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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 | /* | |
88 | * Now check if we missed an update, rely on the (compiler) | |
89 | * barrier in atomic_dec_and_test() to re-read rb->head. | |
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; | |
108 | int have_lost; | |
109 | struct perf_sample_data sample_data; | |
110 | struct { | |
111 | struct perf_event_header header; | |
112 | u64 id; | |
113 | u64 lost; | |
114 | } lost_event; | |
115 | ||
116 | rcu_read_lock(); | |
117 | /* | |
118 | * For inherited events we send all the output towards the parent. | |
119 | */ | |
120 | if (event->parent) | |
121 | event = event->parent; | |
122 | ||
123 | rb = rcu_dereference(event->rb); | |
c72b42a3 | 124 | if (unlikely(!rb)) |
76369139 FW |
125 | goto out; |
126 | ||
c72b42a3 | 127 | if (unlikely(!rb->nr_pages)) |
76369139 FW |
128 | goto out; |
129 | ||
c72b42a3 PZ |
130 | handle->rb = rb; |
131 | handle->event = event; | |
132 | ||
76369139 | 133 | have_lost = local_read(&rb->lost); |
c72b42a3 | 134 | if (unlikely(have_lost)) { |
76369139 FW |
135 | lost_event.header.size = sizeof(lost_event); |
136 | perf_event_header__init_id(&lost_event.header, &sample_data, | |
137 | event); | |
138 | size += lost_event.header.size; | |
139 | } | |
140 | ||
141 | perf_output_get_handle(handle); | |
142 | ||
143 | do { | |
144 | /* | |
145 | * Userspace could choose to issue a mb() before updating the | |
146 | * tail pointer. So that all reads will be completed before the | |
147 | * write is issued. | |
bf378d34 PZ |
148 | * |
149 | * See perf_output_put_handle(). | |
76369139 FW |
150 | */ |
151 | tail = ACCESS_ONCE(rb->user_page->data_tail); | |
bf378d34 | 152 | smp_mb(); |
76369139 | 153 | offset = head = local_read(&rb->head); |
26c86da8 PZ |
154 | if (!rb->overwrite && |
155 | unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size)) | |
76369139 | 156 | goto fail; |
26c86da8 | 157 | head += size; |
76369139 FW |
158 | } while (local_cmpxchg(&rb->head, offset, head) != offset); |
159 | ||
c72b42a3 | 160 | if (unlikely(head - local_read(&rb->wakeup) > rb->watermark)) |
76369139 FW |
161 | local_add(rb->watermark, &rb->wakeup); |
162 | ||
163 | handle->page = offset >> (PAGE_SHIFT + page_order(rb)); | |
164 | handle->page &= rb->nr_pages - 1; | |
165 | handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1); | |
166 | handle->addr = rb->data_pages[handle->page]; | |
167 | handle->addr += handle->size; | |
168 | handle->size = (PAGE_SIZE << page_order(rb)) - handle->size; | |
169 | ||
c72b42a3 | 170 | if (unlikely(have_lost)) { |
76369139 FW |
171 | lost_event.header.type = PERF_RECORD_LOST; |
172 | lost_event.header.misc = 0; | |
173 | lost_event.id = event->id; | |
174 | lost_event.lost = local_xchg(&rb->lost, 0); | |
175 | ||
176 | perf_output_put(handle, lost_event); | |
177 | perf_event__output_id_sample(event, handle, &sample_data); | |
178 | } | |
179 | ||
180 | return 0; | |
181 | ||
182 | fail: | |
183 | local_inc(&rb->lost); | |
184 | perf_output_put_handle(handle); | |
185 | out: | |
186 | rcu_read_unlock(); | |
187 | ||
188 | return -ENOSPC; | |
189 | } | |
190 | ||
91d7753a | 191 | unsigned int perf_output_copy(struct perf_output_handle *handle, |
76369139 FW |
192 | const void *buf, unsigned int len) |
193 | { | |
91d7753a | 194 | return __output_copy(handle, buf, len); |
76369139 FW |
195 | } |
196 | ||
5685e0ff JO |
197 | unsigned int perf_output_skip(struct perf_output_handle *handle, |
198 | unsigned int len) | |
199 | { | |
200 | return __output_skip(handle, NULL, len); | |
201 | } | |
202 | ||
76369139 FW |
203 | void perf_output_end(struct perf_output_handle *handle) |
204 | { | |
76369139 FW |
205 | perf_output_put_handle(handle); |
206 | rcu_read_unlock(); | |
207 | } | |
208 | ||
209 | static void | |
210 | ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) | |
211 | { | |
212 | long max_size = perf_data_size(rb); | |
213 | ||
214 | if (watermark) | |
215 | rb->watermark = min(max_size, watermark); | |
216 | ||
217 | if (!rb->watermark) | |
218 | rb->watermark = max_size / 2; | |
219 | ||
220 | if (flags & RING_BUFFER_WRITABLE) | |
dd9c086d SE |
221 | rb->overwrite = 0; |
222 | else | |
223 | rb->overwrite = 1; | |
76369139 FW |
224 | |
225 | atomic_set(&rb->refcount, 1); | |
10c6db11 PZ |
226 | |
227 | INIT_LIST_HEAD(&rb->event_list); | |
228 | spin_lock_init(&rb->event_lock); | |
76369139 FW |
229 | } |
230 | ||
231 | #ifndef CONFIG_PERF_USE_VMALLOC | |
232 | ||
233 | /* | |
234 | * Back perf_mmap() with regular GFP_KERNEL-0 pages. | |
235 | */ | |
236 | ||
237 | struct page * | |
