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76369139 FW |
1 | /* |
2 | * Performance events ring-buffer code: | |
3 | * | |
4 | * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de> | |
5 | * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar | |
6 | * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> | |
d36b6910 | 7 | * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com> |
76369139 FW |
8 | * |
9 | * For licensing details see kernel-base/COPYING | |
10 | */ | |
11 | ||
12 | #include <linux/perf_event.h> | |
13 | #include <linux/vmalloc.h> | |
14 | #include <linux/slab.h> | |
26c86da8 | 15 | #include <linux/circ_buf.h> |
7c60fc0e | 16 | #include <linux/poll.h> |
76369139 FW |
17 | |
18 | #include "internal.h" | |
19 | ||
76369139 FW |
20 | static void perf_output_wakeup(struct perf_output_handle *handle) |
21 | { | |
7c60fc0e | 22 | atomic_set(&handle->rb->poll, POLLIN); |
76369139 | 23 | |
a8b0ca17 PZ |
24 | handle->event->pending_wakeup = 1; |
25 | irq_work_queue(&handle->event->pending); | |
76369139 FW |
26 | } |
27 | ||
28 | /* | |
29 | * We need to ensure a later event_id doesn't publish a head when a former | |
30 | * event isn't done writing. However since we need to deal with NMIs we | |
31 | * cannot fully serialize things. | |
32 | * | |
33 | * We only publish the head (and generate a wakeup) when the outer-most | |
34 | * event completes. | |
35 | */ | |
36 | static void perf_output_get_handle(struct perf_output_handle *handle) | |
37 | { | |
38 | struct ring_buffer *rb = handle->rb; | |
39 | ||
40 | preempt_disable(); | |
41 | local_inc(&rb->nest); | |
42 | handle->wakeup = local_read(&rb->wakeup); | |
43 | } | |
44 | ||
45 | static void perf_output_put_handle(struct perf_output_handle *handle) | |
46 | { | |
47 | struct ring_buffer *rb = handle->rb; | |
48 | unsigned long head; | |
49 | ||
50 | again: | |
51 | head = local_read(&rb->head); | |
52 | ||
53 | /* | |
54 | * IRQ/NMI can happen here, which means we can miss a head update. | |
55 | */ | |
56 | ||
57 | if (!local_dec_and_test(&rb->nest)) | |
58 | goto out; | |
59 | ||
60 | /* | |
bf378d34 PZ |
61 | * Since the mmap() consumer (userspace) can run on a different CPU: |
62 | * | |
63 | * kernel user | |
64 | * | |
c7f2e3cd PZ |
65 | * if (LOAD ->data_tail) { LOAD ->data_head |
66 | * (A) smp_rmb() (C) | |
67 | * STORE $data LOAD $data | |
68 | * smp_wmb() (B) smp_mb() (D) | |
69 | * STORE ->data_head STORE ->data_tail | |
70 | * } | |
bf378d34 PZ |
71 | * |
72 | * Where A pairs with D, and B pairs with C. | |
73 | * | |
c7f2e3cd PZ |
74 | * In our case (A) is a control dependency that separates the load of |
75 | * the ->data_tail and the stores of $data. In case ->data_tail | |
76 | * indicates there is no room in the buffer to store $data we do not. | |
bf378d34 | 77 | * |
c7f2e3cd | 78 | * D needs to be a full barrier since it separates the data READ |
bf378d34 PZ |
79 | * from the tail WRITE. |
80 | * | |
81 | * For B a WMB is sufficient since it separates two WRITEs, and for C | |
82 | * an RMB is sufficient since it separates two READs. | |
83 | * | |
84 | * See perf_output_begin(). | |
76369139 | 85 | */ |
c7f2e3cd | 86 | smp_wmb(); /* B, matches C */ |
76369139 FW |
87 | rb->user_page->data_head = head; |
88 | ||
89 | /* | |
394570b7 PZ |
90 | * Now check if we missed an update -- rely on previous implied |
