ring_buffer.c 52 KB

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  1. /*
  2. * Generic ring buffer
  3. *
  4. * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
  5. */
  6. #include <linux/ring_buffer.h>
  7. #include <linux/spinlock.h>
  8. #include <linux/debugfs.h>
  9. #include <linux/uaccess.h>
  10. #include <linux/module.h>
  11. #include <linux/percpu.h>
  12. #include <linux/mutex.h>
  13. #include <linux/sched.h> /* used for sched_clock() (for now) */
  14. #include <linux/init.h>
  15. #include <linux/hash.h>
  16. #include <linux/list.h>
  17. #include <linux/fs.h>
  18. #include "trace.h"
  19. /* Global flag to disable all recording to ring buffers */
  20. static int ring_buffers_off __read_mostly;
  21. /**
  22. * tracing_on - enable all tracing buffers
  23. *
  24. * This function enables all tracing buffers that may have been
  25. * disabled with tracing_off.
  26. */
  27. void tracing_on(void)
  28. {
  29. ring_buffers_off = 0;
  30. }
  31. /**
  32. * tracing_off - turn off all tracing buffers
  33. *
  34. * This function stops all tracing buffers from recording data.
  35. * It does not disable any overhead the tracers themselves may
  36. * be causing. This function simply causes all recording to
  37. * the ring buffers to fail.
  38. */
  39. void tracing_off(void)
  40. {
  41. ring_buffers_off = 1;
  42. }
  43. /* Up this if you want to test the TIME_EXTENTS and normalization */
  44. #define DEBUG_SHIFT 0
  45. /* FIXME!!! */
  46. u64 ring_buffer_time_stamp(int cpu)
  47. {
  48. u64 time;
  49. preempt_disable_notrace();
  50. /* shift to debug/test normalization and TIME_EXTENTS */
  51. time = sched_clock() << DEBUG_SHIFT;
  52. preempt_enable_notrace();
  53. return time;
  54. }
  55. void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
  56. {
  57. /* Just stupid testing the normalize function and deltas */
  58. *ts >>= DEBUG_SHIFT;
  59. }
  60. #define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
  61. #define RB_ALIGNMENT_SHIFT 2
  62. #define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
  63. #define RB_MAX_SMALL_DATA 28
  64. enum {
  65. RB_LEN_TIME_EXTEND = 8,
  66. RB_LEN_TIME_STAMP = 16,
  67. };
  68. /* inline for ring buffer fast paths */
  69. static inline unsigned
  70. rb_event_length(struct ring_buffer_event *event)
  71. {
  72. unsigned length;
  73. switch (event->type) {
  74. case RINGBUF_TYPE_PADDING:
  75. /* undefined */
  76. return -1;
  77. case RINGBUF_TYPE_TIME_EXTEND:
  78. return RB_LEN_TIME_EXTEND;
  79. case RINGBUF_TYPE_TIME_STAMP:
  80. return RB_LEN_TIME_STAMP;
  81. case RINGBUF_TYPE_DATA:
  82. if (event->len)
  83. length = event->len << RB_ALIGNMENT_SHIFT;
  84. else
  85. length = event->array[0];
  86. return length + RB_EVNT_HDR_SIZE;
  87. default:
  88. BUG();
  89. }
  90. /* not hit */
  91. return 0;
  92. }
  93. /**
  94. * ring_buffer_event_length - return the length of the event
  95. * @event: the event to get the length of
  96. */
  97. unsigned ring_buffer_event_length(struct ring_buffer_event *event)
  98. {
  99. return rb_event_length(event);
  100. }
  101. /* inline for ring buffer fast paths */
  102. static inline void *
  103. rb_event_data(struct ring_buffer_event *event)
  104. {
  105. BUG_ON(event->type != RINGBUF_TYPE_DATA);
  106. /* If length is in len field, then array[0] has the data */
  107. if (event->len)
  108. return (void *)&event->array[0];
  109. /* Otherwise length is in array[0] and array[1] has the data */
  110. return (void *)&event->array[1];
  111. }
  112. /**
  113. * ring_buffer_event_data - return the data of the event
  114. * @event: the event to get the data from
  115. */
  116. void *ring_buffer_event_data(struct ring_buffer_event *event)
  117. {
  118. return rb_event_data(event);
  119. }
  120. #define for_each_buffer_cpu(buffer, cpu) \
  121. for_each_cpu_mask(cpu, buffer->cpumask)
  122. #define TS_SHIFT 27
  123. #define TS_MASK ((1ULL << TS_SHIFT) - 1)
  124. #define TS_DELTA_TEST (~TS_MASK)
  125. /*
  126. * This hack stolen from mm/slob.c.
  127. * We can store per page timing information in the page frame of the page.
  128. * Thanks to Peter Zijlstra for suggesting this idea.
  129. */
  130. struct buffer_page {
  131. u64 time_stamp; /* page time stamp */
  132. local_t write; /* index for next write */
  133. local_t commit; /* write commited index */
  134. unsigned read; /* index for next read */
  135. struct list_head list; /* list of free pages */
  136. void *page; /* Actual data page */
  137. };
  138. /*
  139. * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
  140. * this issue out.
  141. */
  142. static inline void free_buffer_page(struct buffer_page *bpage)
  143. {
  144. if (bpage->page)
  145. free_page((unsigned long)bpage->page);
  146. kfree(bpage);
  147. }
  148. /*
  149. * We need to fit the time_stamp delta into 27 bits.
  150. */
  151. static inline int test_time_stamp(u64 delta)
  152. {
  153. if (delta & TS_DELTA_TEST)
  154. return 1;
  155. return 0;
  156. }
  157. #define BUF_PAGE_SIZE PAGE_SIZE
  158. /*
  159. * head_page == tail_page && head == tail then buffer is empty.
  160. */
  161. struct ring_buffer_per_cpu {
  162. int cpu;
  163. struct ring_buffer *buffer;
  164. spinlock_t lock;
  165. struct lock_class_key lock_key;
  166. struct list_head pages;
  167. struct buffer_page *head_page; /* read from head */
  168. struct buffer_page *tail_page; /* write to tail */
  169. struct buffer_page *commit_page; /* commited pages */
  170. struct buffer_page *reader_page;
  171. unsigned long overrun;
  172. unsigned long entries;
  173. u64 write_stamp;
  174. u64 read_stamp;
  175. atomic_t record_disabled;
  176. };
  177. struct ring_buffer {
  178. unsigned long size;
  179. unsigned pages;
  180. unsigned flags;
  181. int cpus;
  182. cpumask_t cpumask;
  183. atomic_t record_disabled;
  184. struct mutex mutex;
  185. struct ring_buffer_per_cpu **buffers;
  186. };
  187. struct ring_buffer_iter {
  188. struct ring_buffer_per_cpu *cpu_buffer;
  189. unsigned long head;
  190. struct buffer_page *head_page;
  191. u64 read_stamp;
  192. };
  193. #define RB_WARN_ON(buffer, cond) \
  194. do { \
  195. if (unlikely(cond)) { \
  196. atomic_inc(&buffer->record_disabled); \
  197. WARN_ON(1); \
  198. } \
  199. } while (0)
  200. #define RB_WARN_ON_RET(buffer, cond) \
  201. do { \
  202. if (unlikely(cond)) { \
  203. atomic_inc(&buffer->record_disabled); \
  204. WARN_ON(1); \
  205. return -1; \
  206. } \
  207. } while (0)
  208. #define RB_WARN_ON_ONCE(buffer, cond) \
  209. do { \
  210. static int once; \
  211. if (unlikely(cond) && !once) { \
  212. once++; \
  213. atomic_inc(&buffer->record_disabled); \
  214. WARN_ON(1); \
  215. } \
  216. } while (0)
  217. /**
  218. * check_pages - integrity check of buffer pages
  219. * @cpu_buffer: CPU buffer with pages to test
  220. *
  221. * As a safty measure we check to make sure the data pages have not
  222. * been corrupted.
