p); | |
e0495736 | 129 | } |
809850b7 PH |
130 | llist = llist_del_all(&buf->free); |
131 | llist_for_each_entry_safe(p, next, llist, free) | |
2cf7b67e | 132 | kfree(p); |
809850b7 | 133 | |
7391ee16 PH |
134 | tty_buffer_reset(&buf->sentinel, 0); |
135 | buf->head = &buf->sentinel; | |
136 | buf->tail = &buf->sentinel; | |
7bfe0b71 | 137 | |
feacbecb JS |
138 | still_used = atomic_xchg(&buf->mem_used, 0); |
139 | WARN(still_used != freed, "we still have not freed %d bytes!", | |
140 | still_used - freed); | |
e0495736 AC |
141 | } |
142 | ||
143 | /** | |
144 | * tty_buffer_alloc - allocate a tty buffer | |
fa441954 | 145 | * @port: tty port |
e0495736 AC |
146 | * @size: desired size (characters) |
147 | * | |
148 | * Allocate a new tty buffer to hold the desired number of characters. | |
11b9faa4 PH |
149 | * We round our buffers off in 256 character chunks to get better |
150 | * allocation behaviour. | |
e0495736 AC |
151 | * Return NULL if out of memory or the allocation would exceed the |
152 | * per device queue | |
e0495736 AC |
153 | */ |
154 | ||
ecbbfd44 | 155 | static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) |
e0495736 | 156 | { |
809850b7 | 157 | struct llist_node *free; |
e0495736 AC |
158 | struct tty_buffer *p; |
159 | ||
11b9faa4 PH |
160 | /* Round the buffer size out */ |
161 | size = __ALIGN_MASK(size, TTYB_ALIGN_MASK); | |
162 | ||
163 | if (size <= MIN_TTYB_SIZE) { | |
809850b7 PH |
164 | free = llist_del_first(&port->buf.free); |
165 | if (free) { | |
166 | p = llist_entry(free, struct tty_buffer, free); | |
11b9faa4 PH |
167 | goto found; |
168 | } | |
169 | } | |
170 | ||
171 | /* Should possibly check if this fails for the largest buffer we | |
172 | have queued and recycle that ? */ | |
5dda4ca5 | 173 | if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit) |
e0495736 AC |
174 | return NULL; |
175 | p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); | |
176 | if (p == NULL) | |
177 | return NULL; | |
9dd5139f | 178 | |
11b9faa4 | 179 | found: |
9dd5139f | 180 | tty_buffer_reset(p, size); |
5dda4ca5 | 181 | atomic_add(size, &port->buf.mem_used); |
e0495736 AC |
182 | return p; |
183 | } | |
184 | ||
185 | /** | |
186 | * tty_buffer_free - free a tty buffer | |
fa441954 | 187 | * @port: tty port owning the buffer |
e0495736 AC |
188 | * @b: the buffer to free |
189 | * | |
190 | * Free a tty buffer, or add it to the free list according to our | |
191 | * internal strategy | |
e0495736 AC |
192 | */ |
193 | ||
ecbbfd44 | 194 | static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) |
e0495736 | 195 | { |
ecbbfd44 | 196 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 197 | |
e0495736 | 198 | /* Dumb strategy for now - should keep some stats */ |
5dda4ca5 | 199 | WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0); |
e0495736 | 200 | |
1cef50e3 | 201 | if (b->size > MIN_TTYB_SIZE) |
e0495736 | 202 | kfree(b); |
7391ee16 | 203 | else if (b->size > 0) |
809850b7 | 204 | llist_add(&b->free, &buf->free); |
e0495736 AC |
205 | } |
206 | ||
e0495736 AC |
207 | /** |
208 | * tty_buffer_flush - flush full tty buffers | |
209 | * @tty: tty to flush | |
86c80a8e | 210 | * @ld: optional ldisc ptr (must be referenced) |
e0495736 | 211 | * |
86c80a8e PH |
212 | * flush all the buffers containing receive data. If ld != NULL, |
