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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>
7 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
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
18static bool perf_output_space(struct ring_buffer *rb, unsigned long tail,
19 unsigned long offset, unsigned long head)
20{
21 unsigned long mask;
22
23 if (!rb->writable)
24 return true;
25
26 mask = perf_data_size(rb) - 1;
27
28 offset = (offset - tail) & mask;
29 head = (head - tail) & mask;
30
31 if ((int)(head - offset) < 0)
32 return false;
33
34 return true;
35}
36
37static void perf_output_wakeup(struct perf_output_handle *handle)
38{
39 atomic_set(&handle->rb->poll, POLL_IN);
40
41 handle->event->pending_wakeup = 1;
42 irq_work_queue(&handle->event->pending);
43}
44
45/*
46 * We need to ensure a later event_id doesn't publish a head when a former
47 * event isn't done writing. However since we need to deal with NMIs we
48 * cannot fully serialize things.
49 *
50 * We only publish the head (and generate a wakeup) when the outer-most
51 * event completes.
52 */
53static void perf_output_get_handle(struct perf_output_handle *handle)
54{
55 struct ring_buffer *rb = handle->rb;
56
57 preempt_disable();
58 local_inc(&rb->nest);
59 handle->wakeup = local_read(&rb->wakeup);
60}
61
62static void perf_output_put_handle(struct perf_output_handle *handle)
63{
64 struct ring_buffer *rb = handle->rb;
65 unsigned long head;
66
67again:
68 head = local_read(&rb->head);
69
70 /*
71 * IRQ/NMI can happen here, which means we can miss a head update.
72 */
73
74 if (!local_dec_and_test(&rb->nest))
75 goto out;
76
77 /*
78 * Publish the known good head. Rely on the full barrier implied
79 * by atomic_dec_and_test() order the rb->head read and this
80 * write.
81 */
82 rb->user_page->data_head = head;
83
84 /*
85 * Now check if we missed an update, rely on the (compiler)
86 * barrier in atomic_dec_and_test() to re-read rb->head.
87 */
88 if (unlikely(head != local_read(&rb->head))) {
89 local_inc(&rb->nest);
90 goto again;
91 }
92
93 if (handle->wakeup != local_read(&rb->wakeup))
94 perf_output_wakeup(handle);
95
96out:
97 preempt_enable();
98}
99
100int perf_output_begin(struct perf_output_handle *handle,
101 struct perf_event *event, unsigned int size)
102{
103 struct ring_buffer *rb;
104 unsigned long tail, offset, head;
105 int have_lost;
106 struct perf_sample_data sample_data;
107 struct {
108 struct perf_event_header header;
109 u64 id;
110 u64 lost;
111 } lost_event;
112
113 rcu_read_lock();
114 /*
115 * For inherited events we send all the output towards the parent.
116 */
117 if (event->parent)
118 event = event->parent;
119
120 rb = rcu_dereference(event->rb);
121 if (!rb)
122 goto out;
123
124 handle->rb = rb;
125 handle->event = event;
126
127 if (!rb->nr_pages)
128 goto out;
129
130 have_lost = local_read(&rb->lost);
131 if (have_lost) {
132 lost_event.header.size = sizeof(lost_event);
133 perf_event_header__init_id(&lost_event.header, &sample_data,
134 event);
135 size += lost_event.header.size;
136 }
137
138 perf_output_get_handle(handle);
139
140 do {
141 /*
142 * Userspace could choose to issue a mb() before updating the
143 * tail pointer. So that all reads will be completed before the
144 * write is issued.