  223. */
  224. static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
  225. {
  226. struct list_head *head = &cpu_buffer->pages;
  227. struct buffer_page *page, *tmp;
  228. RB_WARN_ON_RET(cpu_buffer, head->next->prev != head);
  229. RB_WARN_ON_RET(cpu_buffer, head->prev->next != head);
  230. list_for_each_entry_safe(page, tmp, head, list) {
  231. RB_WARN_ON_RET(cpu_buffer,
  232. page->list.next->prev != &page->list);
  233. RB_WARN_ON_RET(cpu_buffer,
  234. page->list.prev->next != &page->list);
  235. }
  236. return 0;
  237. }
  238. static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
  239. unsigned nr_pages)
  240. {
  241. struct list_head *head = &cpu_buffer->pages;
  242. struct buffer_page *page, *tmp;
  243. unsigned long addr;
  244. LIST_HEAD(pages);
  245. unsigned i;
  246. for (i = 0; i < nr_pages; i++) {
  247. page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
  248. GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
  249. if (!page)
  250. goto free_pages;
  251. list_add(&page->list, &pages);
  252. addr = __get_free_page(GFP_KERNEL);
  253. if (!addr)
  254. goto free_pages;
  255. page->page = (void *)addr;
  256. }
  257. list_splice(&pages, head);
  258. rb_check_pages(cpu_buffer);
  259. return 0;
  260. free_pages:
  261. list_for_each_entry_safe(page, tmp, &pages, list) {
  262. list_del_init(&page->list);
  263. free_buffer_page(page);
  264. }
  265. return -ENOMEM;
  266. }
  267. static struct ring_buffer_per_cpu *
  268. rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
  269. {
  270. struct ring_buffer_per_cpu *cpu_buffer;
  271. struct buffer_page *page;
  272. unsigned long addr;
  273. int ret;
  274. cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
  275. GFP_KERNEL, cpu_to_node(cpu));
  276. if (!cpu_buffer)
  277. return NULL;
  278. cpu_buffer->cpu = cpu;
  279. cpu_buffer->buffer = buffer;
  280. spin_lock_init(&cpu_buffer->lock);
  281. INIT_LIST_HEAD(&cpu_buffer->pages);
  282. page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
  283. GFP_KERNEL, cpu_to_node(cpu));
  284. if (!page)
  285. goto fail_free_buffer;
  286. cpu_buffer->reader_page = page;
  287. addr = __get_free_page(GFP_KERNEL);
  288. if (!addr)
  289. goto fail_free_reader;
  290. page->page = (void *)addr;
  291. INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
  292. ret = rb_allocate_pages(cpu_buffer, buffer->pages);
  293. if (ret < 0)
  294. goto fail_free_reader;
  295. cpu_buffer->head_page
  296. = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
  297. cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
  298. return cpu_buffer;
  299. fail_free_reader:
  300. free_buffer_page(cpu_buffer->reader_page);
  301. fail_free_buffer:
  302. kfree(cpu_buffer);
  303. return NULL;
  304. }
  305. static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
  306. {
  307. struct list_head *head = &cpu_buffer->pages;
  308. struct buffer_page *page, *tmp;
  309. list_del_init(&cpu_buffer->reader_page->list);
  310. free_buffer_page(cpu_buffer->reader_page);
  311. list_for_each_entry_safe(page, tmp, head, list) {
  312. list_del_init(&page->list);
  313. free_buffer_page(page);
  314. }
  315. kfree(cpu_buffer);
  316. }
  317. /*
  318. * Causes compile errors if the struct buffer_page gets bigger
  319. * than the struct page.
  320. */
  321. extern int ring_buffer_page_too_big(void);
  322. /**
  323. * ring_buffer_alloc - allocate a new ring_buffer
  324. * @size: the size in bytes that is needed.
  325. * @flags: attributes to set for the ring buffer.
  326. *
  327. * Currently the only flag that is available is the RB_FL_OVERWRITE
  328. * flag. This flag means that the buffer will overwrite old data
  329. * when the buffer wraps. If this flag is not set, the buffer will
  330. * drop data when the tail hits the head.
  331. */
  332. struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
  333. {
  334. struct ring_buffer *buffer;
  335. int bsize;
  336. int cpu;
  337. /* Paranoid! Optimizes out when all is well */
  338. if (sizeof(struct buffer_page) > sizeof(struct page))
  339. ring_buffer_page_too_big();
  340. /* keep it in its own cache line */
  341. buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
  342. GFP_KERNEL);
  343. if (!buffer)
  344. return NULL;
  345. buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
  346. buffer->flags = flags;
  347. /* need at least two pages */
  348. if (buffer->pages == 1)
  349. buffer->pages++;
  350. buffer->cpumask = cpu_possible_map;
  351. buffer->cpus = nr_cpu_ids;
  352. bsize = sizeof(void *) * nr_cpu_ids;
  353. buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
  354. GFP_KERNEL);
  355. if (!buffer->buffers)
  356. goto fail_free_buffer;
  357. for_each_buffer_cpu(buffer, cpu) {
  358. buffer->buffers[cpu] =
  359. rb_allocate_cpu_buffer(buffer, cpu);
  360. if (!buffer->buffers[cpu])
  361. goto fail_free_buffers;
  362. }
  363. mutex_init(&buffer->mutex);
  364. return buffer;
  365. fail_free_buffers:
  366. for_each_buffer_cpu(buffer, cpu) {
  367. if (buffer->buffers[cpu])
  368. rb_free_cpu_buffer(buffer->buffers[cpu]);
  369. }
  370. kfree(buffer->buffers);
  371. fail_free_buffer:
  372. kfree(buffer);
  373. return NULL;
  374. }
  375. /**
  376. * ring_buffer_free - free a ring buffer.
  377. * @buffer: the buffer to free.
  378. */
  379. void
  380. ring_buffer_free(struct ring_buffer *buffer)
  381. {
  382. int cpu;
  383. for_each_buffer_cpu(buffer, cpu)
  384. rb_free_cpu_buffer(buffer->buffers[cpu]);
  385. kfree(buffer);
  386. }
  387. static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
  388. static void
  389. rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
  390. {
  391. struct buffer_page *page;
  392. struct list_head *p;
  393. unsigned i;
  394. atomic_inc(&cpu_buffer->record_disabled);
  395. synchronize_sched();
  396. for (i = 0; i < nr_pages; i++) {
  397. BUG_ON(list_empty(&cpu_buffer->pages));
  398. p = cpu_buffer->pages.next;
  399. page = list_entry(p, struct buffer_page, list);
  400. list_del_init(&page->list);
  401. free_buffer_page(page);
  402. }
  403. BUG_ON(list_empty(&cpu_buffer->pages));
  404. rb_reset_cpu(cpu_buffer);
  405. rb_check_pages(cpu_buffer);
  406. atomic_dec(&cpu_buffer->record_disabled);
  407. }
  408. static void
  409. rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
  410. struct list_head *pages, unsigned nr_pages)
  411. {
  412. struct buffer_page *page;
  413. struct list_head *p;
  414. unsigned i;
  415. atomic_inc(&cpu_buffer->record_disabled);
  416. synchronize_sched();
  417. for (i = 0; i < nr_pages; i++) {
  418. BUG_ON(list_empty(pages));
  419. p = pages->next;
  420. page = list_entry(p, struct buffer_page, list);
  421. list_del_init(&page->list);
  422. list_add_tail(&page->list, &cpu_buffer->pages);
  423. }
  424. rb_reset_cpu(cpu_buffer);
  425. rb_check_pages(cpu_buffer);
  426. atomic_dec(&cpu_buffer->record_disabled);
  427. }
  428. /**
  429. * ring_buffer_resize - resize the ring buffer
  430. * @buffer: the buffer to resize.
  431. * @size: the new size.
  432. *
  433. * The tracer is responsible for making sure that the buffer is
  434. * not being used while changing the size.
  435. * Note: We may be able to change the above requirement by using
  436. * RCU synchronizations.
  437. *
  438. * Minimum size is 2 * BUF_PAGE_SIZE.
  439. *
  440. * Returns -1 on failure.