213 | * flush the ldisc input buffer. | |
e0495736 | 214 | * |
a7c8d58c | 215 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 216 | * 'consumer' |
e0495736 AC |
217 | */ |
218 | ||
86c80a8e | 219 | void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld) |
e0495736 | 220 | { |
2fc20661 | 221 | struct tty_port *port = tty->port; |
ecbbfd44 | 222 | struct tty_bufhead *buf = &port->buf; |
47aa658a | 223 | struct tty_buffer *next; |
e0495736 | 224 | |
a7c8d58c | 225 | atomic_inc(&buf->priority); |
e9975fde | 226 | |
a7c8d58c | 227 | mutex_lock(&buf->lock); |
9e6b7cd7 DV |
228 | /* paired w/ release in __tty_buffer_request_room; ensures there are |
229 | * no pending memory accesses to the freed buffer | |
230 | */ | |
231 | while ((next = smp_load_acquire(&buf->head->next)) != NULL) { | |
47aa658a PH |
232 | tty_buffer_free(port, buf->head); |
233 | buf->head = next; | |
234 | } | |
235 | buf->head->read = buf->head->commit; | |
86c80a8e PH |
236 | |
237 | if (ld && ld->ops->flush_buffer) | |
238 | ld->ops->flush_buffer(tty); | |
239 | ||
a7c8d58c PH |
240 | atomic_dec(&buf->priority); |
241 | mutex_unlock(&buf->lock); | |
e0495736 AC |
242 | } |
243 | ||
e0495736 | 244 | /** |
64325a3b | 245 | * tty_buffer_request_room - grow tty buffer if needed |
fa441954 | 246 | * @port: tty port |
e0495736 | 247 | * @size: size desired |
acc0f67f | 248 | * @flags: buffer flags if new buffer allocated (default = 0) |
e0495736 AC |
249 | * |
250 | * Make at least size bytes of linear space available for the tty | |
251 | * buffer. If we fail return the size we managed to find. | |
acc0f67f PH |
252 | * |
253 | * Will change over to a new buffer if the current buffer is encoded as | |
254 | * TTY_NORMAL (so has no flags buffer) and the new buffer requires | |
255 | * a flags buffer. | |
e0495736 | 256 | */ |
acc0f67f PH |
257 | static int __tty_buffer_request_room(struct tty_port *port, size_t size, |
258 | int flags) | |
e0495736 | 259 | { |
ecbbfd44 | 260 | struct tty_bufhead *buf = &port->buf; |
e0495736 | 261 | struct tty_buffer *b, *n; |
acc0f67f | 262 | int left, change; |
e8437d7e | 263 | |
5cff39c6 | 264 | b = buf->tail; |
acc0f67f PH |
265 | if (b->flags & TTYB_NORMAL) |
266 | left = 2 * b->size - b->used; | |
267 | else | |
268 | left = b->size - b->used; | |
e0495736 | 269 | |
acc0f67f PH |
270 | change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL); |
271 | if (change || left < size) { | |
e0495736 | 272 | /* This is the slow path - looking for new buffers to use */ |
e16cb0a7 GKH |
273 | n = tty_buffer_alloc(port, size); |
274 | if (n != NULL) { | |
acc0f67f | 275 | n->flags = flags; |
5cff39c6 | 276 | buf->tail = n; |
facd885c DV |
277 | /* paired w/ acquire in flush_to_ldisc(); ensures |
278 | * flush_to_ldisc() sees buffer data. | |
279 | */ | |
280 | smp_store_release(&b->commit, b->used); | |
069f38b4 | 281 | /* paired w/ acquire in flush_to_ldisc(); ensures the |
62a0d8d7 PH |
282 | * latest commit value can be read before the head is |
283 | * advanced to the next buffer | |
284 | */ | |
069f38b4 | 285 | smp_store_release(&b->next, n); |
acc0f67f PH |
286 | } else if (change) |
287 | size = 0; | |
288 | else | |
e0495736 AC |
289 | size = left; |
290 | } | |
e0495736 AC |
291 | return size; |
292 | } | |
