Commit | Line | Data |
---|---|---|
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> | |
15 | ||
16 | #include "internal.h" | |
17 | ||
18 | static bool perf_output_space(struct ring_buffer *rb, unsigned long tail, | |
19 | unsigned long offset, unsigned long head) | |
20 | { | |
dd9c086d SE |
21 | unsigned long sz = perf_data_size(rb); |
22 | unsigned long mask = sz - 1; | |
76369139 | 23 | |
dd9c086d SE |
24 | /* |
25 | * check if user-writable | |
26 | * overwrite : over-write its own tail | |
27 | * !overwrite: buffer possibly drops events. | |
28 | */ | |
29 | if (rb->overwrite) | |
76369139 FW |
30 | return true; |
31 | ||
dd9c086d SE |
32 | /* |
33 | * verify that payload is not bigger than buffer | |
34 | * otherwise masking logic may fail to detect | |
35 | * the "not enough space" condition | |
36 | */ | |
37 | if ((head - offset) > sz) | |
38 | return false; | |
76369139 FW |
39 | |
40 | offset = (offset - tail) & mask; | |
41 | head = (head - tail) & mask; | |
42 | ||
43 | if ((int)(head - offset) < 0) | |
44 | return false; | |
45 | ||
46 | return true; | |
47 | } | |
48 | ||
49 | static void perf_output_wakeup(struct perf_output_handle *handle) | |
50 | { | |
51 | atomic_set(&handle->rb->poll, POLL_IN); | |
52 | ||
a8b0ca17 PZ |
53 | handle->event->pending_wakeup = 1; |
54 | irq_work_queue(&handle->event->pending); | |
76369139 FW |
55 | } |
56 | ||
57 | /* | |
58 | * We need to ensure a later event_id doesn't publish a head when a former | |
59 | * event isn't done writing. However since we need to deal with NMIs we | |
60 | * cannot fully serialize things. | |
61 | * | |
62 | * We only publish the head (and generate a wakeup) when the outer-most | |
63 | * event completes. | |
64 | */ | |
65 | static void perf_output_get_handle(struct perf_output_handle *handle) | |
66 | { | |
67 | struct ring_buffer *rb = handle->rb; | |
68 | ||
69 | preempt_disable(); | |
70 | local_inc(&rb->nest); | |
71 | handle->wakeup = local_read(&rb->wakeup); | |
72 | } | |
73 | ||
74 | static void perf_output_put_handle(struct perf_output_handle *handle) | |
75 | { | |
76 | struct ring_buffer *rb = handle->rb; | |
77 | unsigned long head; | |
78 | ||
79 | again: | |
80 | head = local_read(&rb->head); | |
81 | ||
82 | /* | |
83 | * IRQ/NMI can happen here, which means we can miss a head update. | |
84 | */ | |
85 | ||
86 | if (!local_dec_and_test(&rb->nest)) | |
87 | goto out; | |
88 | ||
89 | /* | |
bf378d34 PZ |
90 | * Since the mmap() consumer (userspace) can run on a different CPU: |
91 | * | |
92 | * kernel user | |
93 | * | |
94 | * READ ->data_tail READ ->data_head | |
95 | * smp_mb() (A) smp_rmb() (C) | |
96 | * WRITE $data READ $data | |
97 | * smp_wmb() (B) smp_mb() (D) | |
98 | * STORE ->data_head WRITE ->data_tail | |
99 | * | |
100 | * Where A pairs with D, and B pairs with C. | |
101 | * | |
102 | * I don't think A needs to be a full barrier because we won't in fact | |
103 | * write data until we see the store from userspace. So we simply don't | |
104 | * issue the data WRITE until we observe it. Be conservative for now. | |
105 | * | |
106 | * OTOH, D needs to be a full barrier since it separates the data READ | |
107 | * from the tail WRITE. | |
108 | * | |
