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852c2936 MD |
1 | /* |
2 | * ring_buffer_frontend.c | |
3 | * | |
4 | * (C) Copyright 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
5 | * | |
6 | * Ring buffer wait-free buffer synchronization. Producer-consumer and flight | |
7 | * recorder (overwrite) modes. See thesis: | |
8 | * | |
9 | * Desnoyers, Mathieu (2009), "Low-Impact Operating System Tracing", Ph.D. | |
10 | * dissertation, Ecole Polytechnique de Montreal. | |
11 | * http://www.lttng.org/pub/thesis/desnoyers-dissertation-2009-12.pdf | |
12 | * | |
13 | * - Algorithm presentation in Chapter 5: | |
14 | * "Lockless Multi-Core High-Throughput Buffering". | |
15 | * - Algorithm formal verification in Section 8.6: | |
16 | * "Formal verification of LTTng" | |
17 | * | |
18 | * Author: | |
19 | * Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
20 | * | |
21 | * Inspired from LTT and RelayFS: | |
22 | * Karim Yaghmour <karim@opersys.com> | |
23 | * Tom Zanussi <zanussi@us.ibm.com> | |
24 | * Bob Wisniewski <bob@watson.ibm.com> | |
25 | * And from K42 : | |
26 | * Bob Wisniewski <bob@watson.ibm.com> | |
27 | * | |
28 | * Buffer reader semantic : | |
29 | * | |
30 | * - get_subbuf_size | |
31 | * while buffer is not finalized and empty | |
32 | * - get_subbuf | |
33 | * - if return value != 0, continue | |
34 | * - splice one subbuffer worth of data to a pipe | |
35 | * - splice the data from pipe to disk/network | |
36 | * - put_subbuf | |
37 | * | |
38 | * Dual LGPL v2.1/GPL v2 license. | |
39 | */ | |
40 | ||
4931a13e MD |
41 | #include "config.h" |
42 | #include "backend.h" | |
43 | #include "frontend.h" | |
44 | #include "iterator.h" | |
45 | #include "nohz.h" | |
852c2936 MD |
46 | |
47 | /* | |
48 | * Internal structure representing offsets to use at a sub-buffer switch. | |
49 | */ | |
50 | struct switch_offsets { | |
51 | unsigned long begin, end, old; | |
52 | size_t pre_header_padding, size; | |
53 | unsigned int switch_new_start:1, switch_new_end:1, switch_old_start:1, | |
54 | switch_old_end:1; | |
55 | }; | |
56 | ||
57 | #ifdef CONFIG_NO_HZ | |
58 | enum tick_nohz_val { | |
59 | TICK_NOHZ_STOP, | |
60 | TICK_NOHZ_FLUSH, | |
61 | TICK_NOHZ_RESTART, | |
62 | }; | |
63 | ||
64 | static ATOMIC_NOTIFIER_HEAD(tick_nohz_notifier); | |
65 | #endif /* CONFIG_NO_HZ */ | |
66 | ||
67 | static DEFINE_PER_CPU(spinlock_t, ring_buffer_nohz_lock); | |
68 | ||
69 | DEFINE_PER_CPU(unsigned int, lib_ring_buffer_nesting); | |
70 | EXPORT_PER_CPU_SYMBOL(lib_ring_buffer_nesting); | |
71 | ||
72 | static | |
73 | void lib_ring_buffer_print_errors(struct channel *chan, | |
74 | struct lib_ring_buffer *buf, int cpu); | |
75 | ||
76 | /* | |
77 | * Must be called under cpu hotplug protection. | |
78 | */ | |
79 | void lib_ring_buffer_free(struct lib_ring_buffer *buf) | |
80 | { | |
81 | struct channel *chan = buf->backend.chan; | |
82 | ||
83 | lib_ring_buffer_print_errors(chan, buf, buf->backend.cpu); | |
84 | kfree(buf->commit_hot); | |
85 | kfree(buf->commit_cold); | |
86 | ||
87 | lib_ring_buffer_backend_free(&buf->backend); | |
88 | } | |
89 | ||
90 | /** | |
91 | * lib_ring_buffer_reset - Reset ring buffer to initial values. | |
92 | * @buf: Ring buffer. | |
93 | * | |
94 | * Effectively empty the ring buffer. Should be called when the buffer is not | |
95 | * used for writing. The ring buffer can be opened for reading, but the reader | |
96 | * should not be using the iterator concurrently with reset. The previous | |
97 | * current iterator record is reset. | |
98 | */ | |
99 | void lib_ring_buffer_reset(struct lib_ring_buffer *buf) | |
100 | { | |
101 | struct channel *chan = buf->backend.chan; | |
102 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
103 | unsigned int i; | |
104 | ||
105 | /* | |
106 | * Reset iterator first. It will put the subbuffer if it currently holds | |
107 | * it. | |
108 | */ | |
109 | lib_ring_buffer_iterator_reset(buf); | |
110 | v_set(config, &buf->offset, 0); | |
111 | for (i = 0; i < chan->backend.num_subbuf; i++) { | |
112 | v_set(config, &buf->commit_hot[i].cc, 0); | |
113 | v_set(config, &buf->commit_hot[i].seq, 0); | |
114 | v_set(config, &buf->commit_cold[i].cc_sb, 0); | |
115 | } | |
116 | atomic_long_set(&buf->consumed, 0); | |
117 | atomic_set(&buf->record_disabled, 0); | |
118 | v_set(config, &buf->last_tsc, 0); | |
119 | lib_ring_buffer_backend_reset(&buf->backend); | |
120 | /* Don't reset number of active readers */ | |
121 | v_set(config, &buf->records_lost_full, 0); | |
122 | v_set(config, &buf->records_lost_wrap, 0); | |
123 | v_set(config, &buf->records_lost_big, 0); | |
124 | v_set(config, &buf->records_count, 0); | |
125 | v_set(config, &buf->records_overrun, 0); | |
126 | buf->finalized = 0; | |
127 | } | |
128 | EXPORT_SYMBOL_GPL(lib_ring_buffer_reset); | |
129 | ||
130 | /** | |
131 | * channel_reset - Reset channel to initial values. | |
132 | * @chan: Channel. | |
133 | * | |
134 | * Effectively empty the channel. Should be called when the channel is not used | |
135 | * for writing. The channel can be opened for reading, but the reader should not | |
136 | * be using the iterator concurrently with reset. The previous current iterator | |
137 | * record is reset. | |
138 | */ | |
139 | void channel_reset(struct channel *chan) | |
140 | { | |
141 | /* | |
142 | * Reset iterators first. Will put the subbuffer if held for reading. | |
143 | */ | |
144 | channel_iterator_reset(chan); | |
145 | atomic_set(&chan->record_disabled, 0); | |
146 | /* Don't reset commit_count_mask, still valid */ | |
147 | channel_backend_reset(&chan->backend); | |
148 | /* Don't reset switch/read timer interval */ | |
149 | /* Don't reset notifiers and notifier enable bits */ | |
150 | /* Don't reset reader reference count */ | |
151 | } | |
152 | EXPORT_SYMBOL_GPL(channel_reset); | |
153 | ||
154 | /* | |
155 | * Must be called under cpu hotplug protection. | |
156 | */ | |
157 | int lib_ring_buffer_create(struct lib_ring_buffer *buf, | |
158 | struct channel_backend *chanb, int cpu) | |
159 | { | |
160 | const struct lib_ring_buffer_config *config = chanb->config; | |
161 | struct channel *chan = container_of(chanb, struct channel, backend); | |
162 | void *priv = chanb->priv; | |
163 | unsigned int num_subbuf; | |
164 | size_t subbuf_header_size; | |
165 | u64 tsc; | |
166 | int ret; | |
167 | ||
168 | /* Test for cpu hotplug */ | |
169 | if (buf->backend.allocated) | |
170 | return 0; | |
171 | ||
172 | /* | |
173 | * Paranoia: per cpu dynamic allocation is not officially documented as | |
174 | * zeroing the memory, so let's do it here too, just in case. | |
175 | */ | |
176 | memset(buf, 0, sizeof(*buf)); | |
177 | ||
178 | ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend, cpu); | |
179 | if (ret) | |
180 | return ret; | |
181 | ||
182 | buf->commit_hot = | |
183 | kzalloc_node(ALIGN(sizeof(*buf->commit_hot) | |
184 | * chan->backend.num_subbuf, | |
185 | 1 << INTERNODE_CACHE_SHIFT), | |
186 | GFP_KERNEL, cpu_to_node(max(cpu, 0))); | |
187 | if (!buf->commit_hot) { | |
188 | ret = -ENOMEM; | |
189 | goto free_chanbuf; | |
190 | } | |
191 | ||
192 | buf->commit_cold = | |
193 | kzalloc_node(ALIGN(sizeof(*buf->commit_cold) | |