acc0f67f PH |
293 | |
294 | int tty_buffer_request_room(struct tty_port *port, size_t size) | |
295 | { | |
296 | return __tty_buffer_request_room(port, size, 0); | |
297 | } | |
e0495736 AC |
298 | EXPORT_SYMBOL_GPL(tty_buffer_request_room); |
299 | ||
300 | /** | |
2832fc11 | 301 | * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer |
2f693357 | 302 | * @port: tty port |
e0495736 | 303 | * @chars: characters |
2832fc11 | 304 | * @flag: flag value for each character |
e0495736 AC |
305 | * @size: size |
306 | * | |
307 | * Queue a series of bytes to the tty buffering. All the characters | |
ccc5ca8d | 308 | * passed are marked with the supplied flag. Returns the number added. |
e0495736 AC |
309 | */ |
310 | ||
2f693357 | 311 | int tty_insert_flip_string_fixed_flag(struct tty_port *port, |
2832fc11 | 312 | const unsigned char *chars, char flag, size_t size) |
e0495736 AC |
313 | { |
314 | int copied = 0; | |
315 | do { | |
d4bee0a6 | 316 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
acc0f67f PH |
317 | int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; |
318 | int space = __tty_buffer_request_room(port, goal, flags); | |
64325a3b | 319 | struct tty_buffer *tb = port->buf.tail; |
7391ee16 | 320 | if (unlikely(space == 0)) |
e0495736 | 321 | break; |
1fc359fc | 322 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
acc0f67f PH |
323 | if (~tb->flags & TTYB_NORMAL) |
324 | memset(flag_buf_ptr(tb, tb->used), flag, space); | |
e0495736 AC |
325 | tb->used += space; |
326 | copied += space; | |
327 | chars += space; | |
328 | /* There is a small chance that we need to split the data over | |
329 | several buffers. If this is the case we must loop */ | |
330 | } while (unlikely(size > copied)); | |
331 | return copied; | |
332 | } | |
2832fc11 | 333 | EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag); |
e0495736 AC |
334 | |
335 | /** | |
336 | * tty_insert_flip_string_flags - Add characters to the tty buffer | |
2f693357 | 337 | * @port: tty port |
e0495736 AC |
338 | * @chars: characters |
339 | * @flags: flag bytes | |
340 | * @size: size | |
341 | * | |
342 | * Queue a series of bytes to the tty buffering. For each character | |
343 | * the flags array indicates the status of the character. Returns the | |
344 | * number added. | |
e0495736 AC |
345 | */ |
346 | ||
2f693357 | 347 | int tty_insert_flip_string_flags(struct tty_port *port, |
e0495736 AC |
348 | const unsigned char *chars, const char *flags, size_t size) |
349 | { | |
350 | int copied = 0; | |
351 | do { | |
d4bee0a6 | 352 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
64325a3b IZ |
353 | int space = tty_buffer_request_room(port, goal); |
354 | struct tty_buffer *tb = port->buf.tail; | |
7391ee16 | 355 | if (unlikely(space == 0)) |
e0495736 | 356 | break; |
1fc359fc PH |
357 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
358 | memcpy(flag_buf_ptr(tb, tb->used), flags, space); | |
e0495736 AC |
359 | tb->used += space; |
360 | copied += space; | |
361 | chars += space; | |
362 | flags += space; | |
363 | /* There is a small chance that we need to split the data over | |
364 | several buffers. If this is the case we must loop */ | |
365 | } while (unlikely(size > copied)); | |
366 | return copied; | |
367 | } | |
368 | EXPORT_SYMBOL(tty_insert_flip_string_flags); | |
