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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#include <linux/circ_buf.h>
16
17#include "internal.h"
18
19static void perf_output_wakeup(struct perf_output_handle *handle)
20{
21 atomic_set(&handle->rb->poll, POLL_IN);
22
23 handle->event->pending_wakeup = 1;
24 irq_work_queue(&handle->event->pending);
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 */
35static 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
44static void perf_output_put_handle(struct perf_output_handle *handle)
45{
46 struct ring_buffer *rb = handle->rb;
47 unsigned long head;
48
49again:
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 /*
60 * Since the mmap() consumer (userspace) can run on a different CPU:
61 *
62 * kernel user
63 *
64 * if (LOAD ->data_tail) { LOAD ->data_head
65 * (A) smp_rmb() (C)
66 * STORE $data LOAD $data
67 * smp_wmb() (B) smp_mb() (D)
68 * STORE ->data_head STORE ->data_tail
69 * }
70 *
71 * Where A pairs with D, and B pairs with C.
72 *
73 * In our case (A) is a control dependency that separates the load of
74 * the ->data_tail and the stores of $data. In case ->data_tail
75 * indicates there is no room in the buffer to store $data we do not.
76 *
77 * D needs to be a full barrier since it separates the data READ
78 * from the tail WRITE.
79 *
80 * For B a WMB is sufficient since it separates two WRITEs, and for C
81 * an RMB is sufficient since it separates two READs.
82 *
83 * See perf_output_begin().
84 */
85 smp_wmb(); /* B, matches C */
86 rb->user_page->data_head = head;
87
88 /*
89 * Now check if we missed an update -- rely on previous implied
90 * compiler barriers to force a re-read.
91 */
92 if (unlikely(head != local_read(&rb->head))) {
93 local_inc(&rb->nest);
94 goto again;
95 }
96
97 if (handle->wakeup != local_read(&rb->wakeup))
98 perf_output_wakeup(handle);
99
100out:
101 preempt_enable();
102}
103
104int perf_output_begin(struct perf_output_handle *handle,
105 struct perf_event *event, unsigned int size)
106{
107 struct ring_buffer *rb;
108 unsigned long tail, offset, head;
109 int have_lost, page_shift;
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);
124 if (unlikely(!rb))
125 goto out;
126
127 if (unlikely(!rb->nr_pages))
128 goto out;
129
130 handle->rb = rb;
131 handle->event = event;
132
133 have_lost = local_read(&rb->lost);
134 if (unlikely(have_lost)) {
135 size += sizeof(lost_event);
136 if (event->attr.sample_id_all)
137 size += event->id_header_size;
138 }
139
140 perf_output_get_handle(handle);
141
142 do {
143 tail = ACCESS_ONCE(rb->user_page->data_tail);
144 offset = head = local_read(&rb->head);
145 if (!rb->overwrite &&
146 unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size))
147 goto fail;
148
149 /*
150 * The above forms a control dependency barrier separating the
151 * @tail load above from the data stores below. Since the @tail
152 * load is required to compute the branch to fail below.
153 *
154 * A, matches D; the full memory barrier userspace SHOULD issue
155 * after reading the data and before storing the new tail
156 * position.
157 *
158 * See perf_output_put_handle().
159 */
160
161 head += size;
162 } while (local_cmpxchg(&rb->head, offset, head) != offset);
163
164 /*
165 * We rely on the implied barrier() by local_cmpxchg() to ensure
166 * none of the data stores below can be lifted up by the compiler.
167 */
168
169 if (unlikely(head - local_read(&rb->wakeup) > rb->watermark))
170 local_add(rb->watermark, &rb->wakeup);
171
172 page_shift = PAGE_SHIFT + page_order(rb);
173
174 handle->page = (offset >> page_shift) & (rb->nr_pages - 1);
175 offset &= (1UL << page_shift) - 1;
176 handle->addr = rb->data_pages[handle->page] + offset;
177 handle->size = (1UL << page_shift) - offset;
178
179 if (unlikely(have_lost)) {
180 struct perf_sample_data sample_data;
181
182 lost_event.header.size = sizeof(lost_event);
183 lost_event.header.type = PERF_RECORD_LOST;
184 lost_event.header.misc = 0;
185 lost_event.id = event->id;
186 lost_event.lost = local_xchg(&rb->lost, 0);
187
188 perf_event_header__init_id(&lost_event.header,
189 &sample_data, event);
190 perf_output_put(handle, lost_event);
191 perf_event__output_id_sample(event, handle, &sample_data);
192 }
193
194 return 0;
195
196fail:
197 local_inc(&rb->lost);
198 perf_output_put_handle(handle);
199out:
200 rcu_read_unlock();
201
202 return -ENOSPC;
203}
204
205unsigned int perf_output_copy(struct perf_output_handle *handle,
206 const void *buf, unsigned int len)
207{
208 return __output_copy(handle, buf, len);
209}
210
211unsigned int perf_output_skip(struct perf_output_handle *handle,
212 unsigned int len)
213{
214 return __output_skip(handle, NULL, len);
215}
216
217void perf_output_end(struct perf_output_handle *handle)
218{
219 perf_output_put_handle(handle);
220 rcu_read_unlock();
221}
222
223static void
224ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
225{
226 long max_size = perf_data_size(rb);
227
228 if (watermark)
229 rb->watermark = min(max_size, watermark);
230
231 if (!rb->watermark)
232 rb->watermark = max_size / 2;
233
234 if (flags & RING_BUFFER_WRITABLE)
235 rb->overwrite = 0;
236 else
237 rb->overwrite = 1;
238
239 atomic_set(&rb->refcount, 1);
240
241 INIT_LIST_HEAD(&rb->event_list);
242 spin_lock_init(&rb->event_lock);
243}
244
245#ifndef CONFIG_PERF_USE_VMALLOC
246
247/*
248 * Back perf_mmap() with regular GFP_KERNEL-0 pages.