  441. */
  442. int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
  443. {
  444. struct ring_buffer_per_cpu *cpu_buffer;
  445. unsigned nr_pages, rm_pages, new_pages;
  446. struct buffer_page *page, *tmp;
  447. unsigned long buffer_size;
  448. unsigned long addr;
  449. LIST_HEAD(pages);
  450. int i, cpu;
  451. size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
  452. size *= BUF_PAGE_SIZE;
  453. buffer_size = buffer->pages * BUF_PAGE_SIZE;
  454. /* we need a minimum of two pages */
  455. if (size < BUF_PAGE_SIZE * 2)
  456. size = BUF_PAGE_SIZE * 2;
  457. if (size == buffer_size)
  458. return size;
  459. mutex_lock(&buffer->mutex);
  460. nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
  461. if (size < buffer_size) {
  462. /* easy case, just free pages */
  463. BUG_ON(nr_pages >= buffer->pages);
  464. rm_pages = buffer->pages - nr_pages;
  465. for_each_buffer_cpu(buffer, cpu) {
  466. cpu_buffer = buffer->buffers[cpu];
  467. rb_remove_pages(cpu_buffer, rm_pages);
  468. }
  469. goto out;
  470. }
  471. /*
  472. * This is a bit more difficult. We only want to add pages
  473. * when we can allocate enough for all CPUs. We do this
  474. * by allocating all the pages and storing them on a local
  475. * link list. If we succeed in our allocation, then we
  476. * add these pages to the cpu_buffers. Otherwise we just free
  477. * them all and return -ENOMEM;
  478. */
  479. BUG_ON(nr_pages <= buffer->pages);
  480. new_pages = nr_pages - buffer->pages;
  481. for_each_buffer_cpu(buffer, cpu) {
  482. for (i = 0; i < new_pages; i++) {
  483. page = kzalloc_node(ALIGN(sizeof(*page),
  484. cache_line_size()),
  485. GFP_KERNEL, cpu_to_node(cpu));
  486. if (!page)
  487. goto free_pages;
  488. list_add(&page->list, &pages);
  489. addr = __get_free_page(GFP_KERNEL);
  490. if (!addr)
  491. goto free_pages;
  492. page->page = (void *)addr;
  493. }
  494. }
  495. for_each_buffer_cpu(buffer, cpu) {
  496. cpu_buffer = buffer->buffers[cpu];
  497. rb_insert_pages(cpu_buffer, &pages, new_pages);
  498. }
  499. BUG_ON(!list_empty(&pages));
  500. out:
  501. buffer->pages = nr_pages;
  502. mutex_unlock(&buffer->mutex);
  503. return size;
  504. free_pages:
  505. list_for_each_entry_safe(page, tmp, &pages, list) {
  506. list_del_init(&page->list);
  507. free_buffer_page(page);
  508. }
  509. return -ENOMEM;
  510. }
  511. static inline int rb_null_event(struct ring_buffer_event *event)
  512. {
  513. return event->type == RINGBUF_TYPE_PADDING;
  514. }
  515. static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
  516. {
  517. return page->page + index;
  518. }
  519. static inline struct ring_buffer_event *
  520. rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
  521. {
  522. return __rb_page_index(cpu_buffer->reader_page,
  523. cpu_buffer->reader_page->read);
  524. }
  525. static inline struct ring_buffer_event *
  526. rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
  527. {
  528. return __rb_page_index(cpu_buffer->head_page,
  529. cpu_buffer->head_page->read);
  530. }
  531. static inline struct ring_buffer_event *
  532. rb_iter_head_event(struct ring_buffer_iter *iter)
  533. {
  534. return __rb_page_index(iter->head_page, iter->head);
  535. }
  536. static inline unsigned rb_page_write(struct buffer_page *bpage)
  537. {
  538. return local_read(&bpage->write);
  539. }
  540. static inline unsigned rb_page_commit(struct buffer_page *bpage)
  541. {
  542. return local_read(&bpage->commit);
  543. }
  544. /* Size is determined by what has been commited */
  545. static inline unsigned rb_page_size(struct buffer_page *bpage)
  546. {
  547. return rb_page_commit(bpage);
  548. }
  549. static inline unsigned
  550. rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
  551. {
  552. return rb_page_commit(cpu_buffer->commit_page);
  553. }
  554. static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
  555. {
  556. return rb_page_commit(cpu_buffer->head_page);
  557. }
  558. /*
  559. * When the tail hits the head and the buffer is in overwrite mode,
  560. * the head jumps to the next page and all content on the previous
  561. * page is discarded. But before doing so, we update the overrun
  562. * variable of the buffer.
  563. */
  564. static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
  565. {
  566. struct ring_buffer_event *event;
  567. unsigned long head;
  568. for (head = 0; head < rb_head_size(cpu_buffer);
  569. head += rb_event_length(event)) {
  570. event = __rb_page_index(cpu_buffer->head_page, head);
  571. BUG_ON(rb_null_event(event));
  572. /* Only count data entries */
  573. if (event->type != RINGBUF_TYPE_DATA)
  574. continue;
  575. cpu_buffer->overrun++;
  576. cpu_buffer->entries--;
  577. }
  578. }
  579. static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
  580. struct buffer_page **page)
  581. {
  582. struct list_head *p = (*page)->list.next;
  583. if (p == &cpu_buffer->pages)
  584. p = p->next;
  585. *page = list_entry(p, struct buffer_page, list);
  586. }
  587. static inline unsigned
  588. rb_event_index(struct ring_buffer_event *event)
  589. {
  590. unsigned long addr = (unsigned long)event;
  591. return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
  592. }
  593. static inline int
  594. rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
  595. struct ring_buffer_event *event)
  596. {
  597. unsigned long addr = (unsigned long)event;
  598. unsigned long index;
  599. index = rb_event_index(event);
  600. addr &= PAGE_MASK;
  601. return cpu_buffer->commit_page->page == (void *)addr &&
  602. rb_commit_index(cpu_buffer) == index;
  603. }
  604. static inline void
  605. rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
  606. struct ring_buffer_event *event)
  607. {
  608. unsigned long addr = (unsigned long)event;
  609. unsigned long index;
  610. index = rb_event_index(event);
  611. addr &= PAGE_MASK;
  612. while (cpu_buffer->commit_page->page != (void *)addr) {
  613. RB_WARN_ON(cpu_buffer,
  614. cpu_buffer->commit_page == cpu_buffer->tail_page);
  615. cpu_buffer->commit_page->commit =
  616. cpu_buffer->commit_page->write;
  617. rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
  618. cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
  619. }
  620. /* Now set the commit to the event's index */
  621. local_set(&cpu_buffer->commit_page->commit, index);
  622. }
  623. static inline void
  624. rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
  625. {
  626. /*
  627. * We only race with interrupts and NMIs on this CPU.
  628. * If we own the commit event, then we can commit
  629. * all others that interrupted us, since the interruptions
  630. * are in stack format (they finish before they come
  631. * back to us). This allows us to do a simple loop to
  632. * assign the commit to the tail.
  633. */
  634. while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
  635. cpu_buffer->commit_page->commit =
  636. cpu_buffer->commit_page->write;
  637. rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
  638. cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
  639. /* add barrier to keep gcc from optimizing too much */
  640. barrier();
  641. }
  642. while (rb_commit_index(cpu_buffer) !=
  643. rb_page_write(cpu_buffer->commit_page)) {
  644. cpu_buffer->commit_page->commit =
  645. cpu_buffer->commit_page->write;
  646. barrier();
  647. }
  648. }
  649. static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
  650. {
  651. cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
  652. cpu_buffer->reader_page->read = 0;
  653. }
  654. static inline void rb_inc_iter(struct ring_buffer_iter *iter)
  655. {
  656. struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
  657. /*
  658. * The iterator could be on the reader page (it starts there).
  659. * But the head could have moved, since the reader was
  660. * found. Check for this case and assign the iterator
  661. * to the head page instead of next.
  662. */
  663. if (iter->head_page == cpu_buffer->reader_page)
  664. iter->head_page = cpu_buffer->head_page;
  665. else
  666. rb_inc_page(cpu_buffer, &iter->head_page);
  667. iter->read_stamp = iter->head_page->time_stamp;
  668. iter->head = 0;
  669. }
  670. /**
  671. * ring_buffer_update_event - update event type and data
  672. * @event: the even to update
  673. * @type: the type of event
  674. * @length: the size of the event field in the ring buffer
  675. *
  676. * Update the type and data fields of the event. The length
  677. * is the actual size that is written to the ring buffer,
  678. * and with this, we can determine what to place into the
  679. * data field.