369 | ||
979990c6 AB |
370 | /** |
371 | * __tty_insert_flip_char - Add one character to the tty buffer | |
372 | * @port: tty port | |
373 | * @ch: character | |
374 | * @flag: flag byte | |
375 | * | |
376 | * Queue a single byte to the tty buffering, with an optional flag. | |
377 | * This is the slow path of tty_insert_flip_char. | |
378 | */ | |
379 | int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag) | |
380 | { | |
8a5a90a2 | 381 | struct tty_buffer *tb; |
979990c6 AB |
382 | int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; |
383 | ||
065ea0a7 | 384 | if (!__tty_buffer_request_room(port, 1, flags)) |
979990c6 AB |
385 | return 0; |
386 | ||
8a5a90a2 | 387 | tb = port->buf.tail; |
065ea0a7 AB |
388 | if (~tb->flags & TTYB_NORMAL) |
389 | *flag_buf_ptr(tb, tb->used) = flag; | |
979990c6 AB |
390 | *char_buf_ptr(tb, tb->used++) = ch; |
391 | ||
392 | return 1; | |
393 | } | |
394 | EXPORT_SYMBOL(__tty_insert_flip_char); | |
395 | ||
e0495736 AC |
396 | /** |
397 | * tty_schedule_flip - push characters to ldisc | |
6732c8bb | 398 | * @port: tty port to push from |
e0495736 AC |
399 | * |
400 | * Takes any pending buffers and transfers their ownership to the | |
401 | * ldisc side of the queue. It then schedules those characters for | |
402 | * processing by the line discipline. | |
e0495736 AC |
403 | */ |
404 | ||
6732c8bb | 405 | void tty_schedule_flip(struct tty_port *port) |
e0495736 | 406 | { |
6732c8bb | 407 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 408 | |
facd885c DV |
409 | /* paired w/ acquire in flush_to_ldisc(); ensures |
410 | * flush_to_ldisc() sees buffer data. | |
411 | */ | |
412 | smp_store_release(&buf->tail->commit, buf->tail->used); | |
e052c6d1 | 413 | queue_work(system_unbound_wq, &buf->work); |
e0495736 AC |
414 | } |
415 | EXPORT_SYMBOL(tty_schedule_flip); | |
416 | ||
417 | /** | |
418 | * tty_prepare_flip_string - make room for characters | |
2f693357 | 419 | * @port: tty port |
e0495736 AC |
420 | * @chars: return pointer for character write area |
421 | * @size: desired size | |
422 | * | |
423 | * Prepare a block of space in the buffer for data. Returns the length | |
424 | * available and buffer pointer to the space which is now allocated and | |
425 | * accounted for as ready for normal characters. This is used for drivers | |
426 | * that need their own block copy routines into the buffer. There is no | |
427 | * guarantee the buffer is a DMA target! | |
e0495736 AC |
428 | */ |
429 | ||
2f693357 | 430 | int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars, |
ecbbfd44 | 431 | size_t size) |
e0495736 | 432 | { |
acc0f67f | 433 | int space = __tty_buffer_request_room(port, size, TTYB_NORMAL); |
e0495736 | 434 | if (likely(space)) { |
64325a3b | 435 | struct tty_buffer *tb = port->buf.tail; |
1fc359fc | 436 | *chars = char_buf_ptr(tb, tb->used); |
acc0f67f PH |
437 | if (~tb->flags & TTYB_NORMAL) |
438 | memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space); | |
e0495736 AC |
439 | tb->used += space; |
440 | } | |
441 | return space; | |
442 | } | |
443 | EXPORT_SYMBOL_GPL(tty_prepare_flip_string); | |
444 | ||
8d082cd3 PH |
445 | /** |
446 | * tty_ldisc_receive_buf - forward data to line discipline | |
447 | * @ld: line discipline to process input | |
