perf: Remove the nmi parameter from the swevent and overflow interface
[linux-2.6.git] / kernel / events / ring_buffer.c
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
18 static 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
37 static 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  */
53 static 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
62 static void perf_output_put_handle(struct perf_output_handle *handle)
63 {
64         struct ring_buffer *rb = handle->rb;
65         unsigned long head;
66
67 again:
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
96 out:
97         preempt_enable();
98 }
99
100 int perf_output_begin(struct perf_output_handle *handle,
101                       struct perf_event *event, unsigned int size,
102                       int sample)
103 {
104         struct ring_buffer *rb;
105         unsigned long tail, offset, head;
106         int have_lost;
107         struct perf_sample_data sample_data;
108         struct {
109                 struct perf_event_header header;
110                 u64                      id;
111                 u64                      lost;
112         } lost_event;
113
114         rcu_read_lock();
115         /*
116          * For inherited events we send all the output towards the parent.
117          */
118         if (event->parent)
119                 event = event->parent;
120
121         rb = rcu_dereference(event->rb);
122         if (!rb)
123                 goto out;
124
125         handle->rb      = rb;
126         handle->event   = event;
127         handle->sample  = sample;
128
129         if (!rb->nr_pages)
130                 goto out;
131
132         have_lost = local_read(&rb->lost);
133         if (have_lost) {
134                 lost_event.header.size = sizeof(lost_event);
135                 perf_event_header__init_id(&lost_event.header, &sample_data,
136                                            event);
137                 size += lost_event.header.size;
138         }
139
140         perf_output_get_handle(handle);
141
142         do {
143                 /*
144                  * Userspace could choose to issue a mb() before updating the
145                  * tail pointer. So that all reads will be completed before the
146                  * write is issued.
147                  */
148                 tail = ACCESS_ONCE(rb->user_page->data_tail);
149                 smp_rmb();
150                 offset = head = local_read(&rb->head);
151                 head += size;
152                 if (unlikely(!perf_output_space(rb, tail, offset, head)))
153                         goto fail;
154         } while (local_cmpxchg(&rb->head, offset, head) != offset);
155
156         if (head - local_read(&rb->wakeup) > rb->watermark)
157                 local_add(rb->watermark, &rb->wakeup);
158
159         handle->page = offset >> (PAGE_SHIFT + page_order(rb));
160         handle->page &= rb->nr_pages - 1;
161         handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1);
162         handle->addr = rb->data_pages[handle->page];
163         handle->addr += handle->size;
164         handle->size = (PAGE_SIZE << page_order(rb)) - handle->size;
165
166         if (have_lost) {
167                 lost_event.header.type = PERF_RECORD_LOST;
168                 lost_event.header.misc = 0;
169                 lost_event.id          = event->id;
170                 lost_event.lost        = local_xchg(&rb->lost, 0);
171
172                 perf_output_put(handle, lost_event);
173                 perf_event__output_id_sample(event, handle, &sample_data);
174         }
175
176         return 0;
177
178 fail:
179         local_inc(&rb->lost);
180         perf_output_put_handle(handle);
181 out:
182         rcu_read_unlock();
183
184         return -ENOSPC;
185 }
186
187 void perf_output_copy(struct perf_output_handle *handle,
188                       const void *buf, unsigned int len)
189 {
190         __output_copy(handle, buf, len);
191 }
192
193 void perf_output_end(struct perf_output_handle *handle)
194 {
195         struct perf_event *event = handle->event;
196         struct ring_buffer *rb = handle->rb;
197
198         if (handle->sample && !event->attr.watermark) {
199                 int wakeup_events = event->attr.wakeup_events;
200
201                 if (wakeup_events) {
202                         int events = local_inc_return(&rb->events);
203                         if (events >= wakeup_events) {
204                                 local_sub(wakeup_events, &rb->events);
205                                 local_inc(&rb->wakeup);
206                         }
207                 }
208         }
209
210         perf_output_put_handle(handle);
211         rcu_read_unlock();
212 }
213
214 static void
215 ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
216 {
217         long max_size = perf_data_size(rb);
218
219         if (watermark)
220                 rb->watermark = min(max_size, watermark);
221
222         if (!rb->watermark)
223                 rb->watermark = max_size / 2;
224
225         if (flags & RING_BUFFER_WRITABLE)
226                 rb->writable = 1;
227
228         atomic_set(&rb->refcount, 1);
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
323
324 struct page *
325 perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
326 {
327         if (pgoff > (1UL << page_order(rb)))
328                 return NULL;
329
330         return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
331 }
332
333 static void perf_mmap_unmark_page(void *addr)
334 {
335         struct page *page = vmalloc_to_page(addr);
336
337         page->mapping = NULL;
338 }
339
340 static void rb_free_work(struct work_struct *work)
341 {
342         struct ring_buffer *rb;
343         void *base;
344         int i, nr;
345
346         rb = container_of(work, struct ring_buffer, work);
347         nr = 1 << page_order(rb);
348
349         base = rb->user_page;
350         for (i = 0; i < nr + 1; i++)
351                 perf_mmap_unmark_page(base + (i * PAGE_SIZE));
352
353         vfree(base);
354         kfree(rb);
355 }
356
357 void rb_free(struct ring_buffer *rb)
358 {
359         schedule_work(&rb->work);
360 }
361
362 struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
363 {
364         struct ring_buffer *rb;
365         unsigned long size;
366         void *all_buf;
367
368         size = sizeof(struct ring_buffer);
369         size += sizeof(void *);
370
371         rb = kzalloc(size, GFP_KERNEL);
372         if (!rb)
373                 goto fail;
374
375         INIT_WORK(&rb->work, rb_free_work);
376
377         all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
378         if (!all_buf)
379                 goto fail_all_buf;
380
381         rb->user_page = all_buf;
382         rb->data_pages[0] = all_buf + PAGE_SIZE;
383         rb->page_order = ilog2(nr_pages);
384         rb->nr_pages = 1;
385
386         ring_buffer_init(rb, watermark, flags);
387
388         return rb;
389
390 fail_all_buf:
391         kfree(rb);
392
393 fail:
394         return NULL;
395 }
396
397 #endif