  680. */
  681. static inline void
  682. rb_update_event(struct ring_buffer_event *event,
  683. unsigned type, unsigned length)
  684. {
  685. event->type = type;
  686. switch (type) {
  687. case RINGBUF_TYPE_PADDING:
  688. break;
  689. case RINGBUF_TYPE_TIME_EXTEND:
  690. event->len =
  691. (RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1))
  692. >> RB_ALIGNMENT_SHIFT;
  693. break;
  694. case RINGBUF_TYPE_TIME_STAMP:
  695. event->len =
  696. (RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1))
  697. >> RB_ALIGNMENT_SHIFT;
  698. break;
  699. case RINGBUF_TYPE_DATA:
  700. length -= RB_EVNT_HDR_SIZE;
  701. if (length > RB_MAX_SMALL_DATA) {
  702. event->len = 0;
  703. event->array[0] = length;
  704. } else
  705. event->len =
  706. (length + (RB_ALIGNMENT-1))
  707. >> RB_ALIGNMENT_SHIFT;
  708. break;
  709. default:
  710. BUG();
  711. }
  712. }
  713. static inline unsigned rb_calculate_event_length(unsigned length)
  714. {
  715. struct ring_buffer_event event; /* Used only for sizeof array */
  716. /* zero length can cause confusions */
  717. if (!length)
  718. length = 1;
  719. if (length > RB_MAX_SMALL_DATA)
  720. length += sizeof(event.array[0]);
  721. length += RB_EVNT_HDR_SIZE;
  722. length = ALIGN(length, RB_ALIGNMENT);
  723. return length;
  724. }
  725. static struct ring_buffer_event *
  726. __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
  727. unsigned type, unsigned long length, u64 *ts)
  728. {
  729. struct buffer_page *tail_page, *head_page, *reader_page;
  730. unsigned long tail, write;
  731. struct ring_buffer *buffer = cpu_buffer->buffer;
  732. struct ring_buffer_event *event;
  733. unsigned long flags;
  734. tail_page = cpu_buffer->tail_page;
  735. write = local_add_return(length, &tail_page->write);
  736. tail = write - length;
  737. /* See if we shot pass the end of this buffer page */
  738. if (write > BUF_PAGE_SIZE) {
  739. struct buffer_page *next_page = tail_page;
  740. spin_lock_irqsave(&cpu_buffer->lock, flags);
  741. rb_inc_page(cpu_buffer, &next_page);
  742. head_page = cpu_buffer->head_page;
  743. reader_page = cpu_buffer->reader_page;
  744. /* we grabbed the lock before incrementing */
  745. RB_WARN_ON(cpu_buffer, next_page == reader_page);
  746. /*
  747. * If for some reason, we had an interrupt storm that made
  748. * it all the way around the buffer, bail, and warn
  749. * about it.
  750. */
  751. if (unlikely(next_page == cpu_buffer->commit_page)) {
  752. WARN_ON_ONCE(1);
  753. goto out_unlock;
  754. }
  755. if (next_page == head_page) {
  756. if (!(buffer->flags & RB_FL_OVERWRITE)) {
  757. /* reset write */
  758. if (tail <= BUF_PAGE_SIZE)
  759. local_set(&tail_page->write, tail);
  760. goto out_unlock;
  761. }
  762. /* tail_page has not moved yet? */
  763. if (tail_page == cpu_buffer->tail_page) {
  764. /* count overflows */
  765. rb_update_overflow(cpu_buffer);
  766. rb_inc_page(cpu_buffer, &head_page);
  767. cpu_buffer->head_page = head_page;
  768. cpu_buffer->head_page->read = 0;
  769. }
  770. }
  771. /*
  772. * If the tail page is still the same as what we think
  773. * it is, then it is up to us to update the tail
  774. * pointer.
  775. */
  776. if (tail_page == cpu_buffer->tail_page) {
  777. local_set(&next_page->write, 0);
  778. local_set(&next_page->commit, 0);
  779. cpu_buffer->tail_page = next_page;
  780. /* reread the time stamp */
  781. *ts = ring_buffer_time_stamp(cpu_buffer->cpu);
  782. cpu_buffer->tail_page->time_stamp = *ts;
  783. }
  784. /*
  785. * The actual tail page has moved forward.
  786. */
  787. if (tail < BUF_PAGE_SIZE) {
  788. /* Mark the rest of the page with padding */
  789. event = __rb_page_index(tail_page, tail);
  790. event->type = RINGBUF_TYPE_PADDING;
  791. }
  792. if (tail <= BUF_PAGE_SIZE)
  793. /* Set the write back to the previous setting */
  794. local_set(&tail_page->write, tail);
  795. /*
  796. * If this was a commit entry that failed,
  797. * increment that too
  798. */
  799. if (tail_page == cpu_buffer->commit_page &&
  800. tail == rb_commit_index(cpu_buffer)) {
  801. rb_set_commit_to_write(cpu_buffer);
  802. }
  803. spin_unlock_irqrestore(&cpu_buffer->lock, flags);
  804. /* fail and let the caller try again */
  805. return ERR_PTR(-EAGAIN);
  806. }
  807. /* We reserved something on the buffer */
  808. BUG_ON(write > BUF_PAGE_SIZE);
  809. event = __rb_page_index(tail_page, tail);
  810. rb_update_event(event, type, length);
  811. /*
  812. * If this is a commit and the tail is zero, then update
  813. * this page's time stamp.
  814. */
  815. if (!tail && rb_is_commit(cpu_buffer, event))
  816. cpu_buffer->commit_page->time_stamp = *ts;
  817. return event;
  818. out_unlock:
  819. spin_unlock_irqrestore(&cpu_buffer->lock, flags);
  820. return NULL;
  821. }
  822. static int
  823. rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
  824. u64 *ts, u64 *delta)
  825. {
  826. struct ring_buffer_event *event;
  827. static int once;
  828. int ret;
  829. if (unlikely(*delta > (1ULL << 59) && !once++)) {
  830. printk(KERN_WARNING "Delta way too big! %llu"
  831. " ts=%llu write stamp = %llu\n",
  832. (unsigned long long)*delta,
  833. (unsigned long long)*ts,
  834. (unsigned long long)cpu_buffer->write_stamp);
  835. WARN_ON(1);
  836. }
  837. /*
  838. * The delta is too big, we to add a
  839. * new timestamp.
  840. */
  841. event = __rb_reserve_next(cpu_buffer,
  842. RINGBUF_TYPE_TIME_EXTEND,
  843. RB_LEN_TIME_EXTEND,
  844. ts);
  845. if (!event)
  846. return -EBUSY;
  847. if (PTR_ERR(event) == -EAGAIN)
  848. return -EAGAIN;
  849. /* Only a commited time event can update the write stamp */
  850. if (rb_is_commit(cpu_buffer, event)) {
  851. /*
  852. * If this is the first on the page, then we need to
  853. * update the page itself, and just put in a zero.
  854. */
  855. if (rb_event_index(event)) {
  856. event->time_delta = *delta & TS_MASK;
  857. event->array[0] = *delta >> TS_SHIFT;
  858. } else {
  859. cpu_buffer->commit_page->time_stamp = *ts;
  860. event->time_delta = 0;
  861. event->array[0] = 0;
  862. }
  863. cpu_buffer->write_stamp = *ts;
  864. /* let the caller know this was the commit */
  865. ret = 1;
  866. } else {
  867. /* Darn, this is just wasted space */
  868. event->time_delta = 0;
  869. event->array[0] = 0;
  870. ret = 0;
  871. }
  872. *delta = 0;
  873. return ret;
  874. }
  875. static struct ring_buffer_event *
  876. rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
  877. unsigned type, unsigned long length)
  878. {
  879. struct ring_buffer_event *event;
  880. u64 ts, delta;
  881. int commit = 0;
  882. int nr_loops = 0;
  883. again:
  884. /*
  885. * We allow for interrupts to reenter here and do a trace.
  886. * If one does, it will cause this original code to loop
  887. * back here. Even with heavy interrupts happening, this
  888. * should only happen a few times in a row. If this happens
  889. * 1000 times in a row, there must be either an interrupt
  890. * storm or we have something buggy.
  891. * Bail!
  892. */
  893. if (unlikely(++nr_loops > 1000)) {
  894. RB_WARN_ON(cpu_buffer, 1);
  895. return NULL;
  896. }
  897. ts = ring_buffer_time_stamp(cpu_buffer->cpu);
  898. /*
  899. * Only the first commit can update the timestamp.
  900. * Yes there is a race here. If an interrupt comes in
  901. * just after the conditional and it traces too, then it
  902. * will also check the deltas. More than one timestamp may
  903. * also be made. But only the entry that did the actual
  904. * commit will be something other than zero.
  905. */
  906. if (cpu_buffer->tail_page == cpu_buffer->commit_page &&
  907. rb_page_write(cpu_buffer->tail_page) ==
  908. rb_commit_index(cpu_buffer)) {
  909. delta = ts - cpu_buffer->write_stamp;
  910. /* make sure this delta is calculated here */
  911. barrier();
  912. /* Did the write stamp get updated already? */
  913. if (unlikely(ts < cpu_buffer->write_stamp))
  914. delta = 0;
  915. if (test_time_stamp(delta)) {
  916. commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
  917. if (commit == -EBUSY)
  918. return NULL;
  919. if (commit == -EAGAIN)
  920. goto again;
  921. RB_WARN_ON(cpu_buffer, commit < 0);
  922. }
  923. } else
  924. /* Non commits have zero deltas */
  925. delta = 0;
  926. event = __rb_reserve_next(cpu_buffer, type, length, &ts);
  927. if (PTR_ERR(event) == -EAGAIN)
  928. goto again;
  929. if (!event) {
  930. if (unlikely(commit))
  931. /*
  932. * Ouch! We needed a timestamp and it was commited. But
  933. * we didn't get our event reserved.