448 | * @p: char buffer | |
449 | * @f: TTY_* flags buffer | |
450 | * @count: number of bytes to process | |
451 | * | |
452 | * Callers other than flush_to_ldisc() need to exclude the kworker | |
453 | * from concurrent use of the line discipline, see paste_selection(). | |
454 | * | |
e7e51dcf | 455 | * Returns the number of bytes processed |
8d082cd3 | 456 | */ |
c92d781f | 457 | int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p, |
8d082cd3 PH |
458 | char *f, int count) |
459 | { | |
460 | if (ld->ops->receive_buf2) | |
461 | count = ld->ops->receive_buf2(ld->tty, p, f, count); | |
462 | else { | |
463 | count = min_t(int, count, ld->tty->receive_room); | |
464 | if (count && ld->ops->receive_buf) | |
465 | ld->ops->receive_buf(ld->tty, p, f, count); | |
466 | } | |
467 | return count; | |
468 | } | |
469 | EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf); | |
e0495736 | 470 | |
da261e7f | 471 | static int |
c3485ee0 | 472 | receive_buf(struct tty_port *port, struct tty_buffer *head, int count) |
da261e7f | 473 | { |
1fc359fc | 474 | unsigned char *p = char_buf_ptr(head, head->read); |
acc0f67f | 475 | char *f = NULL; |
c9a8e5fc | 476 | int n; |
acc0f67f PH |
477 | |
478 | if (~head->flags & TTYB_NORMAL) | |
479 | f = flag_buf_ptr(head, head->read); | |
da261e7f | 480 | |
c9a8e5fc LT |
481 | n = port->client_ops->receive_buf(port, p, f, count); |
482 | if (n > 0) | |
483 | memset(p, 0, n); | |
484 | return n; | |
da261e7f | 485 | } |
e0495736 AC |
486 | |
487 | /** | |
488 | * flush_to_ldisc | |
489 | * @work: tty structure passed from work queue. | |
490 | * | |
491 | * This routine is called out of the software interrupt to flush data | |
492 | * from the buffer chain to the line discipline. | |
493 | * | |
e9975fde PH |
494 | * The receive_buf method is single threaded for each tty instance. |
495 | * | |
a7c8d58c | 496 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 497 | * 'consumer' |
e0495736 AC |
498 | */ |
499 | ||
500 | static void flush_to_ldisc(struct work_struct *work) | |
501 | { | |
ecbbfd44 JS |
502 | struct tty_port *port = container_of(work, struct tty_port, buf.work); |
503 | struct tty_bufhead *buf = &port->buf; | |
e0495736 | 504 | |
a7c8d58c | 505 | mutex_lock(&buf->lock); |
45242006 | 506 | |
d7a68be4 PH |
507 | while (1) { |
508 | struct tty_buffer *head = buf->head; | |
62a0d8d7 | 509 | struct tty_buffer *next; |
d7a68be4 PH |
510 | int count; |
511 | ||
a7c8d58c PH |
512 | /* Ldisc or user is trying to gain exclusive access */ |
513 | if (atomic_read(&buf->priority)) | |
d7a68be4 PH |
514 | break; |
515 | ||
069f38b4 | 516 | /* paired w/ release in __tty_buffer_request_room(); |
62a0d8d7 PH |
517 | * ensures commit value read is not stale if the head |
518 | * is advancing to the next buffer | |
519 | */ | |
069f38b4 | 520 | next = smp_load_acquire(&head->next); |
facd885c DV |
521 | /* paired w/ release in __tty_buffer_request_room() or in |
522 | * tty_buffer_flush(); ensures we see the committed buffer data | |
523 | */ | |
524 | count = smp_load_acquire(&head->commit) - head->read; | |
d7a68be4 | 525 | if (!count) { |
0f40fbbc | 526 | if (next == NULL) |
da261e7f | 527 | break; |
62a0d8d7 | 528 | buf->head = next; |
d7a68be4 PH |
529 | tty_buffer_free(port, head); |
530 | continue; | |