91 | * compiler barriers to force a re-read. | |
76369139 FW |
92 | */ |
93 | if (unlikely(head != local_read(&rb->head))) { | |
94 | local_inc(&rb->nest); | |
95 | goto again; | |
96 | } | |
97 | ||
98 | if (handle->wakeup != local_read(&rb->wakeup)) | |
99 | perf_output_wakeup(handle); | |
100 | ||
101 | out: | |
102 | preempt_enable(); | |
103 | } | |
104 | ||
105 | int perf_output_begin(struct perf_output_handle *handle, | |
a7ac67ea | 106 | struct perf_event *event, unsigned int size) |
76369139 FW |
107 | { |
108 | struct ring_buffer *rb; | |
109 | unsigned long tail, offset, head; | |
524feca5 | 110 | int have_lost, page_shift; |
76369139 FW |
111 | struct { |
112 | struct perf_event_header header; | |
113 | u64 id; | |
114 | u64 lost; | |
115 | } lost_event; | |
116 | ||
117 | rcu_read_lock(); | |
118 | /* | |
119 | * For inherited events we send all the output towards the parent. | |
120 | */ | |
121 | if (event->parent) | |
122 | event = event->parent; | |
123 | ||
124 | rb = rcu_dereference(event->rb); | |
c72b42a3 | 125 | if (unlikely(!rb)) |
76369139 FW |
126 | goto out; |
127 | ||
c72b42a3 | 128 | if (unlikely(!rb->nr_pages)) |
76369139 FW |
129 | goto out; |
130 | ||
c72b42a3 PZ |
131 | handle->rb = rb; |
132 | handle->event = event; | |
133 | ||
76369139 | 134 | have_lost = local_read(&rb->lost); |
c72b42a3 | 135 | if (unlikely(have_lost)) { |
d20a973f PZ |
136 | size += sizeof(lost_event); |
137 | if (event->attr.sample_id_all) | |
138 | size += event->id_header_size; | |
76369139 FW |
139 | } |
140 | ||
141 | perf_output_get_handle(handle); | |
142 | ||
143 | do { | |
76369139 | 144 | tail = ACCESS_ONCE(rb->user_page->data_tail); |
76369139 | 145 | offset = head = local_read(&rb->head); |
26c86da8 PZ |
146 | if (!rb->overwrite && |
147 | unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size)) | |
76369139 | 148 | goto fail; |
c7f2e3cd PZ |
149 | |
150 | /* | |
151 | * The above forms a control dependency barrier separating the | |
152 | * @tail load above from the data stores below. Since the @tail | |
153 | * load is required to compute the branch to fail below. | |
154 | * | |
155 | * A, matches D; the full memory barrier userspace SHOULD issue | |
156 | * after reading the data and before storing the new tail | |
157 | * position. | |
158 | * | |
159 | * See perf_output_put_handle(). | |
160 | */ | |
161 | ||
26c86da8 | 162 | head += size; |
76369139 FW |
163 | } while (local_cmpxchg(&rb->head, offset, head) != offset); |
164 | ||
85f59edf | 165 | /* |
c7f2e3cd PZ |
166 | * We rely on the implied barrier() by local_cmpxchg() to ensure |
167 | * none of the data stores below can be lifted up by the compiler. | |
85f59edf | 168 | */ |
85f59edf | 169 | |
c72b42a3 | 170 | if (unlikely(head - local_read(&rb->wakeup) > rb->watermark)) |
76369139 FW |
171 | local_add(rb->watermark, &rb->wakeup); |
172 | ||
524feca5 PZ |
173 | page_shift = PAGE_SHIFT + page_order(rb); |
174 | ||
175 | handle->page = (offset >> page_shift) & (rb->nr_pages - 1); | |
176 | offset &= (1UL << page_shift) - 1; | |
177 | handle->addr = rb->data_pages[handle->page] + offset; | |
178 | handle->size = (1UL << page_shift) - offset; | |
76369139 | 179 | |
c72b42a3 | 180 | if (unlikely(have_lost)) { |
d20a973f PZ |
181 | struct perf_sample_data sample_data; |
182 | ||
183 | lost_event.header.size = sizeof(lost_event); | |
76369139 FW |