145 */
146 tail = ACCESS_ONCE(rb->user_page->data_tail);
147 smp_rmb();
148 offset = head = local_read(&rb->head);
149 head += size;
150 if (unlikely(!perf_output_space(rb, tail, offset, head)))
151 goto fail;
152 } while (local_cmpxchg(&rb->head, offset, head) != offset);
153
154 if (head - local_read(&rb->wakeup) > rb->watermark)
155 local_add(rb->watermark, &rb->wakeup);
156
157 handle->page = offset >> (PAGE_SHIFT + page_order(rb));
158 handle->page &= rb->nr_pages - 1;
159 handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1);
160 handle->addr = rb->data_pages[handle->page];
161 handle->addr += handle->size;
162 handle->size = (PAGE_SIZE << page_order(rb)) - handle->size;
163
164 if (have_lost) {
165 lost_event.header.type = PERF_RECORD_LOST;
166 lost_event.header.misc = 0;
167 lost_event.id = event->id;
168 lost_event.lost = local_xchg(&rb->lost, 0);
169
170 perf_output_put(handle, lost_event);
171 perf_event__output_id_sample(event, handle, &sample_data);
172 }
173
174 return 0;
175
176fail:
177 local_inc(&rb->lost);
178 perf_output_put_handle(handle);
179out:
180 rcu_read_unlock();
181
182 return -ENOSPC;
183}
184
185void perf_output_copy(struct perf_output_handle *handle,
186 const void *buf, unsigned int len)
187{
188 __output_copy(handle, buf, len);
189}
190
191void perf_output_end(struct perf_output_handle *handle)
192{
193 perf_output_put_handle(handle);
194 rcu_read_unlock();
195}
196
197static void
198ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
199{
200 long max_size = perf_data_size(rb);
201
202 if (watermark)
203 rb->watermark = min(max_size, watermark);
204
205 if (!rb->watermark)
206 rb->watermark = max_size / 2;
207
208 if (flags & RING_BUFFER_WRITABLE)
209 rb->writable = 1;
210
211 atomic_set(&rb->refcount, 1);
212
213 INIT_LIST_HEAD(&rb->event_list);
214 spin_lock_init(&rb->event_lock);
215}
216
217#ifndef CONFIG_PERF_USE_VMALLOC
218
219/*
220 * Back perf_mmap() with regular GFP_KERNEL-0 pages.
221 */
222
223struct page *
224perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
225{
226 if (pgoff > rb->nr_pages)
227 return NULL;
228
229 if (pgoff == 0)
230 return virt_to_page(rb->user_page);
231
232 return virt_to_page(rb->data_pages[pgoff - 1]);
233}
234
235static void *perf_mmap_alloc_page(int cpu)
236{
237 struct page *page;
238 int node;
239
240 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
241 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
242 if (!page)
243 return NULL;
244
245 return page_address(page);
246}
247
248struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
249{
250 struct ring_buffer *rb;
251 unsigned long size;
252 int i;
253
254 size = sizeof(struct ring_buffer);
255 size += nr_pages * sizeof(void *);
256
257 rb = kzalloc(size, GFP_KERNEL);
258 if (!rb)
259 goto fail;
260
261 rb->user_page = perf_mmap_alloc_page(cpu);
262 if (!rb->user_page)
263 goto fail_user_page;
264
265 for (i = 0; i < nr_pages; i++) {
266 rb->data_pages[i] = perf_mmap_alloc_page(cpu);
267 if (!rb->data_pages[i])
268 goto fail_data_pages;
269 }
270
271 rb->nr_pages = nr_pages;
272
273 ring_buffer_init(rb, watermark, flags);
274
275 return rb;
276
277fail_data_pages:
278 for (i--; i >= 0; i--)
279 free_page((unsigned long)rb->data_pages[i]);
280
281 free_page((unsigned long)rb->user_page);
282
283fail_user_page:
284 kfree(rb);
285
286fail:
287 return NULL;
288}
289
290static void perf_mmap_free_page(unsigned long addr)
291{
292 struct page *page = virt_to_page((void *)addr);
293
294 page->mapping = NULL;
295 __free_page(page);
