Commit | Line | Data |
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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 | |
dadc1049 XT |
35 | * buffer is 256 byte aligned. See tty_buffer_find for the allocation |
36 | * logic this must match. | |
9114fe8c PH |
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 | ||
9a33fbf9 | 91 | unsigned int tty_buffer_space_avail(struct tty_port *port) |
7bfe0b71 | 92 | { |
5dda4ca5 | 93 | int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used); |
993c67b1 | 94 | |
7bfe0b71 PH |
95 | return max(space, 0); |
96 | } | |
c4a8dab5 | 97 | EXPORT_SYMBOL_GPL(tty_buffer_space_avail); |
7bfe0b71 | 98 | |
9dd5139f PH |
99 | static void tty_buffer_reset(struct tty_buffer *p, size_t size) |
100 | { | |
101 | p->used = 0; | |
102 | p->size = size; | |
103 | p->next = NULL; | |
104 | p->commit = 0; | |
105 | p->read = 0; | |
acc0f67f | 106 | p->flags = 0; |
9dd5139f PH |
107 | } |
108 | ||
e0495736 AC |
109 | /** |
110 | * tty_buffer_free_all - free buffers used by a tty | |
fa441954 | 111 | * @port: tty port to free from |
e0495736 AC |
112 | * |
113 | * Remove all the buffers pending on a tty whether queued with data | |
114 | * or in the free ring. Must be called when the tty is no longer in use | |
e0495736 AC |
115 | */ |
116 | ||
ecbbfd44 | 117 | void tty_buffer_free_all(struct tty_port *port) |
e0495736 | 118 | { |
ecbbfd44 | 119 | struct tty_bufhead *buf = &port->buf; |
809850b7 PH |
120 | struct tty_buffer *p, *next; |
121 | struct llist_node *llist; | |
feacbecb JS |
122 | unsigned int freed = 0; |
123 | int still_used; | |
5cff39c6 | 124 | |
2cf7b67e PH |
125 | while ((p = buf->head) != NULL) { |
126 | buf->head = p->next; | |
feacbecb | 127 | freed += p->size; |
7391ee16 PH |
128 | if (p->size > 0) |
129 | kfree(p); | |
e0495736 | 130 | } |
809850b7 PH |
131 | llist = llist_del_all(&buf->free); |
132 | llist_for_each_entry_safe(p, next, llist, free) | |
2cf7b67e | 133 | kfree(p); |
809850b7 | 134 | |
7391ee16 PH |
135 | tty_buffer_reset(&buf->sentinel, 0); |
136 | buf->head = &buf->sentinel; | |
137 | buf->tail = &buf->sentinel; | |
7bfe0b71 | 138 | |
feacbecb JS |
139 | still_used = atomic_xchg(&buf->mem_used, 0); |
140 | WARN(still_used != freed, "we still have not freed %d bytes!", | |
141 | still_used - freed); | |
e0495736 AC |
142 | } |
143 | ||
144 | /** | |
145 | * tty_buffer_alloc - allocate a tty buffer | |
fa441954 | 146 | * @port: tty port |
e0495736 AC |
147 | * @size: desired size (characters) |
148 | * | |
149 | * Allocate a new tty buffer to hold the desired number of characters. | |
11b9faa4 PH |
150 | * We round our buffers off in 256 character chunks to get better |
151 | * allocation behaviour. | |
e0495736 AC |
152 | * Return NULL if out of memory or the allocation would exceed the |
153 | * per device queue | |
e0495736 AC |
154 | */ |
155 | ||
ecbbfd44 | 156 | static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) |
e0495736 | 157 | { |
809850b7 | 158 | struct llist_node *free; |
e0495736 AC |
159 | struct tty_buffer *p; |
160 | ||
11b9faa4 PH |
161 | /* Round the buffer size out */ |
162 | size = __ALIGN_MASK(size, TTYB_ALIGN_MASK); | |
163 | ||
164 | if (size <= MIN_TTYB_SIZE) { | |
809850b7 PH |
165 | free = llist_del_first(&port->buf.free); |
166 | if (free) { | |
167 | p = llist_entry(free, struct tty_buffer, free); | |
11b9faa4 PH |
168 | goto found; |
169 | } | |
170 | } | |
171 | ||
172 | /* Should possibly check if this fails for the largest buffer we | |
80e3fce1 XT |
173 | * have queued and recycle that ? |
174 | */ | |
5dda4ca5 | 175 | if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit) |