  934. */
  935. rb_set_commit_to_write(cpu_buffer);
  936. return NULL;
  937. }
  938. /*
  939. * If the timestamp was commited, make the commit our entry
  940. * now so that we will update it when needed.
  941. */
  942. if (commit)
  943. rb_set_commit_event(cpu_buffer, event);
  944. else if (!rb_is_commit(cpu_buffer, event))
  945. delta = 0;
  946. event->time_delta = delta;
  947. return event;
  948. }
  949. static DEFINE_PER_CPU(int, rb_need_resched);
  950. /**
  951. * ring_buffer_lock_reserve - reserve a part of the buffer
  952. * @buffer: the ring buffer to reserve from
  953. * @length: the length of the data to reserve (excluding event header)
  954. * @flags: a pointer to save the interrupt flags
  955. *
  956. * Returns a reseverd event on the ring buffer to copy directly to.
  957. * The user of this interface will need to get the body to write into
  958. * and can use the ring_buffer_event_data() interface.
  959. *
  960. * The length is the length of the data needed, not the event length
  961. * which also includes the event header.
  962. *
  963. * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
  964. * If NULL is returned, then nothing has been allocated or locked.
  965. */
  966. struct ring_buffer_event *
  967. ring_buffer_lock_reserve(struct ring_buffer *buffer,
  968. unsigned long length,
  969. unsigned long *flags)
  970. {
  971. struct ring_buffer_per_cpu *cpu_buffer;
  972. struct ring_buffer_event *event;
  973. int cpu, resched;
  974. if (ring_buffers_off)
  975. return NULL;
  976. if (atomic_read(&buffer->record_disabled))
  977. return NULL;
  978. /* If we are tracing schedule, we don't want to recurse */
  979. resched = need_resched();
  980. preempt_disable_notrace();
  981. cpu = raw_smp_processor_id();
  982. if (!cpu_isset(cpu, buffer->cpumask))
  983. goto out;
  984. cpu_buffer = buffer->buffers[cpu];
  985. if (atomic_read(&cpu_buffer->record_disabled))
  986. goto out;
  987. length = rb_calculate_event_length(length);
  988. if (length > BUF_PAGE_SIZE)
  989. goto out;
  990. event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length);
  991. if (!event)
  992. goto out;
  993. /*
  994. * Need to store resched state on this cpu.
  995. * Only the first needs to.
  996. */
  997. if (preempt_count() == 1)
  998. per_cpu(rb_need_resched, cpu) = resched;
  999. return event;
  1000. out:
  1001. if (resched)
  1002. preempt_enable_notrace();
  1003. else
  1004. preempt_enable_notrace();
  1005. return NULL;
  1006. }
  1007. static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
  1008. struct ring_buffer_event *event)
  1009. {
  1010. cpu_buffer->entries++;
  1011. /* Only process further if we own the commit */
  1012. if (!rb_is_commit(cpu_buffer, event))
  1013. return;
  1014. cpu_buffer->write_stamp += event->time_delta;
  1015. rb_set_commit_to_write(cpu_buffer);
  1016. }
  1017. /**
  1018. * ring_buffer_unlock_commit - commit a reserved
  1019. * @buffer: The buffer to commit to
  1020. * @event: The event pointer to commit.
  1021. * @flags: the interrupt flags received from ring_buffer_lock_reserve.
  1022. *
  1023. * This commits the data to the ring buffer, and releases any locks held.
  1024. *
  1025. * Must be paired with ring_buffer_lock_reserve.
  1026. */
  1027. int ring_buffer_unlock_commit(struct ring_buffer *buffer,
  1028. struct ring_buffer_event *event,
  1029. unsigned long flags)
  1030. {
  1031. struct ring_buffer_per_cpu *cpu_buffer;
  1032. int cpu = raw_smp_processor_id();
  1033. cpu_buffer = buffer->buffers[cpu];
  1034. rb_commit(cpu_buffer, event);
  1035. /*
  1036. * Only the last preempt count needs to restore preemption.
  1037. */
  1038. if (preempt_count() == 1) {
  1039. if (per_cpu(rb_need_resched, cpu))
  1040. preempt_enable_no_resched_notrace();
  1041. else
  1042. preempt_enable_notrace();
  1043. } else
  1044. preempt_enable_no_resched_notrace();
  1045. return 0;
  1046. }
  1047. /**
  1048. * ring_buffer_write - write data to the buffer without reserving
  1049. * @buffer: The ring buffer to write to.
  1050. * @length: The length of the data being written (excluding the event header)
  1051. * @data: The data to write to the buffer.
  1052. *
  1053. * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
  1054. * one function. If you already have the data to write to the buffer, it
  1055. * may be easier to simply call this function.
  1056. *
  1057. * Note, like ring_buffer_lock_reserve, the length is the length of the data
  1058. * and not the length of the event which would hold the header.
  1059. */
  1060. int ring_buffer_write(struct ring_buffer *buffer,
  1061. unsigned long length,
  1062. void *data)
  1063. {
  1064. struct ring_buffer_per_cpu *cpu_buffer;
  1065. struct ring_buffer_event *event;
  1066. unsigned long event_length;
  1067. void *body;
  1068. int ret = -EBUSY;
  1069. int cpu, resched;
  1070. if (ring_buffers_off)
  1071. return -EBUSY;
  1072. if (atomic_read(&buffer->record_disabled))
  1073. return -EBUSY;
  1074. resched = need_resched();
  1075. preempt_disable_notrace();
  1076. cpu = raw_smp_processor_id();
  1077. if (!cpu_isset(cpu, buffer->cpumask))
  1078. goto out;
  1079. cpu_buffer = buffer->buffers[cpu];
  1080. if (atomic_read(&cpu_buffer->record_disabled))
  1081. goto out;
  1082. event_length = rb_calculate_event_length(length);
  1083. event = rb_reserve_next_event(cpu_buffer,
  1084. RINGBUF_TYPE_DATA, event_length);
  1085. if (!event)
  1086. goto out;
  1087. body = rb_event_data(event);
  1088. memcpy(body, data, length);
  1089. rb_commit(cpu_buffer, event);
  1090. ret = 0;
  1091. out:
  1092. if (resched)
  1093. preempt_enable_no_resched_notrace();
  1094. else
  1095. preempt_enable_notrace();
  1096. return ret;
  1097. }
  1098. static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
  1099. {
  1100. struct buffer_page *reader = cpu_buffer->reader_page;
  1101. struct buffer_page *head = cpu_buffer->head_page;
  1102. struct buffer_page *commit = cpu_buffer->commit_page;
  1103. return reader->read == rb_page_commit(reader) &&
  1104. (commit == reader ||
  1105. (commit == head &&
  1106. head->read == rb_page_commit(commit)));
  1107. }
  1108. /**
  1109. * ring_buffer_record_disable - stop all writes into the buffer
  1110. * @buffer: The ring buffer to stop writes to.
  1111. *
  1112. * This prevents all writes to the buffer. Any attempt to write
  1113. * to the buffer after this will fail and return NULL.
  1114. *
  1115. * The caller should call synchronize_sched() after this.
  1116. */
  1117. void ring_buffer_record_disable(struct ring_buffer *buffer)
  1118. {
  1119. atomic_inc(&buffer->record_disabled);
  1120. }
  1121. /**
  1122. * ring_buffer_record_enable - enable writes to the buffer
  1123. * @buffer: The ring buffer to enable writes
  1124. *
  1125. * Note, multiple disables will need the same number of enables
  1126. * to truely enable the writing (much like preempt_disable).
  1127. */
  1128. void ring_buffer_record_enable(struct ring_buffer *buffer)
  1129. {
  1130. atomic_dec(&buffer->record_disabled);
  1131. }
  1132. /**
  1133. * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
  1134. * @buffer: The ring buffer to stop writes to.
  1135. * @cpu: The CPU buffer to stop
  1136. *
  1137. * This prevents all writes to the buffer. Any attempt to write
  1138. * to the buffer after this will fail and return NULL.
  1139. *
  1140. * The caller should call synchronize_sched() after this.
  1141. */
  1142. void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
  1143. {
  1144. struct ring_buffer_per_cpu *cpu_buffer;
  1145. if (!cpu_isset(cpu, buffer->cpumask))
  1146. return;
  1147. cpu_buffer = buffer->buffers[cpu];
  1148. atomic_inc(&cpu_buffer->record_disabled);
  1149. }
  1150. /**
  1151. * ring_buffer_record_enable_cpu - enable writes to the buffer
  1152. * @buffer: The ring buffer to enable writes
  1153. * @cpu: The CPU to enable.