296}
297
298void rb_free(struct ring_buffer *rb)
299{
300 int i;
301
302 perf_mmap_free_page((unsigned long)rb->user_page);
303 for (i = 0; i < rb->nr_pages; i++)
304 perf_mmap_free_page((unsigned long)rb->data_pages[i]);
305 kfree(rb);
306}
307
308#else
309
310struct page *
311perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
312{
313 if (pgoff > (1UL << page_order(rb)))
314 return NULL;
315
316 return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
317}
318
319static void perf_mmap_unmark_page(void *addr)
320{
321 struct page *page = vmalloc_to_page(addr);
322
323 page->mapping = NULL;
324}
325
326static void rb_free_work(struct work_struct *work)
327{
328 struct ring_buffer *rb;
329 void *base;
330 int i, nr;
331
332 rb = container_of(work, struct ring_buffer, work);
333 nr = 1 << page_order(rb);
334
335 base = rb->user_page;
336 for (i = 0; i < nr + 1; i++)
337 perf_mmap_unmark_page(base + (i * PAGE_SIZE));
338
339 vfree(base);
340 kfree(rb);
341}
342
343void rb_free(struct ring_buffer *rb)
344{
345 schedule_work(&rb->work);
346}
347
348struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
349{
350 struct ring_buffer *rb;
351 unsigned long size;
352 void *all_buf;
353
354 size = sizeof(struct ring_buffer);
355 size += sizeof(void *);
356
357 rb = kzalloc(size, GFP_KERNEL);
358 if (!rb)
359 goto fail;
360
361 INIT_WORK(&rb->work, rb_free_work);
362
363 all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
364 if (!all_buf)
365 goto fail_all_buf;
366
367 rb->user_page = all_buf;
368 rb->data_pages[0] = all_buf + PAGE_SIZE;
369 rb->page_order = ilog2(nr_pages);
370 rb->nr_pages = 1;
371
372 ring_buffer_init(rb, watermark, flags);
373
374 return rb;
375
376fail_all_buf:
377 kfree(rb);
378
379fail:
380 return NULL;
381}
382
383#endif
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>
7 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
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
18static bool perf_output_space(struct ring_buffer *rb, unsigned long tail,
19 unsigned long offset, unsigned long head)
20{
21 unsigned long mask;
22
23 if (!rb->writable)
24 return true;
25
26 mask = perf_data_size(rb) - 1;
27
28 offset = (offset - tail) & mask;
29 head = (head - tail) & mask;
30
31 if ((int)(head - offset) < 0)
32 return false;
33
34 return true;
35}
36
37static void perf_output_wakeup(struct perf_output_handle *handle)
38{
39 atomic_set(&handle->rb->poll, POLL_IN);
40
41 handle->event->pending_wakeup = 1;
42 irq_work_queue(&handle->event->pending);
43}
44
45/*
46 * We need to ensure a later event_id doesn't publish a head when a former
47 * event isn't done writing. However since we need to deal with NMIs we
48 * cannot fully serialize things.
49 *
50 * We only publish the head (and generate a wakeup) when the outer-most
51 * event completes.
52 */
53static void perf_output_get_handle(struct perf_output_handle *handle)
54{
55 struct ring_buffer *rb = handle->rb;
56
57 preempt_disable();
58 local_inc(&rb->nest);
59 handle->wakeup = local_read(&rb->wakeup);
60}
61
62static void perf_output_put_handle(struct perf_output_handle *handle)
63{
64 struct ring_buffer *rb = handle->rb;
65 unsigned long head;
66
67again:
68 head = local_read(&rb->head);
69
70 /*
71 * IRQ/NMI can happen here, which means we can miss a head update.
72 */
73
74 if (!local_dec_and_test(&rb->nest))
75 goto out;
76
77 /*
78 * Publish the known good head. Rely on the full barrier implied
79 * by atomic_dec_and_test() order the rb->head read and this
80 * write.