109 | * For B a WMB is sufficient since it separates two WRITEs, and for C | |
110 | * an RMB is sufficient since it separates two READs. | |
111 | * | |
112 | * See perf_output_begin(). | |
76369139 | 113 | */ |
bf378d34 | 114 | smp_wmb(); |
76369139 FW |
115 | rb->user_page->data_head = head; |
116 | ||
117 | /* | |
118 | * Now check if we missed an update, rely on the (compiler) | |
119 | * barrier in atomic_dec_and_test() to re-read rb->head. | |
120 | */ | |
121 | if (unlikely(head != local_read(&rb->head))) { | |
122 | local_inc(&rb->nest); | |
123 | goto again; | |
124 | } | |
125 | ||
126 | if (handle->wakeup != local_read(&rb->wakeup)) | |
127 | perf_output_wakeup(handle); | |
128 | ||
129 | out: | |
130 | preempt_enable(); | |
131 | } | |
132 | ||
133 | int perf_output_begin(struct perf_output_handle *handle, | |
a7ac67ea | 134 | struct perf_event *event, unsigned int size) |
76369139 FW |
135 | { |
136 | struct ring_buffer *rb; | |
137 | unsigned long tail, offset, head; | |
138 | int have_lost; | |
139 | struct perf_sample_data sample_data; | |
140 | struct { | |
141 | struct perf_event_header header; | |
142 | u64 id; | |
143 | u64 lost; | |
144 | } lost_event; | |
145 | ||
146 | rcu_read_lock(); | |
147 | /* | |
148 | * For inherited events we send all the output towards the parent. | |
149 | */ | |
150 | if (event->parent) | |
151 | event = event->parent; | |
152 | ||
153 | rb = rcu_dereference(event->rb); | |
154 | if (!rb) | |
155 | goto out; | |
156 | ||
157 | handle->rb = rb; | |
158 | handle->event = event; | |
76369139 FW |
159 | |
160 | if (!rb->nr_pages) | |
161 | goto out; | |
162 | ||
163 | have_lost = local_read(&rb->lost); | |
164 | if (have_lost) { | |
165 | lost_event.header.size = sizeof(lost_event); | |
166 | perf_event_header__init_id(&lost_event.header, &sample_data, | |
167 | event); | |
168 | size += lost_event.header.size; | |
169 | } | |
170 | ||
171 | perf_output_get_handle(handle); | |
172 | ||
173 | do { | |
174 | /* | |
175 | * Userspace could choose to issue a mb() before updating the | |
176 | * tail pointer. So that all reads will be completed before the | |
177 | * write is issued. | |
bf378d34 PZ |
178 | * |
179 | * See perf_output_put_handle(). | |
76369139 FW |
180 | */ |
181 | tail = ACCESS_ONCE(rb->user_page->data_tail); | |
bf378d34 | 182 | smp_mb(); |
76369139 FW |
183 | offset = head = local_read(&rb->head); |
184 | head += size; | |
185 | if (unlikely(!perf_output_space(rb, tail, offset, head))) | |
186 | goto fail; | |
187 | } while (local_cmpxchg(&rb->head, offset, head) != offset); | |
188 | ||
189 | if (head - local_read(&rb->wakeup) > rb->watermark) | |
190 | local_add(rb->watermark, &rb->wakeup); | |
191 | ||
192 | handle->page = offset >> (PAGE_SHIFT + page_order(rb)); | |
193 | handle->page &= rb->nr_pages - 1; | |
194 | handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1); | |
195 | handle->addr = rb->data_pages[handle->page]; | |
196 | handle->addr += handle->size; | |
197 | handle->size = (PAGE_SIZE << page_order(rb)) - handle->size; | |
198 | ||
199 | if (have_lost) { | |
200 | lost_event.header.type = PERF_RECORD_LOST; | |
201 | lost_event.header.misc = 0; | |
202 | lost_event.id = event->id; | |
203 | lost_event.lost = local_xchg(&rb->lost, 0); | |