e0495736 AC |
176 | return NULL; |
177 | p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); | |
178 | if (p == NULL) | |
179 | return NULL; | |
9dd5139f | 180 | |
11b9faa4 | 181 | found: |
9dd5139f | 182 | tty_buffer_reset(p, size); |
5dda4ca5 | 183 | atomic_add(size, &port->buf.mem_used); |
e0495736 AC |
184 | return p; |
185 | } | |
186 | ||
187 | /** | |
188 | * tty_buffer_free - free a tty buffer | |
fa441954 | 189 | * @port: tty port owning the buffer |
e0495736 AC |
190 | * @b: the buffer to free |
191 | * | |
192 | * Free a tty buffer, or add it to the free list according to our | |
193 | * internal strategy | |
e0495736 AC |
194 | */ |
195 | ||
ecbbfd44 | 196 | static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) |
e0495736 | 197 | { |
ecbbfd44 | 198 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 199 | |
e0495736 | 200 | /* Dumb strategy for now - should keep some stats */ |
5dda4ca5 | 201 | WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0); |
e0495736 | 202 | |
1cef50e3 | 203 | if (b->size > MIN_TTYB_SIZE) |
e0495736 | 204 | kfree(b); |
7391ee16 | 205 | else if (b->size > 0) |
809850b7 | 206 | llist_add(&b->free, &buf->free); |
e0495736 AC |
207 | } |
208 | ||
e0495736 AC |
209 | /** |
210 | * tty_buffer_flush - flush full tty buffers | |
211 | * @tty: tty to flush | |
86c80a8e | 212 | * @ld: optional ldisc ptr (must be referenced) |
e0495736 | 213 | * |
86c80a8e PH |
214 | * flush all the buffers containing receive data. If ld != NULL, |
215 | * flush the ldisc input buffer. | |
e0495736 | 216 | * |
a7c8d58c | 217 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 218 | * 'consumer' |
e0495736 AC |
219 | */ |
220 | ||
86c80a8e | 221 | void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld) |
e0495736 | 222 | { |
2fc20661 | 223 | struct tty_port *port = tty->port; |
ecbbfd44 | 224 | struct tty_bufhead *buf = &port->buf; |
47aa658a | 225 | struct tty_buffer *next; |
e0495736 | 226 | |
a7c8d58c | 227 | atomic_inc(&buf->priority); |
e9975fde | 228 | |
a7c8d58c | 229 | mutex_lock(&buf->lock); |
9e6b7cd7 DV |
230 | /* paired w/ release in __tty_buffer_request_room; ensures there are |
231 | * no pending memory accesses to the freed buffer | |
232 | */ | |
233 | while ((next = smp_load_acquire(&buf->head->next)) != NULL) { | |
47aa658a PH |
234 | tty_buffer_free(port, buf->head); |
235 | buf->head = next; | |
236 | } | |
237 | buf->head->read = buf->head->commit; | |
86c80a8e PH |
238 | |
239 | if (ld && ld->ops->flush_buffer) | |
240 | ld->ops->flush_buffer(tty); | |
241 | ||
a7c8d58c PH |
242 | atomic_dec(&buf->priority); |
243 | mutex_unlock(&buf->lock); | |
e0495736 AC |
244 | } |
245 | ||
e0495736 | 246 | /** |
a1c0da88 | 247 | * __tty_buffer_request_room - grow tty buffer if needed |
fa441954 | 248 | * @port: tty port |
e0495736 | 249 | * @size: size desired |
acc0f67f | 250 | * @flags: buffer flags if new buffer allocated (default = 0) |
e0495736 AC |
251 | * |
252 | * Make at least size bytes of linear space available for the tty | |
253 | * buffer. If we fail return the size we managed to find. | |
acc0f67f PH |
254 | * |
255 | * Will change over to a new buffer if the current buffer is encoded as | |
256 | * TTY_NORMAL (so has no flags buffer) and the new buffer requires | |
257 | * a flags buffer. | |
e0495736 | 258 | */ |
acc0f67f PH |
259 | static int __tty_buffer_request_room(struct tty_port *port, size_t size, |
260 | int flags) | |
e0495736 | 261 | { |
ecbbfd44 | 262 | struct tty_bufhead *buf = &port->buf; |
e0495736 | 263 | struct tty_buffer *b, *n; |
acc0f67f | 264 | int left, change; |
e8437d7e | 265 | |
5cff39c6 | 266 | b = buf->tail; |