184 | lost_event.header.type = PERF_RECORD_LOST; |
185 | lost_event.header.misc = 0; | |
186 | lost_event.id = event->id; | |
187 | lost_event.lost = local_xchg(&rb->lost, 0); | |
188 | ||
d20a973f PZ |
189 | perf_event_header__init_id(&lost_event.header, |
190 | &sample_data, event); | |
76369139 FW |
191 | perf_output_put(handle, lost_event); |
192 | perf_event__output_id_sample(event, handle, &sample_data); | |
193 | } | |
194 | ||
195 | return 0; | |
196 | ||
197 | fail: | |
198 | local_inc(&rb->lost); | |
199 | perf_output_put_handle(handle); | |
200 | out: | |
201 | rcu_read_unlock(); | |
202 | ||
203 | return -ENOSPC; | |
204 | } | |
205 | ||
91d7753a | 206 | unsigned int perf_output_copy(struct perf_output_handle *handle, |
76369139 FW |
207 | const void *buf, unsigned int len) |
208 | { | |
91d7753a | 209 | return __output_copy(handle, buf, len); |
76369139 FW |
210 | } |
211 | ||
5685e0ff JO |
212 | unsigned int perf_output_skip(struct perf_output_handle *handle, |
213 | unsigned int len) | |
214 | { | |
215 | return __output_skip(handle, NULL, len); | |
216 | } | |
217 | ||
76369139 FW |
218 | void perf_output_end(struct perf_output_handle *handle) |
219 | { | |
76369139 FW |
220 | perf_output_put_handle(handle); |
221 | rcu_read_unlock(); | |
222 | } | |
223 | ||
224 | static void | |
225 | ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) | |
226 | { | |
227 | long max_size = perf_data_size(rb); | |
228 | ||
229 | if (watermark) | |
230 | rb->watermark = min(max_size, watermark); | |
231 | ||
232 | if (!rb->watermark) | |
233 | rb->watermark = max_size / 2; | |
234 | ||
235 | if (flags & RING_BUFFER_WRITABLE) | |
dd9c086d SE |
236 | rb->overwrite = 0; |
237 | else | |
238 | rb->overwrite = 1; | |
76369139 FW |
239 | |
240 | atomic_set(&rb->refcount, 1); | |
10c6db11 PZ |
241 | |
242 | INIT_LIST_HEAD(&rb->event_list); | |
243 | spin_lock_init(&rb->event_lock); | |
76369139 FW |
244 | } |
245 | ||
246 | #ifndef CONFIG_PERF_USE_VMALLOC | |
247 | ||
248 | /* | |
249 | * Back perf_mmap() with regular GFP_KERNEL-0 pages. | |
250 | */ | |
251 | ||
252 | struct page * | |
253 | perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff) | |
254 | { | |
255 | if (pgoff > rb->nr_pages) | |
256 | return NULL; | |
257 | ||
258 | if (pgoff == 0) | |
259 | return virt_to_page(rb->user_page); | |
260 | ||
261 | return virt_to_page(rb->data_pages[pgoff - 1]); | |
262 | } | |
263 | ||
264 | static void *perf_mmap_alloc_page(int cpu) | |
265 | { | |
266 | struct page *page; | |
267 | int node; | |
268 | ||
269 | node = (cpu == -1) ? cpu : cpu_to_node(cpu); | |
270 | page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); | |
271 | if (!page) | |
272 | return NULL; | |
273 | ||
274 | return page_address(page); | |
275 | } | |
276 | ||
277 | struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) | |
278 | { | |
279 | struct ring_buffer *rb; | |
280 | unsigned long size; | |
281 | int i; | |
282 | ||
283 | size = sizeof(struct ring_buffer); | |
284 | size += nr_pages * sizeof(void *); | |
285 | ||
286 | rb = kzalloc(size, GFP_KERNEL); | |
287 | if (!rb) | |
288 | goto fail; | |
289 | ||
290 | rb->user_page = perf_mmap_alloc_page(cpu); | |
291 | if (!rb->user_page) | |
292 | goto fail_user_page; | |
293 | ||
294 | for (i = 0; i < nr_pages; i++) { | |
295 | rb->data_pages[i] = perf_mmap_alloc_page(cpu); | |