194 | * chan->backend.num_subbuf, | |
195 | 1 << INTERNODE_CACHE_SHIFT), | |
196 | GFP_KERNEL, cpu_to_node(max(cpu, 0))); | |
197 | if (!buf->commit_cold) { | |
198 | ret = -ENOMEM; | |
199 | goto free_commit; | |
200 | } | |
201 | ||
202 | num_subbuf = chan->backend.num_subbuf; | |
203 | init_waitqueue_head(&buf->read_wait); | |
204 | raw_spin_lock_init(&buf->raw_tick_nohz_spinlock); | |
205 | ||
206 | /* | |
207 | * Write the subbuffer header for first subbuffer so we know the total | |
208 | * duration of data gathering. | |
209 | */ | |
210 | subbuf_header_size = config->cb.subbuffer_header_size(); | |
211 | v_set(config, &buf->offset, subbuf_header_size); | |
212 | subbuffer_id_clear_noref(config, &buf->backend.buf_wsb[0].id); | |
213 | tsc = config->cb.ring_buffer_clock_read(buf->backend.chan); | |
214 | config->cb.buffer_begin(buf, tsc, 0); | |
215 | v_add(config, subbuf_header_size, &buf->commit_hot[0].cc); | |
216 | ||
217 | if (config->cb.buffer_create) { | |
218 | ret = config->cb.buffer_create(buf, priv, cpu, chanb->name); | |
219 | if (ret) | |
220 | goto free_init; | |
221 | } | |
222 | ||
223 | /* | |
224 | * Ensure the buffer is ready before setting it to allocated and setting | |
225 | * the cpumask. | |
226 | * Used for cpu hotplug vs cpumask iteration. | |
227 | */ | |
228 | smp_wmb(); | |
229 | buf->backend.allocated = 1; | |
230 | ||
231 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { | |
232 | CHAN_WARN_ON(chan, cpumask_test_cpu(cpu, | |
233 | chan->backend.cpumask)); | |
234 | cpumask_set_cpu(cpu, chan->backend.cpumask); | |
235 | } | |
236 | ||
237 | return 0; | |
238 | ||
239 | /* Error handling */ | |
240 | free_init: | |
241 | kfree(buf->commit_cold); | |
242 | free_commit: | |
243 | kfree(buf->commit_hot); | |
244 | free_chanbuf: | |
245 | lib_ring_buffer_backend_free(&buf->backend); | |
246 | return ret; | |
247 | } | |
248 | ||
249 | static void switch_buffer_timer(unsigned long data) | |
250 | { | |
251 | struct lib_ring_buffer *buf = (struct lib_ring_buffer *)data; | |
252 | struct channel *chan = buf->backend.chan; | |
253 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
254 | ||
255 | /* | |
256 | * Only flush buffers periodically if readers are active. | |
257 | */ | |
258 | if (atomic_long_read(&buf->active_readers)) | |
259 | lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE); | |
260 | ||
261 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) | |
262 | mod_timer_pinned(&buf->switch_timer, | |
263 | jiffies + chan->switch_timer_interval); | |
264 | else | |
265 | mod_timer(&buf->switch_timer, | |
266 | jiffies + chan->switch_timer_interval); | |
267 | } | |
268 | ||
269 | /* | |
270 | * Called with ring_buffer_nohz_lock held for per-cpu buffers. | |
271 | */ | |
272 | static void lib_ring_buffer_start_switch_timer(struct lib_ring_buffer *buf) | |
273 | { | |
274 | struct channel *chan = buf->backend.chan; | |
275 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
276 | ||
277 | if (!chan->switch_timer_interval || buf->switch_timer_enabled) | |
278 | return; | |
279 | init_timer(&buf->switch_timer); | |
280 | buf->switch_timer.function = switch_buffer_timer; | |
281 | buf->switch_timer.expires = jiffies + chan->switch_timer_interval; | |
282 | buf->switch_timer.data = (unsigned long)buf; | |
283 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) | |
284 | add_timer_on(&buf->switch_timer, buf->backend.cpu); | |
285 | else | |
286 | add_timer(&buf->switch_timer); | |
287 | buf->switch_timer_enabled = 1; | |
288 | } | |
289 | ||
290 | /* | |
291 | * Called with ring_buffer_nohz_lock held for per-cpu buffers. | |
292 | */ | |
293 | static void lib_ring_buffer_stop_switch_timer(struct lib_ring_buffer *buf) | |
294 | { | |
295 | struct channel *chan = buf->backend.chan; | |
296 | ||
297 | if (!chan->switch_timer_interval || !buf->switch_timer_enabled) | |
298 | return; | |
299 | ||
300 | del_timer_sync(&buf->switch_timer); | |
301 | buf->switch_timer_enabled = 0; | |
302 | } | |
303 | ||
304 | /* | |
305 | * Polling timer to check the channels for data. | |
306 | */ | |
307 | static void read_buffer_timer(unsigned long data) | |
308 | { | |
309 | struct lib_ring_buffer *buf = (struct lib_ring_buffer *)data; | |
310 | struct channel *chan = buf->backend.chan; | |
311 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
312 | ||
313 | CHAN_WARN_ON(chan, !buf->backend.allocated); | |
314 | ||
315 | if (atomic_long_read(&buf->active_readers) | |
316 | && lib_ring_buffer_poll_deliver(config, buf, chan)) { | |
317 | wake_up_interruptible(&buf->read_wait); | |
318 | wake_up_interruptible(&chan->read_wait); | |
319 | } | |
320 | ||
321 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) | |
322 | mod_timer_pinned(&buf->read_timer, | |
323 | jiffies + chan->read_timer_interval); | |
324 | else | |
325 | mod_timer(&buf->read_timer, | |
326 | jiffies + chan->read_timer_interval); | |
327 | } | |
328 | ||
329 | /* | |
330 | * Called with ring_buffer_nohz_lock held for per-cpu buffers. | |
331 | */ | |
332 | static void lib_ring_buffer_start_read_timer(struct lib_ring_buffer *buf) | |
333 | { | |
334 | struct channel *chan = buf->backend.chan; | |
335 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
336 | ||
337 | if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER | |
338 | || !chan->read_timer_interval | |
339 | || buf->read_timer_enabled) | |
340 | return; | |
341 | ||
342 | init_timer(&buf->read_timer); | |
343 | buf->read_timer.function = read_buffer_timer; | |
344 | buf->read_timer.expires = jiffies + chan->read_timer_interval; | |
345 | buf->read_timer.data = (unsigned long)buf; | |
346 | ||
347 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) | |
348 | add_timer_on(&buf->read_timer, buf->backend.cpu); | |
349 | else | |
350 | add_timer(&buf->read_timer); | |
351 | buf->read_timer_enabled = 1; | |
352 | } | |
353 | ||
354 | /* | |
355 | * Called with ring_buffer_nohz_lock held for per-cpu buffers. | |
356 | */ | |
357 | static void lib_ring_buffer_stop_read_timer(struct lib_ring_buffer *buf) | |
358 | { | |
359 | struct channel *chan = buf->backend.chan; | |
360 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
361 | ||
362 | if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER | |
363 | || !chan->read_timer_interval | |
364 | || !buf->read_timer_enabled) | |
365 | return; | |
366 | ||
367 | del_timer_sync(&buf->read_timer); | |
368 | /* | |
369 | * do one more check to catch data that has been written in the last | |
370 | * timer period. | |
371 | */ | |
372 | if (lib_ring_buffer_poll_deliver(config, buf, chan)) { | |
373 | wake_up_interruptible(&buf->read_wait); | |
374 | wake_up_interruptible(&chan->read_wait); | |
375 | } | |
376 | buf->read_timer_enabled = 0; | |
377 | } | |
378 | ||
379 | #ifdef CONFIG_HOTPLUG_CPU | |
380 | /** | |
381 | * lib_ring_buffer_cpu_hp_callback - CPU hotplug callback | |
382 | * @nb: notifier block | |
383 | * @action: hotplug action to take | |
384 | * @hcpu: CPU number | |
385 | * | |
386 | * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD) | |
387 | */ | |
388 | static | |
389 | int __cpuinit lib_ring_buffer_cpu_hp_callback(struct notifier_block *nb, | |