204 | ||
205 | perf_output_put(handle, lost_event); | |
206 | perf_event__output_id_sample(event, handle, &sample_data); | |
207 | } | |
208 | ||
209 | return 0; | |
210 | ||
211 | fail: | |
212 | local_inc(&rb->lost); | |
213 | perf_output_put_handle(handle); | |
214 | out: | |
215 | rcu_read_unlock(); | |
216 | ||
217 | return -ENOSPC; | |
218 | } | |
219 | ||
91d7753a | 220 | unsigned int perf_output_copy(struct perf_output_handle *handle, |
76369139 FW |
221 | const void *buf, unsigned int len) |
222 | { | |
91d7753a | 223 | return __output_copy(handle, buf, len); |
76369139 FW |
224 | } |
225 | ||
5685e0ff JO |
226 | unsigned int perf_output_skip(struct perf_output_handle *handle, |
227 | unsigned int len) | |
228 | { | |
229 | return __output_skip(handle, NULL, len); | |
230 | } | |
231 | ||
76369139 FW |
232 | void perf_output_end(struct perf_output_handle *handle) |
233 | { | |
76369139 FW |
234 | perf_output_put_handle(handle); |
235 | rcu_read_unlock(); | |
236 | } | |
237 | ||
238 | static void | |
239 | ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) | |
240 | { | |
241 | long max_size = perf_data_size(rb); | |
242 | ||
243 | if (watermark) | |
244 | rb->watermark = min(max_size, watermark); | |
245 | ||
246 | if (!rb->watermark) | |
247 | rb->watermark = max_size / 2; | |
248 | ||
249 | if (flags & RING_BUFFER_WRITABLE) | |
dd9c086d SE |
250 | rb->overwrite = 0; |
251 | else | |
252 | rb->overwrite = 1; | |
76369139 FW |
253 | |
254 | atomic_set(&rb->refcount, 1); | |
10c6db11 PZ |
255 | |
256 | INIT_LIST_HEAD(&rb->event_list); | |
257 | spin_lock_init(&rb->event_lock); | |
76369139 FW |
258 | } |
259 | ||
260 | #ifndef CONFIG_PERF_USE_VMALLOC | |
261 | ||
262 | /* | |
263 | * Back perf_mmap() with regular GFP_KERNEL-0 pages. | |
264 | */ | |
265 | ||
266 | struct page * | |
267 | perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff) | |
268 | { | |
269 | if (pgoff > rb->nr_pages) | |
270 | return NULL; | |
271 | ||
272 | if (pgoff == 0) | |
273 | return virt_to_page(rb->user_page); | |
274 | ||
275 | return virt_to_page(rb->data_pages[pgoff - 1]); | |
276 | } | |
277 | ||
278 | static void *perf_mmap_alloc_page(int cpu) | |
279 | { | |
280 | struct page *page; | |
281 | int node; | |
282 | ||
283 | node = (cpu == -1) ? cpu : cpu_to_node(cpu); | |
284 | page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); | |
285 | if (!page) | |
286 | return NULL; | |
287 | ||
288 | return page_address(page); | |
289 | } | |
290 | ||
291 | struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) | |
292 | { | |
293 | struct ring_buffer *rb; | |
294 | unsigned long size; | |
295 | int i; | |
296 | ||
297 | size = sizeof(struct ring_buffer); | |
298 | size += nr_pages * sizeof(void *); | |
299 | ||
300 | rb = kzalloc(size, GFP_KERNEL); | |
301 | if (!rb) | |
302 | goto fail; | |
303 | ||
304 | rb->user_page = perf_mmap_alloc_page(cpu); | |
305 | if (!rb->user_page) | |
306 | goto fail_user_page; | |
307 | ||
308 | for (i = 0; i < nr_pages; i++) { | |
309 | rb->data_pages[i] = perf_mmap_alloc_page(cpu); | |
310 | if (!rb->data_pages[i]) | |
311 | goto fail_data_pages; | |
312 | } | |
313 | ||
314 | rb->nr_pages = nr_pages; | |
315 | ||