249 */
250
251struct page *
252perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
253{
254 if (pgoff > rb->nr_pages)
255 return NULL;
256
257 if (pgoff == 0)
258 return virt_to_page(rb->user_page);
259
260 return virt_to_page(rb->data_pages[pgoff - 1]);
261}
262
263static void *perf_mmap_alloc_page(int cpu)
264{
265 struct page *page;
266 int node;
267
268 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
269 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
270 if (!page)
271 return NULL;
272
273 return page_address(page);
274}
275
276struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
277{
278 struct ring_buffer *rb;
279 unsigned long size;
280 int i;
281
282 size = sizeof(struct ring_buffer);
283 size += nr_pages * sizeof(void *);
284
285 rb = kzalloc(size, GFP_KERNEL);
286 if (!rb)
287 goto fail;
288
289 rb->user_page = perf_mmap_alloc_page(cpu);
290 if (!rb->user_page)
291 goto fail_user_page;
292
293 for (i = 0; i < nr_pages; i++) {
294 rb->data_pages[i] = perf_mmap_alloc_page(cpu);
295 if (!rb->data_pages[i])
296 goto fail_data_pages;
297 }
298
299 rb->nr_pages = nr_pages;
300
301 ring_buffer_init(rb, watermark, flags);
302
303 return rb;
304
305fail_data_pages:
306 for (i--; i >= 0; i--)
307 free_page((unsigned long)rb->data_pages[i]);
308
309 free_page((unsigned long)rb->user_page);
310
311fail_user_page:
312 kfree(rb);
313
314fail:
315 return NULL;
316}
317
318static void perf_mmap_free_page(unsigned long addr)
319{
320 struct page *page = virt_to_page((void *)addr);
321
322 page->mapping = NULL;
323 __free_page(page);
324}
325
326void rb_free(struct ring_buffer *rb)
327{
328 int i;
329
330 perf_mmap_free_page((unsigned long)rb->user_page);
331 for (i = 0; i < rb->nr_pages; i++)
332 perf_mmap_free_page((unsigned long)rb->data_pages[i]);
333 kfree(rb);
334}
335
336#else
337static int data_page_nr(struct ring_buffer *rb)
338{
339 return rb->nr_pages << page_order(rb);
340}
341
342struct page *
343perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
344{
345 /* The '>' counts in the user page. */
346 if (pgoff > data_page_nr(rb))
347 return NULL;
348
349 return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
350}
351
352static void perf_mmap_unmark_page(void *addr)
353{
354 struct page *page = vmalloc_to_page(addr);
355
356 page->mapping = NULL;
357}
358
359static void rb_free_work(struct work_struct *work)
360{
361 struct ring_buffer *rb;
362 void *base;
363 int i, nr;
364
365 rb = container_of(work, struct ring_buffer, work);
366 nr = data_page_nr(rb);
367
368 base = rb->user_page;
369 /* The '<=' counts in the user page. */
370 for (i = 0; i <= nr; i++)
371 perf_mmap_unmark_page(base + (i * PAGE_SIZE));
372
373 vfree(base);
374 kfree(rb);
375}
376
377void rb_free(struct ring_buffer *rb)
378{
379 schedule_work(&rb->work);
380}
381
382struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
383{
384 struct ring_buffer *rb;
385 unsigned long size;
386 void *all_buf;
387
388 size = sizeof(struct ring_buffer);
389 size += sizeof(void *);
390
391 rb = kzalloc(size, GFP_KERNEL);
392 if (!rb)
393 goto fail;
394
395 INIT_WORK(&rb->work, rb_free_work);
396
397 all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
398 if (!all_buf)
399 goto fail_all_buf;
400
401 rb->user_page = all_buf;
402 rb->data_pages[0] = all_buf + PAGE_SIZE;
403 rb->page_order = ilog2(nr_pages);
404 rb->nr_pages = !!nr_pages;
405
406 ring_buffer_init(rb, watermark, flags);
407
408 return rb;
409
410fail_all_buf:
411 kfree(rb);
412
413fail:
414 return NULL;
415}
416
417#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