390 | unsigned long action, | |
391 | void *hcpu) | |
392 | { | |
393 | unsigned int cpu = (unsigned long)hcpu; | |
394 | struct channel *chan = container_of(nb, struct channel, | |
395 | cpu_hp_notifier); | |
396 | struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, cpu); | |
397 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
398 | ||
399 | if (!chan->cpu_hp_enable) | |
400 | return NOTIFY_DONE; | |
401 | ||
402 | CHAN_WARN_ON(chan, config->alloc == RING_BUFFER_ALLOC_GLOBAL); | |
403 | ||
404 | switch (action) { | |
405 | case CPU_DOWN_FAILED: | |
406 | case CPU_DOWN_FAILED_FROZEN: | |
407 | case CPU_ONLINE: | |
408 | case CPU_ONLINE_FROZEN: | |
409 | wake_up_interruptible(&chan->hp_wait); | |
410 | lib_ring_buffer_start_switch_timer(buf); | |
411 | lib_ring_buffer_start_read_timer(buf); | |
412 | return NOTIFY_OK; | |
413 | ||
414 | case CPU_DOWN_PREPARE: | |
415 | case CPU_DOWN_PREPARE_FROZEN: | |
416 | lib_ring_buffer_stop_switch_timer(buf); | |
417 | lib_ring_buffer_stop_read_timer(buf); | |
418 | return NOTIFY_OK; | |
419 | ||
420 | case CPU_DEAD: | |
421 | case CPU_DEAD_FROZEN: | |
422 | /* | |
423 | * Performing a buffer switch on a remote CPU. Performed by | |
424 | * the CPU responsible for doing the hotunplug after the target | |
425 | * CPU stopped running completely. Ensures that all data | |
426 | * from that remote CPU is flushed. | |
427 | */ | |
428 | lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE); | |
429 | return NOTIFY_OK; | |
430 | ||
431 | default: | |
432 | return NOTIFY_DONE; | |
433 | } | |
434 | } | |
435 | #endif | |
436 | ||
437 | #if defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER) | |
438 | /* | |
439 | * For per-cpu buffers, call the reader wakeups before switching the buffer, so | |
440 | * that wake-up-tracing generated events are flushed before going idle (in | |
441 | * tick_nohz). We test if the spinlock is locked to deal with the race where | |
442 | * readers try to sample the ring buffer before we perform the switch. We let | |
443 | * the readers retry in that case. If there is data in the buffer, the wake up | |
444 | * is going to forbid the CPU running the reader thread from going idle. | |
445 | */ | |
446 | static int notrace ring_buffer_tick_nohz_callback(struct notifier_block *nb, | |
447 | unsigned long val, | |
448 | void *data) | |
449 | { | |
450 | struct channel *chan = container_of(nb, struct channel, | |
451 | tick_nohz_notifier); | |
452 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
453 | struct lib_ring_buffer *buf; | |
454 | int cpu = smp_processor_id(); | |
455 | ||
456 | if (config->alloc != RING_BUFFER_ALLOC_PER_CPU) { | |
457 | /* | |
458 | * We don't support keeping the system idle with global buffers | |
459 | * and streaming active. In order to do so, we would need to | |
460 | * sample a non-nohz-cpumask racelessly with the nohz updates | |
461 | * without adding synchronization overhead to nohz. Leave this | |
462 | * use-case out for now. | |
463 | */ | |
464 | return 0; | |
465 | } | |
466 | ||
467 | buf = channel_get_ring_buffer(config, chan, cpu); | |
468 | switch (val) { | |
469 | case TICK_NOHZ_FLUSH: | |
470 | raw_spin_lock(&buf->raw_tick_nohz_spinlock); | |
471 | if (config->wakeup == RING_BUFFER_WAKEUP_BY_TIMER | |
472 | && chan->read_timer_interval | |
473 | && atomic_long_read(&buf->active_readers) | |
474 | && (lib_ring_buffer_poll_deliver(config, buf, chan) | |
475 | || lib_ring_buffer_pending_data(config, buf, chan))) { | |
476 | wake_up_interruptible(&buf->read_wait); | |
477 | wake_up_interruptible(&chan->read_wait); | |
478 | } | |
479 | if (chan->switch_timer_interval) | |
480 | lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE); | |
481 | raw_spin_unlock(&buf->raw_tick_nohz_spinlock); | |
482 | break; | |
483 | case TICK_NOHZ_STOP: | |
484 | spin_lock(&__get_cpu_var(ring_buffer_nohz_lock)); | |
485 | lib_ring_buffer_stop_switch_timer(buf); | |
486 | lib_ring_buffer_stop_read_timer(buf); | |
487 | spin_unlock(&__get_cpu_var(ring_buffer_nohz_lock)); | |
488 | break; | |
489 | case TICK_NOHZ_RESTART: | |
490 | spin_lock(&__get_cpu_var(ring_buffer_nohz_lock)); | |
491 | lib_ring_buffer_start_read_timer(buf); | |
492 | lib_ring_buffer_start_switch_timer(buf); | |
493 | spin_unlock(&__get_cpu_var(ring_buffer_nohz_lock)); | |
494 | break; | |
495 | } | |
496 | ||
497 | return 0; | |
498 | } | |
499 | ||
500 | void notrace lib_ring_buffer_tick_nohz_flush(void) | |
501 | { | |
502 | atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_FLUSH, | |
503 | NULL); | |
504 | } | |
505 | ||
506 | void notrace lib_ring_buffer_tick_nohz_stop(void) | |
507 | { | |
508 | atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_STOP, | |
509 | NULL); | |
510 | } | |
511 | ||
512 | void notrace lib_ring_buffer_tick_nohz_restart(void) | |
513 | { | |
514 | atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_RESTART, | |
515 | NULL); | |
516 | } | |
517 | #endif /* defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER) */ | |
518 | ||
519 | /* | |
520 | * Holds CPU hotplug. | |
521 | */ | |
522 | static void channel_unregister_notifiers(struct channel *chan) | |
523 | { | |
524 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
525 | int cpu; | |
526 | ||
527 | channel_iterator_unregister_notifiers(chan); | |
528 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { | |
529 | #ifdef CONFIG_NO_HZ | |
530 | /* | |
531 | * Remove the nohz notifier first, so we are certain we stop | |
532 | * the timers. | |
533 | */ | |
534 | atomic_notifier_chain_unregister(&tick_nohz_notifier, | |
535 | &chan->tick_nohz_notifier); | |
536 | /* | |
537 | * ring_buffer_nohz_lock will not be needed below, because | |
538 | * we just removed the notifiers, which were the only source of | |
539 | * concurrency. | |
540 | */ | |
541 | #endif /* CONFIG_NO_HZ */ | |
542 | #ifdef CONFIG_HOTPLUG_CPU | |
543 | get_online_cpus(); | |
544 | chan->cpu_hp_enable = 0; | |
545 | for_each_online_cpu(cpu) { | |
546 | struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, | |
547 | cpu); | |
548 | lib_ring_buffer_stop_switch_timer(buf); | |
549 | lib_ring_buffer_stop_read_timer(buf); | |
550 | } | |
551 | put_online_cpus(); | |
552 | unregister_cpu_notifier(&chan->cpu_hp_notifier); | |
553 | #else | |
554 | for_each_possible_cpu(cpu) { | |
555 | struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, | |
556 | cpu); | |
557 | lib_ring_buffer_stop_switch_timer(buf); | |
558 | lib_ring_buffer_stop_read_timer(buf); | |
559 | } | |
560 | #endif | |
561 | } else { | |
562 | struct lib_ring_buffer *buf = chan->backend.buf; | |
563 | ||
564 | lib_ring_buffer_stop_switch_timer(buf); | |
565 | lib_ring_buffer_stop_read_timer(buf); | |
566 | } | |
567 | channel_backend_unregister_notifiers(&chan->backend); | |
568 | } | |
569 | ||
570 | static void channel_free(struct channel *chan) | |
571 | { | |
572 | channel_iterator_free(chan); | |
573 | channel_backend_free(&chan->backend); | |
574 | kfree(chan); | |
575 | } | |
576 | ||
577 | /** | |
578 | * channel_create - Create channel. | |
579 | * @config: ring buffer instance configuration | |
580 | * @name: name of the channel | |