316 | ring_buffer_init(rb, watermark, flags); | |
317 | ||
318 | return rb; | |
319 | ||
320 | fail_data_pages: | |
321 | for (i--; i >= 0; i--) | |
322 | free_page((unsigned long)rb->data_pages[i]); | |
323 | ||
324 | free_page((unsigned long)rb->user_page); | |
325 | ||
326 | fail_user_page: | |
327 | kfree(rb); | |
328 | ||
329 | fail: | |
330 | return NULL; | |
331 | } | |
332 | ||
333 | static void perf_mmap_free_page(unsigned long addr) | |
334 | { | |
335 | struct page *page = virt_to_page((void *)addr); | |
336 | ||
337 | page->mapping = NULL; | |
338 | __free_page(page); | |
339 | } | |
340 | ||
341 | void rb_free(struct ring_buffer *rb) | |
342 | { | |
343 | int i; | |
344 | ||
345 | perf_mmap_free_page((unsigned long)rb->user_page); | |
346 | for (i = 0; i < rb->nr_pages; i++) | |
347 | perf_mmap_free_page((unsigned long)rb->data_pages[i]); | |
348 | kfree(rb); | |
349 | } | |
350 | ||
351 | #else | |
5919b309 JO |
352 | static int data_page_nr(struct ring_buffer *rb) |
353 | { | |
354 | return rb->nr_pages << page_order(rb); | |
355 | } | |
76369139 FW |
356 | |
357 | struct page * | |
358 | perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff) | |
359 | { | |
5919b309 JO |
360 | /* The '>' counts in the user page. */ |
361 | if (pgoff > data_page_nr(rb)) | |
76369139 FW |
362 | return NULL; |
363 | ||
364 | return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE); | |
365 | } | |
366 | ||
367 | static void perf_mmap_unmark_page(void *addr) | |
368 | { | |
369 | struct page *page = vmalloc_to_page(addr); | |
370 | ||
371 | page->mapping = NULL; | |
372 | } | |
373 | ||
374 | static void rb_free_work(struct work_struct *work) | |
375 | { | |
376 | struct ring_buffer *rb; | |
377 | void *base; | |
378 | int i, nr; | |
379 | ||
380 | rb = container_of(work, struct ring_buffer, work); | |
5919b309 | 381 | nr = data_page_nr(rb); |
76369139 FW |
382 | |
383 | base = rb->user_page; | |
5919b309 JO |
384 | /* The '<=' counts in the user page. */ |
385 | for (i = 0; i <= nr; i++) | |
76369139 FW |
386 | perf_mmap_unmark_page(base + (i * PAGE_SIZE)); |
387 | ||
388 | vfree(base); | |
389 | kfree(rb); | |
390 | } | |
391 | ||
392 | void rb_free(struct ring_buffer *rb) | |
393 | { | |
394 | schedule_work(&rb->work); | |
395 | } | |
396 | ||
397 | struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) | |
398 | { | |
399 | struct ring_buffer *rb; | |
400 | unsigned long size; | |
401 | void *all_buf; | |
402 | ||
403 | size = sizeof(struct ring_buffer); | |
404 | size += sizeof(void *); | |
405 | ||
406 | rb = kzalloc(size, GFP_KERNEL); | |
407 | if (!rb) | |
408 | goto fail; | |
409 | ||
410 | INIT_WORK(&rb->work, rb_free_work); | |
411 | ||
412 | all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE); | |
413 | if (!all_buf) | |
414 | goto fail_all_buf; | |
415 | ||
416 | rb->user_page = all_buf; | |
417 | rb->data_pages[0] = all_buf + PAGE_SIZE; | |
418 | rb->page_order = ilog2(nr_pages); | |
5919b309 | 419 | rb->nr_pages = !!nr_pages; |
76369139 FW |
420 | |
421 | ring_buffer_init(rb, watermark, flags); | |
422 | ||
423 | return rb; | |
424 | ||
425 | fail_all_buf: | |
426 | kfree(rb); | |
427 | ||
428 | fail: | |
429 | return NULL; | |
430 | } | |
431 | ||
432 | #endif |