acc0f67f PH |
267 | if (b->flags & TTYB_NORMAL) |
268 | left = 2 * b->size - b->used; | |
269 | else | |
270 | left = b->size - b->used; | |
e0495736 | 271 | |
acc0f67f PH |
272 | change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL); |
273 | if (change || left < size) { | |
e0495736 | 274 | /* This is the slow path - looking for new buffers to use */ |
e16cb0a7 GKH |
275 | n = tty_buffer_alloc(port, size); |
276 | if (n != NULL) { | |
acc0f67f | 277 | n->flags = flags; |
5cff39c6 | 278 | buf->tail = n; |
facd885c DV |
279 | /* paired w/ acquire in flush_to_ldisc(); ensures |
280 | * flush_to_ldisc() sees buffer data. | |
281 | */ | |
282 | smp_store_release(&b->commit, b->used); | |
069f38b4 | 283 | /* paired w/ acquire in flush_to_ldisc(); ensures the |
62a0d8d7 PH |
284 | * latest commit value can be read before the head is |
285 | * advanced to the next buffer | |
286 | */ | |
069f38b4 | 287 | smp_store_release(&b->next, n); |
acc0f67f PH |
288 | } else if (change) |
289 | size = 0; | |
290 | else | |
e0495736 AC |
291 | size = left; |
292 | } | |
e0495736 AC |
293 | return size; |
294 | } | |
acc0f67f PH |
295 | |
296 | int tty_buffer_request_room(struct tty_port *port, size_t size) | |
297 | { | |
298 | return __tty_buffer_request_room(port, size, 0); | |
299 | } | |
e0495736 AC |
300 | EXPORT_SYMBOL_GPL(tty_buffer_request_room); |
301 | ||
302 | /** | |
2832fc11 | 303 | * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer |
2f693357 | 304 | * @port: tty port |
e0495736 | 305 | * @chars: characters |
2832fc11 | 306 | * @flag: flag value for each character |
e0495736 AC |
307 | * @size: size |
308 | * | |
309 | * Queue a series of bytes to the tty buffering. All the characters | |
ccc5ca8d | 310 | * passed are marked with the supplied flag. Returns the number added. |
e0495736 AC |
311 | */ |
312 | ||
2f693357 | 313 | int tty_insert_flip_string_fixed_flag(struct tty_port *port, |
2832fc11 | 314 | const unsigned char *chars, char flag, size_t size) |
e0495736 AC |
315 | { |
316 | int copied = 0; | |
993c67b1 | 317 | |
e0495736 | 318 | do { |
d4bee0a6 | 319 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
acc0f67f PH |
320 | int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; |
321 | int space = __tty_buffer_request_room(port, goal, flags); | |
64325a3b | 322 | struct tty_buffer *tb = port->buf.tail; |
993c67b1 | 323 | |
7391ee16 | 324 | if (unlikely(space == 0)) |
e0495736 | 325 | break; |
1fc359fc | 326 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
acc0f67f PH |
327 | if (~tb->flags & TTYB_NORMAL) |
328 | memset(flag_buf_ptr(tb, tb->used), flag, space); | |
e0495736 AC |
329 | tb->used += space; |
330 | copied += space; | |
331 | chars += space; | |
332 | /* There is a small chance that we need to split the data over | |
80e3fce1 XT |
333 | * several buffers. If this is the case we must loop. |
334 | */ | |
e0495736 AC |
335 | } while (unlikely(size > copied)); |
336 | return copied; | |
337 | } | |
2832fc11 | 338 | EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag); |
e0495736 AC |
339 | |
340 | /** | |
341 | * tty_insert_flip_string_flags - Add characters to the tty buffer | |
2f693357 | 342 | * @port: tty port |
e0495736 AC |
343 | * @chars: characters |
344 | * @flags: flag bytes | |
345 | * @size: size | |
346 | * | |
347 | * Queue a series of bytes to the tty buffering. For each character | |
348 | * the flags array indicates the status of the character. Returns the | |
349 | * number added. | |
e0495736 AC |
350 | */ |
351 | ||
2f693357 | 352 | int tty_insert_flip_string_flags(struct tty_port *port, |
e0495736 AC |