581 | * @priv: ring buffer client private data | |
582 | * @buf_addr: pointer the the beginning of the preallocated buffer contiguous | |
583 | * address mapping. It is used only by RING_BUFFER_STATIC | |
584 | * configuration. It can be set to NULL for other backends. | |
585 | * @subbuf_size: subbuffer size | |
586 | * @num_subbuf: number of subbuffers | |
587 | * @switch_timer_interval: Time interval (in us) to fill sub-buffers with | |
588 | * padding to let readers get those sub-buffers. | |
589 | * Used for live streaming. | |
590 | * @read_timer_interval: Time interval (in us) to wake up pending readers. | |
591 | * | |
592 | * Holds cpu hotplug. | |
593 | * Returns NULL on failure. | |
594 | */ | |
595 | struct channel *channel_create(const struct lib_ring_buffer_config *config, | |
596 | const char *name, void *priv, void *buf_addr, | |
597 | size_t subbuf_size, | |
598 | size_t num_subbuf, unsigned int switch_timer_interval, | |
599 | unsigned int read_timer_interval) | |
600 | { | |
601 | int ret, cpu; | |
602 | struct channel *chan; | |
603 | ||
604 | if (lib_ring_buffer_check_config(config, switch_timer_interval, | |
605 | read_timer_interval)) | |
606 | return NULL; | |
607 | ||
608 | chan = kzalloc(sizeof(struct channel), GFP_KERNEL); | |
609 | if (!chan) | |
610 | return NULL; | |
611 | ||
612 | ret = channel_backend_init(&chan->backend, name, config, priv, | |
613 | subbuf_size, num_subbuf); | |
614 | if (ret) | |
615 | goto error; | |
616 | ||
617 | ret = channel_iterator_init(chan); | |
618 | if (ret) | |
619 | goto error_free_backend; | |
620 | ||
621 | chan->commit_count_mask = (~0UL >> chan->backend.num_subbuf_order); | |
622 | chan->switch_timer_interval = usecs_to_jiffies(switch_timer_interval); | |
623 | chan->read_timer_interval = usecs_to_jiffies(read_timer_interval); | |
624 | kref_init(&chan->ref); | |
625 | init_waitqueue_head(&chan->read_wait); | |
626 | init_waitqueue_head(&chan->hp_wait); | |
627 | ||
628 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { | |
629 | #if defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER) | |
630 | /* Only benefit from NO_HZ idle with per-cpu buffers for now. */ | |
631 | chan->tick_nohz_notifier.notifier_call = | |
632 | ring_buffer_tick_nohz_callback; | |
633 | chan->tick_nohz_notifier.priority = ~0U; | |
634 | atomic_notifier_chain_register(&tick_nohz_notifier, | |
635 | &chan->tick_nohz_notifier); | |
636 | #endif /* defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER) */ | |
637 | ||
638 | /* | |
639 | * In case of non-hotplug cpu, if the ring-buffer is allocated | |
640 | * in early initcall, it will not be notified of secondary cpus. | |
641 | * In that off case, we need to allocate for all possible cpus. | |
642 | */ | |
643 | #ifdef CONFIG_HOTPLUG_CPU | |
644 | chan->cpu_hp_notifier.notifier_call = | |
645 | lib_ring_buffer_cpu_hp_callback; | |
646 | chan->cpu_hp_notifier.priority = 6; | |
647 | register_cpu_notifier(&chan->cpu_hp_notifier); | |
648 | ||
649 | get_online_cpus(); | |
650 | for_each_online_cpu(cpu) { | |
651 | struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, | |
652 | cpu); | |
653 | spin_lock(&per_cpu(ring_buffer_nohz_lock, cpu)); | |
654 | lib_ring_buffer_start_switch_timer(buf); | |
655 | lib_ring_buffer_start_read_timer(buf); | |
656 | spin_unlock(&per_cpu(ring_buffer_nohz_lock, cpu)); | |
657 | } | |
658 | chan->cpu_hp_enable = 1; | |
659 | put_online_cpus(); | |
660 | #else | |
661 | for_each_possible_cpu(cpu) { | |
662 | struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, | |
663 | cpu); | |
664 | spin_lock(&per_cpu(ring_buffer_nohz_lock, cpu)); | |
665 | lib_ring_buffer_start_switch_timer(buf); | |
666 | lib_ring_buffer_start_read_timer(buf); | |
667 | spin_unlock(&per_cpu(ring_buffer_nohz_lock, cpu)); | |
668 | } | |
669 | #endif | |
670 | } else { | |
671 | struct lib_ring_buffer *buf = chan->backend.buf; | |
672 | ||
673 | lib_ring_buffer_start_switch_timer(buf); | |
674 | lib_ring_buffer_start_read_timer(buf); | |
675 | } | |
676 | ||
677 | return chan; | |
678 | ||
679 | error_free_backend: | |
680 | channel_backend_free(&chan->backend); | |
681 | error: | |
682 | kfree(chan); | |
683 | return NULL; | |
684 | } | |
685 | EXPORT_SYMBOL_GPL(channel_create); | |
686 | ||
687 | static | |
688 | void channel_release(struct kref *kref) | |
689 | { | |
690 | struct channel *chan = container_of(kref, struct channel, ref); | |
691 | channel_free(chan); | |
692 | } | |
693 | ||
694 | /** | |
695 | * channel_destroy - Finalize, wait for q.s. and destroy channel. | |
696 | * @chan: channel to destroy | |
697 | * | |
698 | * Holds cpu hotplug. | |
699 | * Call "destroy" callback, finalize channels, wait for readers to release their | |
700 | * reference, then destroy ring buffer data. Note that when readers have | |
701 | * completed data consumption of finalized channels, get_subbuf() will return | |
702 | * -ENODATA. They should release their handle at that point. | |
703 | * Returns the private data pointer. | |
704 | */ | |
705 | void *channel_destroy(struct channel *chan) | |
706 | { | |
707 | int cpu; | |
708 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
709 | void *priv; | |
710 | ||
711 | channel_unregister_notifiers(chan); | |
712 | ||
713 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { | |
714 | /* | |
715 | * No need to hold cpu hotplug, because all notifiers have been | |
716 | * unregistered. | |
717 | */ | |
718 | for_each_channel_cpu(cpu, chan) { | |
719 | struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, | |
720 | cpu); | |
721 | ||
722 | if (config->cb.buffer_finalize) | |
723 | config->cb.buffer_finalize(buf, | |
724 | chan->backend.priv, | |
725 | cpu); | |
726 | if (buf->backend.allocated) | |
727 | lib_ring_buffer_switch_slow(buf, SWITCH_FLUSH); | |
728 | /* | |
729 | * Perform flush before writing to finalized. | |
730 | */ | |
731 | smp_wmb(); | |
732 | ACCESS_ONCE(buf->finalized) = 1; | |
733 | wake_up_interruptible(&buf->read_wait); | |
734 | } | |
735 | } else { | |
736 | struct lib_ring_buffer *buf = chan->backend.buf; | |
737 | ||
738 | if (config->cb.buffer_finalize) | |
739 | config->cb.buffer_finalize(buf, chan->backend.priv, -1); | |
740 | if (buf->backend.allocated) | |
741 | lib_ring_buffer_switch_slow(buf, SWITCH_FLUSH); | |
742 | /* | |
743 | * Perform flush before writing to finalized. | |
744 | */ | |
745 | smp_wmb(); | |
746 | ACCESS_ONCE(buf->finalized) = 1; | |
747 | wake_up_interruptible(&buf->read_wait); | |
748 | } | |
749 | ACCESS_ONCE(chan->finalized) = 1; | |
750 | wake_up_interruptible(&chan->hp_wait); | |
751 | wake_up_interruptible(&chan->read_wait); | |
752 | kref_put(&chan->ref, channel_release); | |
753 | priv = chan->backend.priv; | |
754 | return priv; | |
755 | } | |
756 | EXPORT_SYMBOL_GPL(channel_destroy); | |
757 | ||
758 | struct lib_ring_buffer *channel_get_ring_buffer( | |
759 | const struct lib_ring_buffer_config *config, | |
760 | struct channel *chan, int cpu) | |
761 | { | |
762 | if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) | |
763 | return chan->backend.buf; | |
764 | else | |
765 | return per_cpu_ptr(chan->backend.buf, cpu); | |