e0495736 | 531 | } |
d7a68be4 | 532 | |
c3485ee0 | 533 | count = receive_buf(port, head, count); |
d7a68be4 PH |
534 | if (!count) |
535 | break; | |
af5554f9 | 536 | head->read += count; |
e0495736 | 537 | } |
45242006 | 538 | |
a7c8d58c | 539 | mutex_unlock(&buf->lock); |
e0495736 | 540 | |
e0495736 AC |
541 | } |
542 | ||
543 | /** | |
544 | * tty_flip_buffer_push - terminal | |
2e124b4a | 545 | * @port: tty port to push |
e0495736 | 546 | * |
a9c3f68f PH |
547 | * Queue a push of the terminal flip buffers to the line discipline. |
548 | * Can be called from IRQ/atomic context. | |
e0495736 AC |
549 | * |
550 | * In the event of the queue being busy for flipping the work will be | |
551 | * held off and retried later. | |
e0495736 AC |
552 | */ |
553 | ||
2e124b4a | 554 | void tty_flip_buffer_push(struct tty_port *port) |
e0495736 | 555 | { |
a9c3f68f | 556 | tty_schedule_flip(port); |
e0495736 AC |
557 | } |
558 | EXPORT_SYMBOL(tty_flip_buffer_push); | |
559 | ||
560 | /** | |
561 | * tty_buffer_init - prepare a tty buffer structure | |
fa441954 | 562 | * @port: tty port to initialise |
e0495736 AC |
563 | * |
564 | * Set up the initial state of the buffer management for a tty device. | |
565 | * Must be called before the other tty buffer functions are used. | |
e0495736 AC |
566 | */ |
567 | ||
ecbbfd44 | 568 | void tty_buffer_init(struct tty_port *port) |
e0495736 | 569 | { |
ecbbfd44 | 570 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 571 | |
a7c8d58c | 572 | mutex_init(&buf->lock); |
7391ee16 PH |
573 | tty_buffer_reset(&buf->sentinel, 0); |
574 | buf->head = &buf->sentinel; | |
575 | buf->tail = &buf->sentinel; | |
809850b7 | 576 | init_llist_head(&buf->free); |
5dda4ca5 | 577 | atomic_set(&buf->mem_used, 0); |
a7c8d58c | 578 | atomic_set(&buf->priority, 0); |
5cff39c6 | 579 | INIT_WORK(&buf->work, flush_to_ldisc); |
4d18e6ef | 580 | buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT; |
e0495736 | 581 | } |
4d18e6ef PH |
582 | |
583 | /** | |
584 | * tty_buffer_set_limit - change the tty buffer memory limit | |
585 | * @port: tty port to change | |
a776f10d | 586 | * @limit: memory limit to set |
4d18e6ef PH |
587 | * |
588 | * Change the tty buffer memory limit. | |
589 | * Must be called before the other tty buffer functions are used. | |
590 | */ | |
591 | ||
592 | int tty_buffer_set_limit(struct tty_port *port, int limit) | |
593 | { | |
594 | if (limit < MIN_TTYB_SIZE) | |
595 | return -EINVAL; | |
596 | port->buf.mem_limit = limit; | |
597 | return 0; | |
598 | } | |
599 | EXPORT_SYMBOL_GPL(tty_buffer_set_limit); | |
1d1d14da PH |
600 | |
601 | /* slave ptys can claim nested buffer lock when handling BRK and INTR */ | |
602 | void tty_buffer_set_lock_subclass(struct tty_port *port) | |
603 | { | |
604 | lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE); | |
605 | } | |
e176058f PH |
606 | |
607 | bool tty_buffer_restart_work(struct tty_port *port) | |
608 | { | |
609 | return queue_work(system_unbound_wq, &port->buf.work); | |
610 | } | |
611 | ||
612 | bool tty_buffer_cancel_work(struct tty_port *port) | |
613 | { | |
614 | return cancel_work_sync(&port->buf.work); | |
615 | } | |
0f40fbbc BB |
616 | |
617 | void tty_buffer_flush_work(struct tty_port *port) | |
618 | { | |
619 | flush_work(&port->buf.work); | |
620 | } |