353 | const unsigned char *chars, const char *flags, size_t size) |
354 | { | |
355 | int copied = 0; | |
993c67b1 | 356 | |
e0495736 | 357 | do { |
d4bee0a6 | 358 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
64325a3b IZ |
359 | int space = tty_buffer_request_room(port, goal); |
360 | struct tty_buffer *tb = port->buf.tail; | |
993c67b1 | 361 | |
7391ee16 | 362 | if (unlikely(space == 0)) |
e0495736 | 363 | break; |
1fc359fc PH |
364 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
365 | memcpy(flag_buf_ptr(tb, tb->used), flags, space); | |
e0495736 AC |
366 | tb->used += space; |
367 | copied += space; | |
368 | chars += space; | |
369 | flags += space; | |
370 | /* There is a small chance that we need to split the data over | |
80e3fce1 XT |
371 | * several buffers. If this is the case we must loop. |
372 | */ | |
e0495736 AC |
373 | } while (unlikely(size > copied)); |
374 | return copied; | |
375 | } | |
376 | EXPORT_SYMBOL(tty_insert_flip_string_flags); | |
377 | ||
979990c6 AB |
378 | /** |
379 | * __tty_insert_flip_char - Add one character to the tty buffer | |
380 | * @port: tty port | |
381 | * @ch: character | |
382 | * @flag: flag byte | |
383 | * | |
384 | * Queue a single byte to the tty buffering, with an optional flag. | |
385 | * This is the slow path of tty_insert_flip_char. | |
386 | */ | |
387 | int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag) | |
388 | { | |
8a5a90a2 | 389 | struct tty_buffer *tb; |
979990c6 AB |
390 | int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; |
391 | ||
065ea0a7 | 392 | if (!__tty_buffer_request_room(port, 1, flags)) |
979990c6 AB |
393 | return 0; |
394 | ||
8a5a90a2 | 395 | tb = port->buf.tail; |
065ea0a7 AB |
396 | if (~tb->flags & TTYB_NORMAL) |
397 | *flag_buf_ptr(tb, tb->used) = flag; | |
979990c6 AB |
398 | *char_buf_ptr(tb, tb->used++) = ch; |
399 | ||
400 | return 1; | |
401 | } | |
402 | EXPORT_SYMBOL(__tty_insert_flip_char); | |
403 | ||
e0495736 AC |
404 | /** |
405 | * tty_schedule_flip - push characters to ldisc | |
6732c8bb | 406 | * @port: tty port to push from |
e0495736 AC |
407 | * |
408 | * Takes any pending buffers and transfers their ownership to the | |
409 | * ldisc side of the queue. It then schedules those characters for | |
410 | * processing by the line discipline. | |
e0495736 AC |
411 | */ |
412 | ||
6732c8bb | 413 | void tty_schedule_flip(struct tty_port *port) |
e0495736 | 414 | { |
6732c8bb | 415 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 416 | |
facd885c DV |
417 | /* paired w/ acquire in flush_to_ldisc(); ensures |
418 | * flush_to_ldisc() sees buffer data. | |
419 | */ | |
420 | smp_store_release(&buf->tail->commit, buf->tail->used); | |
e052c6d1 | 421 | queue_work(system_unbound_wq, &buf->work); |
e0495736 AC |
422 | } |
423 | EXPORT_SYMBOL(tty_schedule_flip); | |
424 | ||
425 | /** | |
426 | * tty_prepare_flip_string - make room for characters | |
2f693357 | 427 | * @port: tty port |
e0495736 AC |
428 | * @chars: return pointer for character write area |
429 | * @size: desired size | |
430 | * | |
431 | * Prepare a block of space in the buffer for data. Returns the length | |
432 | * available and buffer pointer to the space which is now allocated and | |
433 | * accounted for as ready for normal characters. This is used for drivers | |
434 | * that need their own block copy routines into the buffer. There is no | |
435 | * guarantee the buffer is a DMA target! | |
e0495736 AC |
436 | */ |
437 | ||
2f693357 | 438 | int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars, |
ecbbfd44 | 439 | size_t size) |
e0495736 | 440 | { |
