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