238 | perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff) | |
239 | { | |
240 | if (pgoff > rb->nr_pages) | |
241 | return NULL; | |
242 | ||
243 | if (pgoff == 0) | |
244 | return virt_to_page(rb->user_page); | |
245 | ||
246 | return virt_to_page(rb->data_pages[pgoff - 1]); | |
247 | } | |
248 | ||
249 | static void *perf_mmap_alloc_page(int cpu) | |
250 | { | |
251 | struct page *page; | |
252 | int node; | |
253 | ||
254 | node = (cpu == -1) ? cpu : cpu_to_node(cpu); | |
255 | page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); | |
256 | if (!page) | |
257 | return NULL; | |
258 | ||
259 | return page_address(page); | |
260 | } | |
261 | ||
262 | struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) | |
263 | { | |
264 | struct ring_buffer *rb; | |
265 | unsigned long size; | |
266 | int i; | |
267 | ||
268 | size = sizeof(struct ring_buffer); | |
269 | size += nr_pages * sizeof(void *); | |
270 | ||
271 | rb = kzalloc(size, GFP_KERNEL); | |
272 | if (!rb) | |
273 | goto fail; | |
274 | ||
275 | rb->user_page = perf_mmap_alloc_page(cpu); | |
276 | if (!rb->user_page) | |
277 | goto fail_user_page; | |
278 | ||
279 | for (i = 0; i < nr_pages; i++) { | |
280 | rb->data_pages[i] = perf_mmap_alloc_page(cpu); | |
281 | if (!rb->data_pages[i]) | |
282 | goto fail_data_pages; | |
283 | } | |
284 | ||
285 | rb->nr_pages = nr_pages; | |
286 | ||
287 | ring_buffer_init(rb, watermark, flags); | |
288 | ||
289 | return rb; | |
290 | ||
291 | fail_data_pages: | |
292 | for (i--; i >= 0; i--) | |
293 | free_page((unsigned long)rb->data_pages[i]); | |
294 | ||
295 | free_page((unsigned long)rb->user_page); | |
296 | ||
297 | fail_user_page: | |
298 | kfree(rb); | |
299 | ||
300 | fail: | |
301 | return NULL; | |
302 | } | |
303 | ||
304 | static void perf_mmap_free_page(unsigned long addr) | |
305 | { | |
306 | struct page *page = virt_to_page((void *)addr); | |
307 | ||
308 | page->mapping = NULL; | |
309 | __free_page(page); | |
310 | } | |
311 | ||
312 | void rb_free(struct ring_buffer *rb) | |
313 | { | |
314 | int i; | |
315 | ||
316 | perf_mmap_free_page((unsigned long)rb->user_page); | |
317 | for (i = 0; i < rb->nr_pages; i++) | |
318 | perf_mmap_free_page((unsigned long)rb->data_pages[i]); | |
319 | kfree(rb); | |
320 | } | |
321 | ||
322 | #else | |
5919b309 JO |
323 | static int data_page_nr(struct ring_buffer *rb) |
324 | { | |
325 | return rb->nr_pages << page_order(rb); | |
326 | } | |
76369139 FW |
327 | |
328 | struct page * | |
329 | perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff) | |
330 | { | |
5919b309 JO |
331 | /* The '>' counts in the user page. */ |
332 | if (pgoff > data_page_nr(rb)) | |
76369139 FW |
333 | return NULL; |
334 | ||
335 | return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE); | |
336 | } | |
337 | ||
338 | static void perf_mmap_unmark_page(void *addr) | |
339 | { | |
340 | struct page *page = vmalloc_to_page(addr); | |
341 | ||
342 | page->mapping = NULL; | |
343 | } | |
344 | ||
345 | static void rb_free_work(struct work_struct *work) | |
346 | { | |
347 | struct ring_buffer *rb; | |
348 | void *base; | |
349 | int i, nr; | |
350 | ||
351 | rb = container_of(work, struct ring_buffer, work); | |
5919b309 | 352 | nr = data_page_nr(rb); |
76369139 FW |
353 | |
354 | base = rb->user_page; | |
5919b309 JO |
355 | /* The '<=' counts in the user page. */ |
356 | for (i = 0; i <= nr; i++) | |
76369139 FW |
357 | perf_mmap_unmark_page(base + (i * PAGE_SIZE)); |
358 | ||
359 | vfree(base); | |
360 | kfree(rb); | |
361 | } | |
362 | ||
363 | void rb_free(struct ring_buffer *rb) | |
364 | { | |
365 | schedule_work(&rb->work); | |
366 | } | |
367 | ||
368 | struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) | |
369 | { | |
370 | struct ring_buffer *rb; | |
371 | unsigned long size; | |
372 | void *all_buf; | |
373 | ||
374 | size = sizeof(struct ring_buffer); | |
375 | size += sizeof(void *); | |
376 | ||
377 | rb = kzalloc(size, GFP_KERNEL); | |
378 | if (!rb) | |
379 | goto fail; | |
380 | ||
381 | INIT_WORK(&rb->work, rb_free_work); | |
382 | ||
383 | all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE); | |
384 | if (!all_buf) | |
385 | goto fail_all_buf; | |
386 | ||
387 | rb->user_page = all_buf; | |
388 | rb->data_pages[0] = all_buf + PAGE_SIZE; | |
389 | rb->page_order = ilog2(nr_pages); | |
5919b309 | 390 | rb->nr_pages = !!nr_pages; |
76369139 FW |
391 | |
392 | ring_buffer_init(rb, watermark, flags); | |
393 | ||
394 | return rb; | |
395 | ||
396 | fail_all_buf: | |
397 | kfree(rb); | |
398 | ||
399 | fail: | |
400 | return NULL; | |
401 | } | |
402 | ||
403 | #endif |