766 | } | |
767 | EXPORT_SYMBOL_GPL(channel_get_ring_buffer); | |
768 | ||
769 | int lib_ring_buffer_open_read(struct lib_ring_buffer *buf) | |
770 | { | |
771 | struct channel *chan = buf->backend.chan; | |
772 | ||
773 | if (!atomic_long_add_unless(&buf->active_readers, 1, 1)) | |
774 | return -EBUSY; | |
775 | kref_get(&chan->ref); | |
776 | smp_mb__after_atomic_inc(); | |
777 | return 0; | |
778 | } | |
779 | EXPORT_SYMBOL_GPL(lib_ring_buffer_open_read); | |
780 | ||
781 | void lib_ring_buffer_release_read(struct lib_ring_buffer *buf) | |
782 | { | |
783 | struct channel *chan = buf->backend.chan; | |
784 | ||
785 | CHAN_WARN_ON(chan, atomic_long_read(&buf->active_readers) != 1); | |
786 | smp_mb__before_atomic_dec(); | |
787 | atomic_long_dec(&buf->active_readers); | |
788 | kref_put(&chan->ref, channel_release); | |
789 | } | |
790 | EXPORT_SYMBOL_GPL(lib_ring_buffer_release_read); | |
791 | ||
792 | /* | |
793 | * Promote compiler barrier to a smp_mb(). | |
794 | * For the specific ring buffer case, this IPI call should be removed if the | |
795 | * architecture does not reorder writes. This should eventually be provided by | |
796 | * a separate architecture-specific infrastructure. | |
797 | */ | |
798 | static void remote_mb(void *info) | |
799 | { | |
800 | smp_mb(); | |
801 | } | |
802 | ||
803 | /** | |
804 | * lib_ring_buffer_snapshot - save subbuffer position snapshot (for read) | |
805 | * @buf: ring buffer | |
806 | * @consumed: consumed count indicating the position where to read | |
807 | * @produced: produced count, indicates position when to stop reading | |
808 | * | |
809 | * Returns -ENODATA if buffer is finalized, -EAGAIN if there is currently no | |
810 | * data to read at consumed position, or 0 if the get operation succeeds. | |
811 | * Busy-loop trying to get data if the tick_nohz sequence lock is held. | |
812 | */ | |
813 | ||
814 | int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf, | |
815 | unsigned long *consumed, unsigned long *produced) | |
816 | { | |
817 | struct channel *chan = buf->backend.chan; | |
818 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
819 | unsigned long consumed_cur, write_offset; | |
820 | int finalized; | |
821 | ||
822 | retry: | |
823 | finalized = ACCESS_ONCE(buf->finalized); | |
824 | /* | |
825 | * Read finalized before counters. | |
826 | */ | |
827 | smp_rmb(); | |
828 | consumed_cur = atomic_long_read(&buf->consumed); | |
829 | /* | |
830 | * No need to issue a memory barrier between consumed count read and | |
831 | * write offset read, because consumed count can only change | |
832 | * concurrently in overwrite mode, and we keep a sequence counter | |
833 | * identifier derived from the write offset to check we are getting | |
834 | * the same sub-buffer we are expecting (the sub-buffers are atomically | |
835 | * "tagged" upon writes, tags are checked upon read). | |
836 | */ | |
837 | write_offset = v_read(config, &buf->offset); | |
838 | ||
839 | /* | |
840 | * Check that we are not about to read the same subbuffer in | |
841 | * which the writer head is. | |
842 | */ | |
843 | if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_cur, chan) | |
844 | == 0) | |
845 | goto nodata; | |
846 | ||
847 | *consumed = consumed_cur; | |
848 | *produced = subbuf_trunc(write_offset, chan); | |
849 | ||
850 | return 0; | |
851 | ||
852 | nodata: | |
853 | /* | |
854 | * The memory barriers __wait_event()/wake_up_interruptible() take care | |
855 | * of "raw_spin_is_locked" memory ordering. | |
856 | */ | |
857 | if (finalized) | |
858 | return -ENODATA; | |
859 | else if (raw_spin_is_locked(&buf->raw_tick_nohz_spinlock)) | |
860 | goto retry; | |
861 | else | |
862 | return -EAGAIN; | |
863 | } | |
864 | EXPORT_SYMBOL_GPL(lib_ring_buffer_snapshot); | |
865 | ||
866 | /** | |
867 | * lib_ring_buffer_put_snapshot - move consumed counter forward | |
868 | * @buf: ring buffer | |
869 | * @consumed_new: new consumed count value | |
870 | */ | |
871 | void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf, | |
872 | unsigned long consumed_new) | |
873 | { | |
874 | struct lib_ring_buffer_backend *bufb = &buf->backend; | |
875 | struct channel *chan = bufb->chan; | |
876 | unsigned long consumed; | |
877 | ||
878 | CHAN_WARN_ON(chan, atomic_long_read(&buf->active_readers) != 1); | |
879 | ||
880 | /* | |
881 | * Only push the consumed value forward. | |
882 | * If the consumed cmpxchg fails, this is because we have been pushed by | |
883 | * the writer in flight recorder mode. | |
884 | */ | |
885 | consumed = atomic_long_read(&buf->consumed); | |
886 | while ((long) consumed - (long) consumed_new < 0) | |
887 | consumed = atomic_long_cmpxchg(&buf->consumed, consumed, | |
888 | consumed_new); | |
889 | } | |
890 | EXPORT_SYMBOL_GPL(lib_ring_buffer_move_consumer); | |
891 | ||
892 | /** | |
893 | * lib_ring_buffer_get_subbuf - get exclusive access to subbuffer for reading | |
894 | * @buf: ring buffer | |
895 | * @consumed: consumed count indicating the position where to read | |
896 | * | |
897 | * Returns -ENODATA if buffer is finalized, -EAGAIN if there is currently no | |
898 | * data to read at consumed position, or 0 if the get operation succeeds. | |
899 | * Busy-loop trying to get data if the tick_nohz sequence lock is held. | |
900 | */ | |
901 | int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf, | |
902 | unsigned long consumed) | |
903 | { | |
904 | struct channel *chan = buf->backend.chan; | |
905 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
906 | unsigned long consumed_cur, consumed_idx, commit_count, write_offset; | |
907 | int ret; | |
908 | int finalized; | |
909 | ||
910 | retry: | |
911 | finalized = ACCESS_ONCE(buf->finalized); | |
912 | /* | |
913 | * Read finalized before counters. | |
914 | */ | |
915 | smp_rmb(); | |
916 | consumed_cur = atomic_long_read(&buf->consumed); | |
917 | consumed_idx = subbuf_index(consumed, chan); | |
918 | commit_count = v_read(config, &buf->commit_cold[consumed_idx].cc_sb); | |
919 | /* | |
920 | * Make sure we read the commit count before reading the buffer | |
921 | * data and the write offset. Correct consumed offset ordering | |
922 | * wrt commit count is insured by the use of cmpxchg to update | |
923 | * the consumed offset. | |
924 | * smp_call_function_single can fail if the remote CPU is offline, | |
925 | * this is OK because then there is no wmb to execute there. | |
926 | * If our thread is executing on the same CPU as the on the buffers | |
927 | * belongs to, we don't have to synchronize it at all. If we are | |
928 | * migrated, the scheduler will take care of the memory barriers. | |
929 | * Normally, smp_call_function_single() should ensure program order when | |
930 | * executing the remote function, which implies that it surrounds the | |
931 | * function execution with : | |
932 | * smp_mb() | |
933 | * send IPI | |
934 | * csd_lock_wait | |
935 | * recv IPI | |
936 | * smp_mb() | |
937 | * exec. function | |
938 | * smp_mb() | |
939 | * csd unlock | |
940 | * smp_mb() | |
941 | * | |
942 | * However, smp_call_function_single() does not seem to clearly execute | |
943 | * such barriers. It depends on spinlock semantic to provide the barrier | |