acc0f67f | 441 | int space = __tty_buffer_request_room(port, size, TTYB_NORMAL); |
993c67b1 | 442 | |
e0495736 | 443 | if (likely(space)) { |
64325a3b | 444 | struct tty_buffer *tb = port->buf.tail; |
993c67b1 | 445 | |
1fc359fc | 446 | *chars = char_buf_ptr(tb, tb->used); |
acc0f67f PH |
447 | if (~tb->flags & TTYB_NORMAL) |
448 | memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space); | |
e0495736 AC |
449 | tb->used += space; |
450 | } | |
451 | return space; | |
452 | } | |
453 | EXPORT_SYMBOL_GPL(tty_prepare_flip_string); | |
454 | ||
8d082cd3 PH |
455 | /** |
456 | * tty_ldisc_receive_buf - forward data to line discipline | |
457 | * @ld: line discipline to process input | |
458 | * @p: char buffer | |
459 | * @f: TTY_* flags buffer | |
460 | * @count: number of bytes to process | |
461 | * | |
462 | * Callers other than flush_to_ldisc() need to exclude the kworker | |
463 | * from concurrent use of the line discipline, see paste_selection(). | |
464 | * | |
e7e51dcf | 465 | * Returns the number of bytes processed |
8d082cd3 | 466 | */ |
c92d781f | 467 | int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p, |
0f3dcf3b | 468 | const char *f, int count) |
8d082cd3 PH |
469 | { |
470 | if (ld->ops->receive_buf2) | |
471 | count = ld->ops->receive_buf2(ld->tty, p, f, count); | |
472 | else { | |
473 | count = min_t(int, count, ld->tty->receive_room); | |
474 | if (count && ld->ops->receive_buf) | |
475 | ld->ops->receive_buf(ld->tty, p, f, count); | |
476 | } | |
477 | return count; | |
478 | } | |
479 | EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf); | |
e0495736 | 480 | |
da261e7f | 481 | static int |
c3485ee0 | 482 | receive_buf(struct tty_port *port, struct tty_buffer *head, int count) |
da261e7f | 483 | { |
1fc359fc | 484 | unsigned char *p = char_buf_ptr(head, head->read); |
0f3dcf3b | 485 | const char *f = NULL; |
c9a8e5fc | 486 | int n; |
acc0f67f PH |
487 | |
488 | if (~head->flags & TTYB_NORMAL) | |
489 | f = flag_buf_ptr(head, head->read); | |
da261e7f | 490 | |
c9a8e5fc LT |
491 | n = port->client_ops->receive_buf(port, p, f, count); |
492 | if (n > 0) | |
493 | memset(p, 0, n); | |
494 | return n; | |
da261e7f | 495 | } |
e0495736 AC |
496 | |
497 | /** | |
498 | * flush_to_ldisc | |
499 | * @work: tty structure passed from work queue. | |
500 | * | |
501 | * This routine is called out of the software interrupt to flush data | |
502 | * from the buffer chain to the line discipline. | |
503 | * | |
e9975fde PH |
504 | * The receive_buf method is single threaded for each tty instance. |
505 | * | |
a7c8d58c | 506 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 507 | * 'consumer' |
e0495736 AC |
508 | */ |
509 | ||
510 | static void flush_to_ldisc(struct work_struct *work) | |
511 | { | |
ecbbfd44 JS |
512 | struct tty_port *port = container_of(work, struct tty_port, buf.work); |
513 | struct tty_bufhead *buf = &port->buf; | |
e0495736 | 514 | |
a7c8d58c | 515 | mutex_lock(&buf->lock); |
45242006 | 516 | |
d7a68be4 PH |
517 | while (1) { |
518 | struct tty_buffer *head = buf->head; | |
62a0d8d7 | 519 | struct tty_buffer *next; |
d7a68be4 PH |
520 | int count; |
521 | ||
a7c8d58c PH |
522 | /* Ldisc or user is trying to gain exclusive access */ |
523 | if (atomic_read(&buf->priority)) | |
d7a68be4 PH |
524 | break; |
525 | ||
069f38b4 | 526 | /* paired w/ release in __tty_buffer_request_room(); |
62a0d8d7 PH |
527 | * ensures commit value read is not stale if the head |
528 | * is advancing to the next buffer | |
529 | */ | |
069f38b4 | 530 | next = smp_load_acquire(&head->next); |
facd885c DV |
531 | /* paired w/ release in __tty_buffer_request_room() or in |