  1154. *
  1155. * Note, multiple disables will need the same number of enables
  1156. * to truely enable the writing (much like preempt_disable).
  1157. */
  1158. void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
  1159. {
  1160. struct ring_buffer_per_cpu *cpu_buffer;
  1161. if (!cpu_isset(cpu, buffer->cpumask))
  1162. return;
  1163. cpu_buffer = buffer->buffers[cpu];
  1164. atomic_dec(&cpu_buffer->record_disabled);
  1165. }
  1166. /**
  1167. * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
  1168. * @buffer: The ring buffer
  1169. * @cpu: The per CPU buffer to get the entries from.
  1170. */
  1171. unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
  1172. {
  1173. struct ring_buffer_per_cpu *cpu_buffer;
  1174. if (!cpu_isset(cpu, buffer->cpumask))
  1175. return 0;
  1176. cpu_buffer = buffer->buffers[cpu];
  1177. return cpu_buffer->entries;
  1178. }
  1179. /**
  1180. * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
  1181. * @buffer: The ring buffer
  1182. * @cpu: The per CPU buffer to get the number of overruns from
  1183. */
  1184. unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
  1185. {
  1186. struct ring_buffer_per_cpu *cpu_buffer;
  1187. if (!cpu_isset(cpu, buffer->cpumask))
  1188. return 0;
  1189. cpu_buffer = buffer->buffers[cpu];
  1190. return cpu_buffer->overrun;
  1191. }
  1192. /**
  1193. * ring_buffer_entries - get the number of entries in a buffer
  1194. * @buffer: The ring buffer
  1195. *
  1196. * Returns the total number of entries in the ring buffer
  1197. * (all CPU entries)
  1198. */
  1199. unsigned long ring_buffer_entries(struct ring_buffer *buffer)
  1200. {
  1201. struct ring_buffer_per_cpu *cpu_buffer;
  1202. unsigned long entries = 0;
  1203. int cpu;
  1204. /* if you care about this being correct, lock the buffer */
  1205. for_each_buffer_cpu(buffer, cpu) {
  1206. cpu_buffer = buffer->buffers[cpu];
  1207. entries += cpu_buffer->entries;
  1208. }
  1209. return entries;
  1210. }
  1211. /**
  1212. * ring_buffer_overrun_cpu - get the number of overruns in buffer
  1213. * @buffer: The ring buffer
  1214. *
  1215. * Returns the total number of overruns in the ring buffer
  1216. * (all CPU entries)
  1217. */
  1218. unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
  1219. {
  1220. struct ring_buffer_per_cpu *cpu_buffer;
  1221. unsigned long overruns = 0;
  1222. int cpu;
  1223. /* if you care about this being correct, lock the buffer */
  1224. for_each_buffer_cpu(buffer, cpu) {
  1225. cpu_buffer = buffer->buffers[cpu];
  1226. overruns += cpu_buffer->overrun;
  1227. }
  1228. return overruns;
  1229. }
  1230. /**
  1231. * ring_buffer_iter_reset - reset an iterator
  1232. * @iter: The iterator to reset
  1233. *
  1234. * Resets the iterator, so that it will start from the beginning
  1235. * again.
  1236. */
  1237. void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
  1238. {
  1239. struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
  1240. /* Iterator usage is expected to have record disabled */
  1241. if (list_empty(&cpu_buffer->reader_page->list)) {
  1242. iter->head_page = cpu_buffer->head_page;
  1243. iter->head = cpu_buffer->head_page->read;
  1244. } else {
  1245. iter->head_page = cpu_buffer->reader_page;
  1246. iter->head = cpu_buffer->reader_page->read;
  1247. }
  1248. if (iter->head)
  1249. iter->read_stamp = cpu_buffer->read_stamp;
  1250. else
  1251. iter->read_stamp = iter->head_page->time_stamp;
  1252. }
  1253. /**
  1254. * ring_buffer_iter_empty - check if an iterator has no more to read
  1255. * @iter: The iterator to check
  1256. */
  1257. int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
  1258. {
  1259. struct ring_buffer_per_cpu *cpu_buffer;
  1260. cpu_buffer = iter->cpu_buffer;
  1261. return iter->head_page == cpu_buffer->commit_page &&
  1262. iter->head == rb_commit_index(cpu_buffer);
  1263. }
  1264. static void
  1265. rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
  1266. struct ring_buffer_event *event)
  1267. {
  1268. u64 delta;
  1269. switch (event->type) {
  1270. case RINGBUF_TYPE_PADDING:
  1271. return;
  1272. case RINGBUF_TYPE_TIME_EXTEND:
  1273. delta = event->array[0];
  1274. delta <<= TS_SHIFT;
  1275. delta += event->time_delta;
  1276. cpu_buffer->read_stamp += delta;
  1277. return;
  1278. case RINGBUF_TYPE_TIME_STAMP:
  1279. /* FIXME: not implemented */
  1280. return;
  1281. case RINGBUF_TYPE_DATA:
  1282. cpu_buffer->read_stamp += event->time_delta;
  1283. return;
  1284. default:
  1285. BUG();
  1286. }
  1287. return;
  1288. }
  1289. static void
  1290. rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
  1291. struct ring_buffer_event *event)
  1292. {
  1293. u64 delta;
  1294. switch (event->type) {
  1295. case RINGBUF_TYPE_PADDING:
  1296. return;
  1297. case RINGBUF_TYPE_TIME_EXTEND:
  1298. delta = event->array[0];
  1299. delta <<= TS_SHIFT;
  1300. delta += event->time_delta;
  1301. iter->read_stamp += delta;
  1302. return;
  1303. case RINGBUF_TYPE_TIME_STAMP:
  1304. /* FIXME: not implemented */
  1305. return;
  1306. case RINGBUF_TYPE_DATA:
  1307. iter->read_stamp += event->time_delta;
  1308. return;
  1309. default:
  1310. BUG();
  1311. }
  1312. return;
  1313. }
  1314. static struct buffer_page *
  1315. rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
  1316. {
  1317. struct buffer_page *reader = NULL;
  1318. unsigned long flags;
  1319. int nr_loops = 0;
  1320. spin_lock_irqsave(&cpu_buffer->lock, flags);
  1321. again:
  1322. /*
  1323. * This should normally only loop twice. But because the
  1324. * start of the reader inserts an empty page, it causes
  1325. * a case where we will loop three times. There should be no
  1326. * reason to loop four times (that I know of).
  1327. */
  1328. if (unlikely(++nr_loops > 3)) {
  1329. RB_WARN_ON(cpu_buffer, 1);
  1330. reader = NULL;
  1331. goto out;
  1332. }
  1333. reader = cpu_buffer->reader_page;
  1334. /* If there's more to read, return this page */
  1335. if (cpu_buffer->reader_page->read < rb_page_size(reader))
  1336. goto out;
  1337. /* Never should we have an index greater than the size */
  1338. RB_WARN_ON(cpu_buffer,
  1339. cpu_buffer->reader_page->read > rb_page_size(reader));
  1340. /* check if we caught up to the tail */
  1341. reader = NULL;
  1342. if (cpu_buffer->commit_page == cpu_buffer->reader_page)
  1343. goto out;
  1344. /*
  1345. * Splice the empty reader page into the list around the head.
  1346. * Reset the reader page to size zero.
  1347. */
  1348. reader = cpu_buffer->head_page;
  1349. cpu_buffer->reader_page->list.next = reader->list.next;
  1350. cpu_buffer->reader_page->list.prev = reader->list.prev;
  1351. local_set(&cpu_buffer->reader_page->write, 0);
  1352. local_set(&cpu_buffer->reader_page->commit, 0);
  1353. /* Make the reader page now replace the head */
  1354. reader->list.prev->next = &cpu_buffer->reader_page->list;
  1355. reader->list.next->prev = &cpu_buffer->reader_page->list;
  1356. /*
  1357. * If the tail is on the reader, then we must set the head
  1358. * to the inserted page, otherwise we set it one before.