296 | if (!rb->data_pages[i]) | |
297 | goto fail_data_pages; | |
298 | } | |
299 | ||
300 | rb->nr_pages = nr_pages; | |
301 | ||
302 | ring_buffer_init(rb, watermark, flags); | |
303 | ||
304 | return rb; | |
305 | ||
306 | fail_data_pages: | |
307 | for (i--; i >= 0; i--) | |
308 | free_page((unsigned long)rb->data_pages[i]); | |
309 | ||
310 | free_page((unsigned long)rb->user_page); | |
311 | ||
312 | fail_user_page: | |
313 | kfree(rb); | |
314 | ||
315 | fail: | |
316 | return NULL; | |
317 | } | |
318 | ||
319 | static void perf_mmap_free_page(unsigned long addr) | |
320 | { | |
321 | struct page *page = virt_to_page((void *)addr); | |
322 | ||
323 | page->mapping = NULL; | |
324 | __free_page(page); | |
325 | } | |
326 | ||
327 | void rb_free(struct ring_buffer *rb) | |
328 | { | |
329 | int i; | |
330 | ||
331 | perf_mmap_free_page((unsigned long)rb->user_page); | |
332 | for (i = 0; i < rb->nr_pages; i++) | |
333 | perf_mmap_free_page((unsigned long)rb->data_pages[i]); | |
334 | kfree(rb); | |
335 | } | |
336 | ||
337 | #else | |
5919b309 JO |
338 | static int data_page_nr(struct ring_buffer *rb) |
339 | { | |
340 | return rb->nr_pages << page_order(rb); | |
341 | } | |
76369139 FW |
342 | |
343 | struct page * | |
344 | perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff) | |
345 | { | |
5919b309 JO |
346 | /* The '>' counts in the user page. */ |
347 | if (pgoff > data_page_nr(rb)) | |
76369139 FW |
348 | return NULL; |
349 | ||
350 | return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE); | |
351 | } | |
352 | ||
353 | static void perf_mmap_unmark_page(void *addr) | |
354 | { | |
355 | struct page *page = vmalloc_to_page(addr); | |
356 | ||
357 | page->mapping = NULL; | |
358 | } | |
359 | ||
360 | static void rb_free_work(struct work_struct *work) | |
361 | { | |
362 | struct ring_buffer *rb; | |
363 | void *base; | |
364 | int i, nr; | |
365 | ||
366 | rb = container_of(work, struct ring_buffer, work); | |
5919b309 | 367 | nr = data_page_nr(rb); |
76369139 FW |
368 | |
369 | base = rb->user_page; | |
5919b309 JO |
370 | /* The '<=' counts in the user page. */ |
371 | for (i = 0; i <= nr; i++) | |
76369139 FW |
372 | perf_mmap_unmark_page(base + (i * PAGE_SIZE)); |
373 | ||
374 | vfree(base); | |
375 | kfree(rb); | |
376 | } | |
377 | ||
378 | void rb_free(struct ring_buffer *rb) | |
379 | { | |
380 | schedule_work(&rb->work); | |
381 | } | |
382 | ||
383 | struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) | |
384 | { | |
385 | struct ring_buffer *rb; | |
386 | unsigned long size; | |
387 | void *all_buf; | |
388 | ||
389 | size = sizeof(struct ring_buffer); | |
390 | size += sizeof(void *); | |
391 | ||
392 | rb = kzalloc(size, GFP_KERNEL); | |
393 | if (!rb) | |
394 | goto fail; | |
395 | ||
396 | INIT_WORK(&rb->work, rb_free_work); | |
397 | ||
398 | all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE); | |
399 | if (!all_buf) | |
400 | goto fail_all_buf; | |
401 | ||
402 | rb->user_page = all_buf; | |
403 | rb->data_pages[0] = all_buf + PAGE_SIZE; | |
404 | rb->page_order = ilog2(nr_pages); | |
5919b309 | 405 | rb->nr_pages = !!nr_pages; |
76369139 FW |
406 | |
407 | ring_buffer_init(rb, watermark, flags); | |
408 | ||
409 | return rb; | |
410 | ||
411 | fail_all_buf: | |
412 | kfree(rb); | |
413 | ||
414 | fail: | |
415 | return NULL; | |
416 | } | |
417 | ||
418 | #endif |