532 | * tty_buffer_flush(); ensures we see the committed buffer data | |
533 | */ | |
534 | count = smp_load_acquire(&head->commit) - head->read; | |
d7a68be4 | 535 | if (!count) { |
0f40fbbc | 536 | if (next == NULL) |
da261e7f | 537 | break; |
62a0d8d7 | 538 | buf->head = next; |
d7a68be4 PH |
539 | tty_buffer_free(port, head); |
540 | continue; | |
e0495736 | 541 | } |
d7a68be4 | 542 | |
c3485ee0 | 543 | count = receive_buf(port, head, count); |
d7a68be4 PH |
544 | if (!count) |
545 | break; | |
af5554f9 | 546 | head->read += count; |
e0495736 | 547 | } |
45242006 | 548 | |
a7c8d58c | 549 | mutex_unlock(&buf->lock); |
e0495736 | 550 | |
e0495736 AC |
551 | } |
552 | ||
553 | /** | |
554 | * tty_flip_buffer_push - terminal | |
2e124b4a | 555 | * @port: tty port to push |
e0495736 | 556 | * |
a9c3f68f PH |
557 | * Queue a push of the terminal flip buffers to the line discipline. |
558 | * Can be called from IRQ/atomic context. | |
e0495736 AC |
559 | * |
560 | * In the event of the queue being busy for flipping the work will be | |
561 | * held off and retried later. | |
e0495736 AC |
562 | */ |
563 | ||
2e124b4a | 564 | void tty_flip_buffer_push(struct tty_port *port) |
e0495736 | 565 | { |
a9c3f68f | 566 | tty_schedule_flip(port); |
e0495736 AC |
567 | } |
568 | EXPORT_SYMBOL(tty_flip_buffer_push); | |
569 | ||
570 | /** | |
571 | * tty_buffer_init - prepare a tty buffer structure | |
fa441954 | 572 | * @port: tty port to initialise |
e0495736 AC |
573 | * |
574 | * Set up the initial state of the buffer management for a tty device. | |
575 | * Must be called before the other tty buffer functions are used. | |
e0495736 AC |
576 | */ |
577 | ||
ecbbfd44 | 578 | void tty_buffer_init(struct tty_port *port) |
e0495736 | 579 | { |
ecbbfd44 | 580 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 581 | |
a7c8d58c | 582 | mutex_init(&buf->lock); |
7391ee16 PH |
583 | tty_buffer_reset(&buf->sentinel, 0); |
584 | buf->head = &buf->sentinel; | |
585 | buf->tail = &buf->sentinel; | |
809850b7 | 586 | init_llist_head(&buf->free); |
5dda4ca5 | 587 | atomic_set(&buf->mem_used, 0); |
a7c8d58c | 588 | atomic_set(&buf->priority, 0); |
5cff39c6 | 589 | INIT_WORK(&buf->work, flush_to_ldisc); |
4d18e6ef | 590 | buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT; |
e0495736 | 591 | } |
4d18e6ef PH |
592 | |
593 | /** | |
594 | * tty_buffer_set_limit - change the tty buffer memory limit | |
595 | * @port: tty port to change | |
a776f10d | 596 | * @limit: memory limit to set |
4d18e6ef PH |
597 | * |
598 | * Change the tty buffer memory limit. | |
599 | * Must be called before the other tty buffer functions are used. | |
600 | */ | |
601 | ||
602 | int tty_buffer_set_limit(struct tty_port *port, int limit) | |
603 | { | |
604 | if (limit < MIN_TTYB_SIZE) | |
605 | return -EINVAL; | |
606 | port->buf.mem_limit = limit; | |
607 | return 0; | |
608 | } | |
609 | EXPORT_SYMBOL_GPL(tty_buffer_set_limit); | |
1d1d14da PH |
610 | |
611 | /* slave ptys can claim nested buffer lock when handling BRK and INTR */ | |
612 | void tty_buffer_set_lock_subclass(struct tty_port *port) | |
613 | { | |
614 | lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE); | |
615 | } | |
e176058f PH |
616 | |
617 | bool tty_buffer_restart_work(struct tty_port *port) | |
618 | { | |
619 | return queue_work(system_unbound_wq, &port->buf.work); | |
620 | } | |
621 | ||
622 | bool tty_buffer_cancel_work(struct tty_port *port) | |
623 | { | |
624 | return cancel_work_sync(&port->buf.work); | |
625 | } | |
0f40fbbc BB |
626 | |
627 | void tty_buffer_flush_work(struct tty_port *port) | |
628 | { | |
629 | flush_work(&port->buf.work); | |
630 | } |