944 | * before executing the IPI and, when busy-looping, csd_lock_wait only | |
945 | * executes smp_mb() when it has to wait for the other CPU. | |
946 | * | |
947 | * I don't trust this code. Therefore, let's add the smp_mb() sequence | |
948 | * required ourself, even if duplicated. It has no performance impact | |
949 | * anyway. | |
950 | * | |
951 | * smp_mb() is needed because smp_rmb() and smp_wmb() only order read vs | |
952 | * read and write vs write. They do not ensure core synchronization. We | |
953 | * really have to ensure total order between the 3 barriers running on | |
954 | * the 2 CPUs. | |
955 | */ | |
956 | if (config->ipi == RING_BUFFER_IPI_BARRIER) { | |
957 | if (config->sync == RING_BUFFER_SYNC_PER_CPU | |
958 | && config->alloc == RING_BUFFER_ALLOC_PER_CPU) { | |
959 | if (raw_smp_processor_id() != buf->backend.cpu) { | |
960 | /* Total order with IPI handler smp_mb() */ | |
961 | smp_mb(); | |
962 | smp_call_function_single(buf->backend.cpu, | |
963 | remote_mb, NULL, 1); | |
964 | /* Total order with IPI handler smp_mb() */ | |
965 | smp_mb(); | |
966 | } | |
967 | } else { | |
968 | /* Total order with IPI handler smp_mb() */ | |
969 | smp_mb(); | |
970 | smp_call_function(remote_mb, NULL, 1); | |
971 | /* Total order with IPI handler smp_mb() */ | |
972 | smp_mb(); | |
973 | } | |
974 | } else { | |
975 | /* | |
976 | * Local rmb to match the remote wmb to read the commit count | |
977 | * before the buffer data and the write offset. | |
978 | */ | |
979 | smp_rmb(); | |
980 | } | |
981 | ||
982 | write_offset = v_read(config, &buf->offset); | |
983 | ||
984 | /* | |
985 | * Check that the buffer we are getting is after or at consumed_cur | |
986 | * position. | |
987 | */ | |
988 | if ((long) subbuf_trunc(consumed, chan) | |
989 | - (long) subbuf_trunc(consumed_cur, chan) < 0) | |
990 | goto nodata; | |
991 | ||
992 | /* | |
993 | * Check that the subbuffer we are trying to consume has been | |
994 | * already fully committed. | |
995 | */ | |
996 | if (((commit_count - chan->backend.subbuf_size) | |
997 | & chan->commit_count_mask) | |
998 | - (buf_trunc(consumed_cur, chan) | |
999 | >> chan->backend.num_subbuf_order) | |
1000 | != 0) | |
1001 | goto nodata; | |
1002 | ||
1003 | /* | |
1004 | * Check that we are not about to read the same subbuffer in | |
1005 | * which the writer head is. | |
1006 | */ | |
1007 | if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_cur, chan) | |
1008 | == 0) | |
1009 | goto nodata; | |
1010 | ||
1011 | /* | |
1012 | * Failure to get the subbuffer causes a busy-loop retry without going | |
1013 | * to a wait queue. These are caused by short-lived race windows where | |
1014 | * the writer is getting access to a subbuffer we were trying to get | |
1015 | * access to. Also checks that the "consumed" buffer count we are | |
1016 | * looking for matches the one contained in the subbuffer id. | |
1017 | */ | |
1018 | ret = update_read_sb_index(config, &buf->backend, &chan->backend, | |
1019 | consumed_idx, buf_trunc_val(consumed, chan)); | |
1020 | if (ret) | |
1021 | goto retry; | |
1022 | subbuffer_id_clear_noref(config, &buf->backend.buf_rsb.id); | |
1023 | ||
1024 | buf->get_subbuf_consumed = consumed; | |
1025 | buf->get_subbuf = 1; | |
1026 | ||
1027 | return 0; | |
1028 | ||
1029 | nodata: | |
1030 | /* | |
1031 | * The memory barriers __wait_event()/wake_up_interruptible() take care | |
1032 | * of "raw_spin_is_locked" memory ordering. | |
1033 | */ | |
1034 | if (finalized) | |
1035 | return -ENODATA; | |
1036 | else if (raw_spin_is_locked(&buf->raw_tick_nohz_spinlock)) | |
1037 | goto retry; | |
1038 | else | |
1039 | return -EAGAIN; | |
1040 | } | |
1041 | EXPORT_SYMBOL_GPL(lib_ring_buffer_get_subbuf); | |
1042 | ||
1043 | /** | |
1044 | * lib_ring_buffer_put_subbuf - release exclusive subbuffer access | |
1045 | * @buf: ring buffer | |
1046 | */ | |
1047 | void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf) | |
1048 | { | |
1049 | struct lib_ring_buffer_backend *bufb = &buf->backend; | |
1050 | struct channel *chan = bufb->chan; | |
1051 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1052 | unsigned long read_sb_bindex, consumed_idx, consumed; | |
1053 | ||
1054 | CHAN_WARN_ON(chan, atomic_long_read(&buf->active_readers) != 1); | |
1055 | ||
1056 | if (!buf->get_subbuf) { | |
1057 | /* | |
1058 | * Reader puts a subbuffer it did not get. | |
1059 | */ | |
1060 | CHAN_WARN_ON(chan, 1); | |
1061 | return; | |
1062 | } | |
1063 | consumed = buf->get_subbuf_consumed; | |
1064 | buf->get_subbuf = 0; | |
1065 | ||
1066 | /* | |
1067 | * Clear the records_unread counter. (overruns counter) | |
1068 | * Can still be non-zero if a file reader simply grabbed the data | |
1069 | * without using iterators. | |
1070 | * Can be below zero if an iterator is used on a snapshot more than | |
1071 | * once. | |
1072 | */ | |
1073 | read_sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
1074 | v_add(config, v_read(config, | |
1075 | &bufb->array[read_sb_bindex]->records_unread), | |
1076 | &bufb->records_read); | |
1077 | v_set(config, &bufb->array[read_sb_bindex]->records_unread, 0); | |
1078 | CHAN_WARN_ON(chan, config->mode == RING_BUFFER_OVERWRITE | |
1079 | && subbuffer_id_is_noref(config, bufb->buf_rsb.id)); | |
1080 | subbuffer_id_set_noref(config, &bufb->buf_rsb.id); | |
1081 | ||
1082 | /* | |
1083 | * Exchange the reader subbuffer with the one we put in its place in the | |
1084 | * writer subbuffer table. Expect the original consumed count. If | |
1085 | * update_read_sb_index fails, this is because the writer updated the | |
1086 | * subbuffer concurrently. We should therefore keep the subbuffer we | |
1087 | * currently have: it has become invalid to try reading this sub-buffer | |
1088 | * consumed count value anyway. | |
1089 | */ | |
1090 | consumed_idx = subbuf_index(consumed, chan); | |
1091 | update_read_sb_index(config, &buf->backend, &chan->backend, | |
1092 | consumed_idx, buf_trunc_val(consumed, chan)); | |
1093 | /* | |
1094 | * update_read_sb_index return value ignored. Don't exchange sub-buffer | |
1095 | * if the writer concurrently updated it. | |
1096 | */ | |
1097 | } | |
1098 | EXPORT_SYMBOL_GPL(lib_ring_buffer_put_subbuf); | |
1099 | ||
1100 | /* | |
1101 | * cons_offset is an iterator on all subbuffer offsets between the reader | |
1102 | * position and the writer position. (inclusive) | |
1103 | */ | |
1104 | static | |
1105 | void lib_ring_buffer_print_subbuffer_errors(struct lib_ring_buffer *buf, | |
1106 | struct channel *chan, | |
1107 | unsigned long cons_offset, | |
1108 | int cpu) | |
1109 | { | |
1110 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1111 | unsigned long cons_idx, commit_count, commit_count_sb; | |
1112 | ||
1113 | cons_idx = subbuf_index(cons_offset, chan); | |
1114 | commit_count = v_read(config, &buf->commit_hot[cons_idx].cc); | |
1115 | commit_count_sb = v_read(config, &buf->commit_cold[cons_idx].cc_sb); | |
1116 | ||
1117 | if (subbuf_offset(commit_count, chan) != 0) | |
1118 | printk(KERN_WARNING | |
1119 | "ring buffer %s, cpu %d: " | |
1120 | "commit count in subbuffer %lu,\n" | |