81 */
82 rb->user_page->data_head = head;
83
84 /*
85 * Now check if we missed an update, rely on the (compiler)
86 * barrier in atomic_dec_and_test() to re-read rb->head.
87 */
88 if (unlikely(head != local_read(&rb->head))) {
89 local_inc(&rb->nest);
90 goto again;
91 }
92
93 if (handle->wakeup != local_read(&rb->wakeup))
94 perf_output_wakeup(handle);
95
96out:
97 preempt_enable();
98}
99
100int perf_output_begin(struct perf_output_handle *handle,
101 struct perf_event *event, unsigned int size)
102{
103 struct ring_buffer *rb;
104 unsigned long tail, offset, head;
105 int have_lost;
106 struct perf_sample_data sample_data;
107 struct {
108 struct perf_event_header header;
109 u64 id;
110 u64 lost;
111 } lost_event;
112
113 rcu_read_lock();
114 /*
115 * For inherited events we send all the output towards the parent.
116 */
117 if (event->parent)
118 event = event->parent;
119
120 rb = rcu_dereference(event->rb);
121 if (!rb)
122 goto out;
123
124 handle->rb = rb;
125 handle->event = event;
126
127 if (!rb->nr_pages)
128 goto out;
129
130 have_lost = local_read(&rb->lost);
131 if (have_lost) {
132 lost_event.header.size = sizeof(lost_event);
133 perf_event_header__init_id(&lost_event.header, &sample_data,
134 event);
135 size += lost_event.header.size;
136 }
137
138 perf_output_get_handle(handle);
139
140 do {
141 /*
142 * Userspace could choose to issue a mb() before updating the
143 * tail pointer. So that all reads will be completed before the
144 * write is issued.
145 */
146 tail = ACCESS_ONCE(rb->user_page->data_tail);
147 smp_rmb();
148 offset = head = local_read(&rb->head);
149 head += size;
150 if (unlikely(!perf_output_space(rb, tail, offset, head)))
151 goto fail;
152 } while (local_cmpxchg(&rb->head, offset, head) != offset);
153
154 if (head - local_read(&rb->wakeup) > rb->watermark)
155 local_add(rb->watermark, &rb->wakeup);
156
157 handle->page = offset >> (PAGE_SHIFT + page_order(rb));
158 handle->page &= rb->nr_pages - 1;
159 handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1);
160 handle->addr = rb->data_pages[handle->page];
161 handle->addr += handle->size;
162 handle->size = (PAGE_SIZE << page_order(rb)) - handle->size;
163
164 if (have_lost) {
165 lost_event.header.type = PERF_RECORD_LOST;
166 lost_event.header.misc = 0;
167 lost_event.id = event->id;
168 lost_event.lost = local_xchg(&rb->lost, 0);
169
170 perf_output_put(handle, lost_event);
171 perf_event__output_id_sample(event, handle, &sample_data);
172 }
173
174 return 0;
175
176fail:
177 local_inc(&rb->lost);
178 perf_output_put_handle(handle);
179out:
180 rcu_read_unlock();
181
182 return -ENOSPC;
183}
184
185void perf_output_copy(struct perf_output_handle *handle,
186 const void *buf, unsigned int len)
187{
188 __output_copy(handle, buf, len);
189}
190
191void perf_output_end(struct perf_output_handle *handle)
192{
193 perf_output_put_handle(handle);
194 rcu_read_unlock();
195}
196
197static void
198ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
199{
200 long max_size = perf_data_size(rb);
201
202 if (watermark)
203 rb->watermark = min(max_size, watermark);
204
205 if (!rb->watermark)
206 rb->watermark = max_size / 2;
207
208 if (flags & RING_BUFFER_WRITABLE)
209 rb->writable = 1;
210
211 atomic_set(&rb->refcount, 1);
212}
213
214#ifndef CONFIG_PERF_USE_VMALLOC
215
216/*
217 * Back perf_mmap() with regular GFP_KERNEL-0 pages.