  1359. */
  1360. cpu_buffer->head_page = cpu_buffer->reader_page;
  1361. if (cpu_buffer->commit_page != reader)
  1362. rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
  1363. /* Finally update the reader page to the new head */
  1364. cpu_buffer->reader_page = reader;
  1365. rb_reset_reader_page(cpu_buffer);
  1366. goto again;
  1367. out:
  1368. spin_unlock_irqrestore(&cpu_buffer->lock, flags);
  1369. return reader;
  1370. }
  1371. static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
  1372. {
  1373. struct ring_buffer_event *event;
  1374. struct buffer_page *reader;
  1375. unsigned length;
  1376. reader = rb_get_reader_page(cpu_buffer);
  1377. /* This function should not be called when buffer is empty */
  1378. BUG_ON(!reader);
  1379. event = rb_reader_event(cpu_buffer);
  1380. if (event->type == RINGBUF_TYPE_DATA)
  1381. cpu_buffer->entries--;
  1382. rb_update_read_stamp(cpu_buffer, event);
  1383. length = rb_event_length(event);
  1384. cpu_buffer->reader_page->read += length;
  1385. }
  1386. static void rb_advance_iter(struct ring_buffer_iter *iter)
  1387. {
  1388. struct ring_buffer *buffer;
  1389. struct ring_buffer_per_cpu *cpu_buffer;
  1390. struct ring_buffer_event *event;
  1391. unsigned length;
  1392. cpu_buffer = iter->cpu_buffer;
  1393. buffer = cpu_buffer->buffer;
  1394. /*
  1395. * Check if we are at the end of the buffer.
  1396. */
  1397. if (iter->head >= rb_page_size(iter->head_page)) {
  1398. BUG_ON(iter->head_page == cpu_buffer->commit_page);
  1399. rb_inc_iter(iter);
  1400. return;
  1401. }
  1402. event = rb_iter_head_event(iter);
  1403. length = rb_event_length(event);
  1404. /*
  1405. * This should not be called to advance the header if we are
  1406. * at the tail of the buffer.
  1407. */
  1408. BUG_ON((iter->head_page == cpu_buffer->commit_page) &&
  1409. (iter->head + length > rb_commit_index(cpu_buffer)));
  1410. rb_update_iter_read_stamp(iter, event);
  1411. iter->head += length;
  1412. /* check for end of page padding */
  1413. if ((iter->head >= rb_page_size(iter->head_page)) &&
  1414. (iter->head_page != cpu_buffer->commit_page))
  1415. rb_advance_iter(iter);
  1416. }
  1417. /**
  1418. * ring_buffer_peek - peek at the next event to be read
  1419. * @buffer: The ring buffer to read
  1420. * @cpu: The cpu to peak at
  1421. * @ts: The timestamp counter of this event.
  1422. *
  1423. * This will return the event that will be read next, but does
  1424. * not consume the data.
  1425. */
  1426. struct ring_buffer_event *
  1427. ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
  1428. {
  1429. struct ring_buffer_per_cpu *cpu_buffer;
  1430. struct ring_buffer_event *event;
  1431. struct buffer_page *reader;
  1432. int nr_loops = 0;
  1433. if (!cpu_isset(cpu, buffer->cpumask))
  1434. return NULL;
  1435. cpu_buffer = buffer->buffers[cpu];
  1436. again:
  1437. /*
  1438. * We repeat when a timestamp is encountered. It is possible
  1439. * to get multiple timestamps from an interrupt entering just
  1440. * as one timestamp is about to be written. The max times
  1441. * that this can happen is the number of nested interrupts we
  1442. * can have. Nesting 10 deep of interrupts is clearly
  1443. * an anomaly.
  1444. */
  1445. if (unlikely(++nr_loops > 10)) {
  1446. RB_WARN_ON(cpu_buffer, 1);
  1447. return NULL;
  1448. }
  1449. reader = rb_get_reader_page(cpu_buffer);
  1450. if (!reader)
  1451. return NULL;
  1452. event = rb_reader_event(cpu_buffer);
  1453. switch (event->type) {
  1454. case RINGBUF_TYPE_PADDING:
  1455. RB_WARN_ON(cpu_buffer, 1);
  1456. rb_advance_reader(cpu_buffer);
  1457. return NULL;
  1458. case RINGBUF_TYPE_TIME_EXTEND:
  1459. /* Internal data, OK to advance */
  1460. rb_advance_reader(cpu_buffer);
  1461. goto again;
  1462. case RINGBUF_TYPE_TIME_STAMP:
  1463. /* FIXME: not implemented */
  1464. rb_advance_reader(cpu_buffer);
  1465. goto again;
  1466. case RINGBUF_TYPE_DATA:
  1467. if (ts) {
  1468. *ts = cpu_buffer->read_stamp + event->time_delta;
  1469. ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
  1470. }
  1471. return event;
  1472. default:
  1473. BUG();
  1474. }
  1475. return NULL;
  1476. }
  1477. /**
  1478. * ring_buffer_iter_peek - peek at the next event to be read
  1479. * @iter: The ring buffer iterator
  1480. * @ts: The timestamp counter of this event.
  1481. *
  1482. * This will return the event that will be read next, but does
  1483. * not increment the iterator.
  1484. */
  1485. struct ring_buffer_event *
  1486. ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
  1487. {
  1488. struct ring_buffer *buffer;
  1489. struct ring_buffer_per_cpu *cpu_buffer;
  1490. struct ring_buffer_event *event;
  1491. int nr_loops = 0;
  1492. if (ring_buffer_iter_empty(iter))
  1493. return NULL;
  1494. cpu_buffer = iter->cpu_buffer;
  1495. buffer = cpu_buffer->buffer;
  1496. again:
  1497. /*
  1498. * We repeat when a timestamp is encountered. It is possible
  1499. * to get multiple timestamps from an interrupt entering just
  1500. * as one timestamp is about to be written. The max times
  1501. * that this can happen is the number of nested interrupts we
  1502. * can have. Nesting 10 deep of interrupts is clearly
  1503. * an anomaly.
  1504. */
  1505. if (unlikely(++nr_loops > 10)) {
  1506. RB_WARN_ON(cpu_buffer, 1);
  1507. return NULL;
  1508. }
  1509. if (rb_per_cpu_empty(cpu_buffer))
  1510. return NULL;
  1511. event = rb_iter_head_event(iter);
  1512. switch (event->type) {
  1513. case RINGBUF_TYPE_PADDING:
  1514. rb_inc_iter(iter);
  1515. goto again;
  1516. case RINGBUF_TYPE_TIME_EXTEND:
  1517. /* Internal data, OK to advance */
  1518. rb_advance_iter(iter);
  1519. goto again;
  1520. case RINGBUF_TYPE_TIME_STAMP:
  1521. /* FIXME: not implemented */
  1522. rb_advance_iter(iter);
  1523. goto again;
  1524. case RINGBUF_TYPE_DATA:
  1525. if (ts) {
  1526. *ts = iter->read_stamp + event->time_delta;
  1527. ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
  1528. }
  1529. return event;
  1530. default:
  1531. BUG();
  1532. }
  1533. return NULL;
  1534. }
  1535. /**
  1536. * ring_buffer_consume - return an event and consume it
  1537. * @buffer: The ring buffer to get the next event from
  1538. *
  1539. * Returns the next event in the ring buffer, and that event is consumed.
  1540. * Meaning, that sequential reads will keep returning a different event,
  1541. * and eventually empty the ring buffer if the producer is slower.
  1542. */
  1543. struct ring_buffer_event *
  1544. ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
  1545. {
  1546. struct ring_buffer_per_cpu *cpu_buffer;
  1547. struct ring_buffer_event *event;
  1548. if (!cpu_isset(cpu, buffer->cpumask))
  1549. return NULL;
  1550. event = ring_buffer_peek(buffer, cpu, ts);
  1551. if (!event)
  1552. return NULL;
  1553. cpu_buffer = buffer->buffers[cpu];
  1554. rb_advance_reader(cpu_buffer);
  1555. return event;
  1556. }
  1557. /**
  1558. * ring_buffer_read_start - start a non consuming read of the buffer
  1559. * @buffer: The ring buffer to read from
  1560. * @cpu: The cpu buffer to iterate over
  1561. *
  1562. * This starts up an iteration through the buffer. It also disables
  1563. * the recording to the buffer until the reading is finished.
  1564. * This prevents the reading from being corrupted. This is not
  1565. * a consuming read, so a producer is not expected.
  1566. *
  1567. * Must be paired with ring_buffer_finish.