1121 | "expecting multiples of %lu bytes\n" | |
1122 | " [ %lu bytes committed, %lu bytes reader-visible ]\n", | |
1123 | chan->backend.name, cpu, cons_idx, | |
1124 | chan->backend.subbuf_size, | |
1125 | commit_count, commit_count_sb); | |
1126 | ||
1127 | printk(KERN_DEBUG "ring buffer: %s, cpu %d: %lu bytes committed\n", | |
1128 | chan->backend.name, cpu, commit_count); | |
1129 | } | |
1130 | ||
1131 | static | |
1132 | void lib_ring_buffer_print_buffer_errors(struct lib_ring_buffer *buf, | |
1133 | struct channel *chan, | |
1134 | void *priv, int cpu) | |
1135 | { | |
1136 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1137 | unsigned long write_offset, cons_offset; | |
1138 | ||
1139 | /* | |
1140 | * Can be called in the error path of allocation when | |
1141 | * trans_channel_data is not yet set. | |
1142 | */ | |
1143 | if (!chan) | |
1144 | return; | |
1145 | /* | |
1146 | * No need to order commit_count, write_offset and cons_offset reads | |
1147 | * because we execute at teardown when no more writer nor reader | |
1148 | * references are left. | |
1149 | */ | |
1150 | write_offset = v_read(config, &buf->offset); | |
1151 | cons_offset = atomic_long_read(&buf->consumed); | |
1152 | if (write_offset != cons_offset) | |
1153 | printk(KERN_WARNING | |
1154 | "ring buffer %s, cpu %d: " | |
1155 | "non-consumed data\n" | |
1156 | " [ %lu bytes written, %lu bytes read ]\n", | |
1157 | chan->backend.name, cpu, write_offset, cons_offset); | |
1158 | ||
1159 | for (cons_offset = atomic_long_read(&buf->consumed); | |
1160 | (long) (subbuf_trunc((unsigned long) v_read(config, &buf->offset), | |
1161 | chan) | |
1162 | - cons_offset) > 0; | |
1163 | cons_offset = subbuf_align(cons_offset, chan)) | |
1164 | lib_ring_buffer_print_subbuffer_errors(buf, chan, cons_offset, | |
1165 | cpu); | |
1166 | } | |
1167 | ||
1168 | static | |
1169 | void lib_ring_buffer_print_errors(struct channel *chan, | |
1170 | struct lib_ring_buffer *buf, int cpu) | |
1171 | { | |
1172 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1173 | void *priv = chan->backend.priv; | |
1174 | ||
1175 | printk(KERN_DEBUG "ring buffer %s, cpu %d: %lu records written, " | |
1176 | "%lu records overrun\n", | |
1177 | chan->backend.name, cpu, | |
1178 | v_read(config, &buf->records_count), | |
1179 | v_read(config, &buf->records_overrun)); | |
1180 | ||
1181 | if (v_read(config, &buf->records_lost_full) | |
1182 | || v_read(config, &buf->records_lost_wrap) | |
1183 | || v_read(config, &buf->records_lost_big)) | |
1184 | printk(KERN_WARNING | |
1185 | "ring buffer %s, cpu %d: records were lost. Caused by:\n" | |
1186 | " [ %lu buffer full, %lu nest buffer wrap-around, " | |
1187 | "%lu event too big ]\n", | |
1188 | chan->backend.name, cpu, | |
1189 | v_read(config, &buf->records_lost_full), | |
1190 | v_read(config, &buf->records_lost_wrap), | |
1191 | v_read(config, &buf->records_lost_big)); | |
1192 | ||
1193 | lib_ring_buffer_print_buffer_errors(buf, chan, priv, cpu); | |
1194 | } | |
1195 | ||
1196 | /* | |
1197 | * lib_ring_buffer_switch_old_start: Populate old subbuffer header. | |
1198 | * | |
1199 | * Only executed when the buffer is finalized, in SWITCH_FLUSH. | |
1200 | */ | |
1201 | static | |
1202 | void lib_ring_buffer_switch_old_start(struct lib_ring_buffer *buf, | |
1203 | struct channel *chan, | |
1204 | struct switch_offsets *offsets, | |
1205 | u64 tsc) | |
1206 | { | |
1207 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1208 | unsigned long oldidx = subbuf_index(offsets->old, chan); | |
1209 | unsigned long commit_count; | |
1210 | ||
1211 | config->cb.buffer_begin(buf, tsc, oldidx); | |
1212 | ||
1213 | /* | |
1214 | * Order all writes to buffer before the commit count update that will | |
1215 | * determine that the subbuffer is full. | |
1216 | */ | |
1217 | if (config->ipi == RING_BUFFER_IPI_BARRIER) { | |
1218 | /* | |
1219 | * Must write slot data before incrementing commit count. This | |
1220 | * compiler barrier is upgraded into a smp_mb() by the IPI sent | |
1221 | * by get_subbuf(). | |
1222 | */ | |
1223 | barrier(); | |
1224 | } else | |
1225 | smp_wmb(); | |
1226 | v_add(config, config->cb.subbuffer_header_size(), | |
1227 | &buf->commit_hot[oldidx].cc); | |
1228 | commit_count = v_read(config, &buf->commit_hot[oldidx].cc); | |
1229 | /* Check if the written buffer has to be delivered */ | |
1230 | lib_ring_buffer_check_deliver(config, buf, chan, offsets->old, | |
1231 | commit_count, oldidx); | |
1232 | lib_ring_buffer_write_commit_counter(config, buf, chan, oldidx, | |
1233 | offsets->old, commit_count, | |
1234 | config->cb.subbuffer_header_size()); | |
1235 | } | |
1236 | ||
1237 | /* | |
1238 | * lib_ring_buffer_switch_old_end: switch old subbuffer | |
1239 | * | |
1240 | * Note : offset_old should never be 0 here. It is ok, because we never perform | |
1241 | * buffer switch on an empty subbuffer in SWITCH_ACTIVE mode. The caller | |
1242 | * increments the offset_old value when doing a SWITCH_FLUSH on an empty | |
1243 | * subbuffer. | |
1244 | */ | |
1245 | static | |
1246 | void lib_ring_buffer_switch_old_end(struct lib_ring_buffer *buf, | |
1247 | struct channel *chan, | |
1248 | struct switch_offsets *offsets, | |
1249 | u64 tsc) | |
1250 | { | |
1251 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1252 | unsigned long oldidx = subbuf_index(offsets->old - 1, chan); | |
1253 | unsigned long commit_count, padding_size, data_size; | |
1254 | ||
1255 | data_size = subbuf_offset(offsets->old - 1, chan) + 1; | |
1256 | padding_size = chan->backend.subbuf_size - data_size; | |
1257 | subbuffer_set_data_size(config, &buf->backend, oldidx, data_size); | |
1258 | ||
1259 | /* | |
1260 | * Order all writes to buffer before the commit count update that will | |
1261 | * determine that the subbuffer is full. | |
1262 | */ | |
1263 | if (config->ipi == RING_BUFFER_IPI_BARRIER) { | |
1264 | /* | |
1265 | * Must write slot data before incrementing commit count. This | |
1266 | * compiler barrier is upgraded into a smp_mb() by the IPI sent | |
1267 | * by get_subbuf(). | |
1268 | */ | |
1269 | barrier(); | |
1270 | } else | |
1271 | smp_wmb(); | |
1272 | v_add(config, padding_size, &buf->commit_hot[oldidx].cc); | |
1273 | commit_count = v_read(config, &buf->commit_hot[oldidx].cc); | |
1274 | lib_ring_buffer_check_deliver(config, buf, chan, offsets->old - 1, | |
1275 | commit_count, oldidx); | |
1276 | lib_ring_buffer_write_commit_counter(config, buf, chan, oldidx, | |
1277 | offsets->old, commit_count, | |
1278 | padding_size); | |
1279 | } | |
1280 | ||
1281 | /* | |
1282 | * lib_ring_buffer_switch_new_start: Populate new subbuffer. | |
1283 | * | |
1284 | * This code can be executed unordered : writers may already have written to the | |
1285 | * sub-buffer before this code gets executed, caution. The commit makes sure | |
1286 | * that this code is executed before the deliver of this sub-buffer. | |
1287 | */ | |
1288 | static | |
1289 | void lib_ring_buffer_switch_new_start(struct lib_ring_buffer *buf, | |
1290 | struct channel *chan, | |
1291 | struct switch_offsets *offsets, | |
1292 | u64 tsc) | |
1293 | { | |