218 */
219
220struct page *
221perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
222{
223 if (pgoff > rb->nr_pages)
224 return NULL;
225
226 if (pgoff == 0)
227 return virt_to_page(rb->user_page);
228
229 return virt_to_page(rb->data_pages[pgoff - 1]);
230}
231
232static void *perf_mmap_alloc_page(int cpu)
233{
234 struct page *page;
235 int node;
236
237 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
238 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
239 if (!page)
240 return NULL;
241
242 return page_address(page);
243}
244
245struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
246{
247 struct ring_buffer *rb;
248 unsigned long size;
249 int i;
250
251 size = sizeof(struct ring_buffer);
252 size += nr_pages * sizeof(void *);
253
254 rb = kzalloc(size, GFP_KERNEL);
255 if (!rb)
256 goto fail;
257
258 rb->user_page = perf_mmap_alloc_page(cpu);
259 if (!rb->user_page)
260 goto fail_user_page;
261
262 for (i = 0; i < nr_pages; i++) {
263 rb->data_pages[i] = perf_mmap_alloc_page(cpu);
264 if (!rb->data_pages[i])
265 goto fail_data_pages;
266 }
267
268 rb->nr_pages = nr_pages;
269
270 ring_buffer_init(rb, watermark, flags);
271
272 return rb;
273
274fail_data_pages:
275 for (i--; i >= 0; i--)
276 free_page((unsigned long)rb->data_pages[i]);
277
278 free_page((unsigned long)rb->user_page);
279
280fail_user_page:
281 kfree(rb);
282
283fail:
284 return NULL;
285}
286
287static void perf_mmap_free_page(unsigned long addr)
288{
289 struct page *page = virt_to_page((void *)addr);
290
291 page->mapping = NULL;
292 __free_page(page);
293}
294
295void rb_free(struct ring_buffer *rb)
296{
297 int i;
298
299 perf_mmap_free_page((unsigned long)rb->user_page);
300 for (i = 0; i < rb->nr_pages; i++)
301 perf_mmap_free_page((unsigned long)rb->data_pages[i]);
302 kfree(rb);
303}
304
305#else
306
307struct page *
308perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
309{
310 if (pgoff > (1UL << page_order(rb)))
311 return NULL;
312
313 return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
314}
315
316static void perf_mmap_unmark_page(void *addr)
317{
318 struct page *page = vmalloc_to_page(addr);
319
320 page->mapping = NULL;
321}
322
323static void rb_free_work(struct work_struct *work)
324{
325 struct ring_buffer *rb;
326 void *base;
327 int i, nr;
328
329 rb = container_of(work, struct ring_buffer, work);
330 nr = 1 << page_order(rb);
331
332 base = rb->user_page;
333 for (i = 0; i < nr + 1; i++)
334 perf_mmap_unmark_page(base + (i * PAGE_SIZE));
335
336 vfree(base);
337 kfree(rb);
338}
339
340void rb_free(struct ring_buffer *rb)
341{
342 schedule_work(&rb->work);
343}
344
345struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
346{
347 struct ring_buffer *rb;
348 unsigned long size;
349 void *all_buf;
350
351 size = sizeof(struct ring_buffer);
352 size += sizeof(void *);
353
354 rb = kzalloc(size, GFP_KERNEL);
355 if (!rb)
356 goto fail;
357
358 INIT_WORK(&rb->work, rb_free_work);
359
360 all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
361 if (!all_buf)
362 goto fail_all_buf;
363
364 rb->user_page = all_buf;
365 rb->data_pages[0] = all_buf + PAGE_SIZE;
366 rb->page_order = ilog2(nr_pages);
367 rb->nr_pages = 1;
368
369 ring_buffer_init(rb, watermark, flags);
370
371 return rb;
372
373fail_all_buf:
374 kfree(rb);
375
376fail:
377 return NULL;
378}
379
380#endif