  1568. */
  1569. struct ring_buffer_iter *
  1570. ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
  1571. {
  1572. struct ring_buffer_per_cpu *cpu_buffer;
  1573. struct ring_buffer_iter *iter;
  1574. unsigned long flags;
  1575. if (!cpu_isset(cpu, buffer->cpumask))
  1576. return NULL;
  1577. iter = kmalloc(sizeof(*iter), GFP_KERNEL);
  1578. if (!iter)
  1579. return NULL;
  1580. cpu_buffer = buffer->buffers[cpu];
  1581. iter->cpu_buffer = cpu_buffer;
  1582. atomic_inc(&cpu_buffer->record_disabled);
  1583. synchronize_sched();
  1584. spin_lock_irqsave(&cpu_buffer->lock, flags);
  1585. ring_buffer_iter_reset(iter);
  1586. spin_unlock_irqrestore(&cpu_buffer->lock, flags);
  1587. return iter;
  1588. }
  1589. /**
  1590. * ring_buffer_finish - finish reading the iterator of the buffer
  1591. * @iter: The iterator retrieved by ring_buffer_start
  1592. *
  1593. * This re-enables the recording to the buffer, and frees the
  1594. * iterator.
  1595. */
  1596. void
  1597. ring_buffer_read_finish(struct ring_buffer_iter *iter)
  1598. {
  1599. struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
  1600. atomic_dec(&cpu_buffer->record_disabled);
  1601. kfree(iter);
  1602. }
  1603. /**
  1604. * ring_buffer_read - read the next item in the ring buffer by the iterator
  1605. * @iter: The ring buffer iterator
  1606. * @ts: The time stamp of the event read.
  1607. *
  1608. * This reads the next event in the ring buffer and increments the iterator.
  1609. */
  1610. struct ring_buffer_event *
  1611. ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
  1612. {
  1613. struct ring_buffer_event *event;
  1614. event = ring_buffer_iter_peek(iter, ts);
  1615. if (!event)
  1616. return NULL;
  1617. rb_advance_iter(iter);
  1618. return event;
  1619. }
  1620. /**
  1621. * ring_buffer_size - return the size of the ring buffer (in bytes)
  1622. * @buffer: The ring buffer.
  1623. */
  1624. unsigned long ring_buffer_size(struct ring_buffer *buffer)
  1625. {
  1626. return BUF_PAGE_SIZE * buffer->pages;
  1627. }
  1628. static void
  1629. rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
  1630. {
  1631. cpu_buffer->head_page
  1632. = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
  1633. local_set(&cpu_buffer->head_page->write, 0);
  1634. local_set(&cpu_buffer->head_page->commit, 0);
  1635. cpu_buffer->head_page->read = 0;
  1636. cpu_buffer->tail_page = cpu_buffer->head_page;
  1637. cpu_buffer->commit_page = cpu_buffer->head_page;
  1638. INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
  1639. local_set(&cpu_buffer->reader_page->write, 0);
  1640. local_set(&cpu_buffer->reader_page->commit, 0);
  1641. cpu_buffer->reader_page->read = 0;
  1642. cpu_buffer->overrun = 0;
  1643. cpu_buffer->entries = 0;
  1644. }
  1645. /**
  1646. * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
  1647. * @buffer: The ring buffer to reset a per cpu buffer of
  1648. * @cpu: The CPU buffer to be reset
  1649. */
  1650. void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
  1651. {
  1652. struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
  1653. unsigned long flags;
  1654. if (!cpu_isset(cpu, buffer->cpumask))
  1655. return;
  1656. spin_lock_irqsave(&cpu_buffer->lock, flags);
  1657. rb_reset_cpu(cpu_buffer);
  1658. spin_unlock_irqrestore(&cpu_buffer->lock, flags);
  1659. }
  1660. /**
  1661. * ring_buffer_reset - reset a ring buffer
  1662. * @buffer: The ring buffer to reset all cpu buffers
  1663. */
  1664. void ring_buffer_reset(struct ring_buffer *buffer)
  1665. {
  1666. int cpu;
  1667. for_each_buffer_cpu(buffer, cpu)
  1668. ring_buffer_reset_cpu(buffer, cpu);
  1669. }
  1670. /**
  1671. * rind_buffer_empty - is the ring buffer empty?
  1672. * @buffer: The ring buffer to test
  1673. */
  1674. int ring_buffer_empty(struct ring_buffer *buffer)
  1675. {
  1676. struct ring_buffer_per_cpu *cpu_buffer;
  1677. int cpu;
  1678. /* yes this is racy, but if you don't like the race, lock the buffer */
  1679. for_each_buffer_cpu(buffer, cpu) {
  1680. cpu_buffer = buffer->buffers[cpu];
  1681. if (!rb_per_cpu_empty(cpu_buffer))
  1682. return 0;
  1683. }
  1684. return 1;
  1685. }
  1686. /**
  1687. * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
  1688. * @buffer: The ring buffer
  1689. * @cpu: The CPU buffer to test
  1690. */
  1691. int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
  1692. {
  1693. struct ring_buffer_per_cpu *cpu_buffer;
  1694. if (!cpu_isset(cpu, buffer->cpumask))
  1695. return 1;
  1696. cpu_buffer = buffer->buffers[cpu];
  1697. return rb_per_cpu_empty(cpu_buffer);
  1698. }
  1699. /**
  1700. * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
  1701. * @buffer_a: One buffer to swap with
  1702. * @buffer_b: The other buffer to swap with
  1703. *
  1704. * This function is useful for tracers that want to take a "snapshot"
  1705. * of a CPU buffer and has another back up buffer lying around.
  1706. * it is expected that the tracer handles the cpu buffer not being
  1707. * used at the moment.
  1708. */
  1709. int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
  1710. struct ring_buffer *buffer_b, int cpu)
  1711. {
  1712. struct ring_buffer_per_cpu *cpu_buffer_a;
  1713. struct ring_buffer_per_cpu *cpu_buffer_b;
  1714. if (!cpu_isset(cpu, buffer_a->cpumask) ||
  1715. !cpu_isset(cpu, buffer_b->cpumask))
  1716. return -EINVAL;
  1717. /* At least make sure the two buffers are somewhat the same */
  1718. if (buffer_a->size != buffer_b->size ||
  1719. buffer_a->pages != buffer_b->pages)
  1720. return -EINVAL;
  1721. cpu_buffer_a = buffer_a->buffers[cpu];
  1722. cpu_buffer_b = buffer_b->buffers[cpu];
  1723. /*
  1724. * We can't do a synchronize_sched here because this
  1725. * function can be called in atomic context.
  1726. * Normally this will be called from the same CPU as cpu.
  1727. * If not it's up to the caller to protect this.
  1728. */
  1729. atomic_inc(&cpu_buffer_a->record_disabled);
  1730. atomic_inc(&cpu_buffer_b->record_disabled);
  1731. buffer_a->buffers[cpu] = cpu_buffer_b;
  1732. buffer_b->buffers[cpu] = cpu_buffer_a;
  1733. cpu_buffer_b->buffer = buffer_a;
  1734. cpu_buffer_a->buffer = buffer_b;
  1735. atomic_dec(&cpu_buffer_a->record_disabled);
  1736. atomic_dec(&cpu_buffer_b->record_disabled);
  1737. return 0;
  1738. }
  1739. static ssize_t
  1740. rb_simple_read(struct file *filp, char __user *ubuf,
  1741. size_t cnt, loff_t *ppos)
  1742. {
  1743. int *p = filp->private_data;
  1744. char buf[64];
  1745. int r;
  1746. /* !ring_buffers_off == tracing_on */
  1747. r = sprintf(buf, "%d\n", !*p);
  1748. return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
  1749. }
  1750. static ssize_t
  1751. rb_simple_write(struct file *filp, const char __user *ubuf,
  1752. size_t cnt, loff_t *ppos)
  1753. {
  1754. int *p = filp->private_data;
  1755. char buf[64];
  1756. long val;
  1757. int ret;
  1758. if (cnt >= sizeof(buf))
  1759. return -EINVAL;
  1760. if (copy_from_user(&buf, ubuf, cnt))
  1761. return -EFAULT;
  1762. buf[cnt] = 0;
  1763. ret = strict_strtoul(buf, 10, &val);
  1764. if (ret < 0)
  1765. return ret;
  1766. /* !ring_buffers_off == tracing_on */
  1767. *p = !val;
  1768. (*ppos)++;
  1769. return cnt;
  1770. }
  1771. static struct file_operations rb_simple_fops = {
  1772. .open = tracing_open_generic,
  1773. .read = rb_simple_read,
  1774. .write = rb_simple_write,
  1775. };
  1776. static __init int rb_init_debugfs(void)
  1777. {
  1778. struct dentry *d_tracer;
  1779. struct dentry *entry;
  1780. d_tracer = tracing_init_dentry();
  1781. entry = debugfs_create_file("tracing_on", 0644, d_tracer,
  1782. &ring_buffers_off, &rb_simple_fops);
  1783. if (!entry)
  1784. pr_warning("Could not create debugfs 'tracing_on' entry\n");
  1785. return 0;
  1786. }
  1787. fs_initcall(rb_init_debugfs);