1294 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1295 | unsigned long beginidx = subbuf_index(offsets->begin, chan); | |
1296 | unsigned long commit_count; | |
1297 | ||
1298 | config->cb.buffer_begin(buf, tsc, beginidx); | |
1299 | ||
1300 | /* | |
1301 | * Order all writes to buffer before the commit count update that will | |
1302 | * determine that the subbuffer is full. | |
1303 | */ | |
1304 | if (config->ipi == RING_BUFFER_IPI_BARRIER) { | |
1305 | /* | |
1306 | * Must write slot data before incrementing commit count. This | |
1307 | * compiler barrier is upgraded into a smp_mb() by the IPI sent | |
1308 | * by get_subbuf(). | |
1309 | */ | |
1310 | barrier(); | |
1311 | } else | |
1312 | smp_wmb(); | |
1313 | v_add(config, config->cb.subbuffer_header_size(), | |
1314 | &buf->commit_hot[beginidx].cc); | |
1315 | commit_count = v_read(config, &buf->commit_hot[beginidx].cc); | |
1316 | /* Check if the written buffer has to be delivered */ | |
1317 | lib_ring_buffer_check_deliver(config, buf, chan, offsets->begin, | |
1318 | commit_count, beginidx); | |
1319 | lib_ring_buffer_write_commit_counter(config, buf, chan, beginidx, | |
1320 | offsets->begin, commit_count, | |
1321 | config->cb.subbuffer_header_size()); | |
1322 | } | |
1323 | ||
1324 | /* | |
1325 | * lib_ring_buffer_switch_new_end: finish switching current subbuffer | |
1326 | * | |
1327 | * The only remaining threads could be the ones with pending commits. They will | |
1328 | * have to do the deliver themselves. | |
1329 | */ | |
1330 | static | |
1331 | void lib_ring_buffer_switch_new_end(struct lib_ring_buffer *buf, | |
1332 | struct channel *chan, | |
1333 | struct switch_offsets *offsets, | |
1334 | u64 tsc) | |
1335 | { | |
1336 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1337 | unsigned long endidx = subbuf_index(offsets->end - 1, chan); | |
1338 | unsigned long commit_count, padding_size, data_size; | |
1339 | ||
1340 | data_size = subbuf_offset(offsets->end - 1, chan) + 1; | |
1341 | padding_size = chan->backend.subbuf_size - data_size; | |
1342 | subbuffer_set_data_size(config, &buf->backend, endidx, data_size); | |
1343 | ||
1344 | /* | |
1345 | * Order all writes to buffer before the commit count update that will | |
1346 | * determine that the subbuffer is full. | |
1347 | */ | |
1348 | if (config->ipi == RING_BUFFER_IPI_BARRIER) { | |
1349 | /* | |
1350 | * Must write slot data before incrementing commit count. This | |
1351 | * compiler barrier is upgraded into a smp_mb() by the IPI sent | |
1352 | * by get_subbuf(). | |
1353 | */ | |
1354 | barrier(); | |
1355 | } else | |
1356 | smp_wmb(); | |
1357 | v_add(config, padding_size, &buf->commit_hot[endidx].cc); | |
1358 | commit_count = v_read(config, &buf->commit_hot[endidx].cc); | |
1359 | lib_ring_buffer_check_deliver(config, buf, chan, offsets->end - 1, | |
1360 | commit_count, endidx); | |
1361 | lib_ring_buffer_write_commit_counter(config, buf, chan, endidx, | |
1362 | offsets->end, commit_count, | |
1363 | padding_size); | |
1364 | } | |
1365 | ||
1366 | /* | |
1367 | * Returns : | |
1368 | * 0 if ok | |
1369 | * !0 if execution must be aborted. | |
1370 | */ | |
1371 | static | |
1372 | int lib_ring_buffer_try_switch_slow(enum switch_mode mode, | |
1373 | struct lib_ring_buffer *buf, | |
1374 | struct channel *chan, | |
1375 | struct switch_offsets *offsets, | |
1376 | u64 *tsc) | |
1377 | { | |
1378 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1379 | unsigned long off; | |
1380 | ||
1381 | offsets->begin = v_read(config, &buf->offset); | |
1382 | offsets->old = offsets->begin; | |
1383 | offsets->switch_old_start = 0; | |
1384 | off = subbuf_offset(offsets->begin, chan); | |
1385 | ||
1386 | *tsc = config->cb.ring_buffer_clock_read(chan); | |
1387 | ||
1388 | /* | |
1389 | * Ensure we flush the header of an empty subbuffer when doing the | |
1390 | * finalize (SWITCH_FLUSH). This ensures that we end up knowing the | |
1391 | * total data gathering duration even if there were no records saved | |
1392 | * after the last buffer switch. | |
1393 | * In SWITCH_ACTIVE mode, switch the buffer when it contains events. | |
1394 | * SWITCH_ACTIVE only flushes the current subbuffer, dealing with end of | |
1395 | * subbuffer header as appropriate. | |
1396 | * The next record that reserves space will be responsible for | |
1397 | * populating the following subbuffer header. We choose not to populate | |
1398 | * the next subbuffer header here because we want to be able to use | |
1399 | * SWITCH_ACTIVE for periodical buffer flush and CPU tick_nohz stop | |
1400 | * buffer flush, which must guarantee that all the buffer content | |
1401 | * (records and header timestamps) are visible to the reader. This is | |
1402 | * required for quiescence guarantees for the fusion merge. | |
1403 | */ | |
1404 | if (mode == SWITCH_FLUSH || off > 0) { | |
1405 | if (unlikely(off == 0)) { | |
1406 | /* | |
1407 | * The client does not save any header information. | |
1408 | * Don't switch empty subbuffer on finalize, because it | |
1409 | * is invalid to deliver a completely empty subbuffer. | |
1410 | */ | |
1411 | if (!config->cb.subbuffer_header_size()) | |
1412 | return -1; | |
1413 | /* | |
1414 | * Need to write the subbuffer start header on finalize. | |
1415 | */ | |
1416 | offsets->switch_old_start = 1; | |
1417 | } | |
1418 | offsets->begin = subbuf_align(offsets->begin, chan); | |
1419 | } else | |
1420 | return -1; /* we do not have to switch : buffer is empty */ | |
1421 | /* Note: old points to the next subbuf at offset 0 */ | |
1422 | offsets->end = offsets->begin; | |
1423 | return 0; | |
1424 | } | |
1425 | ||
1426 | /* | |
1427 | * Force a sub-buffer switch. This operation is completely reentrant : can be | |
1428 | * called while tracing is active with absolutely no lock held. | |
1429 | * | |
1430 | * Note, however, that as a v_cmpxchg is used for some atomic | |
1431 | * operations, this function must be called from the CPU which owns the buffer | |
1432 | * for a ACTIVE flush. | |
1433 | */ | |
1434 | void lib_ring_buffer_switch_slow(struct lib_ring_buffer *buf, enum switch_mode mode) | |
1435 | { | |
1436 | struct channel *chan = buf->backend.chan; | |
1437 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1438 | struct switch_offsets offsets; | |
1439 | unsigned long oldidx; | |
1440 | u64 tsc; | |
1441 | ||
1442 | offsets.size = 0; | |
1443 | ||
1444 | /* | |
1445 | * Perform retryable operations. | |
1446 | */ | |
1447 | do { | |
1448 | if (lib_ring_buffer_try_switch_slow(mode, buf, chan, &offsets, | |
1449 | &tsc)) | |
1450 | return; /* Switch not needed */ | |
1451 | } while (v_cmpxchg(config, &buf->offset, offsets.old, offsets.end) | |
1452 | != offsets.old); | |
1453 | ||
1454 | /* | |
1455 | * Atomically update last_tsc. This update races against concurrent | |
1456 | * atomic updates, but the race will always cause supplementary full TSC | |
1457 | * records, never the opposite (missing a full TSC record when it would | |
1458 | * be needed). | |
1459 | */ | |
1460 | save_last_tsc(config, buf, tsc); | |
1461 | ||
1462 | /* | |
1463 | * Push the reader if necessary | |
1464 | */ | |
1465 | lib_ring_buffer_reserve_push_reader(buf, chan, offsets.old); | |
1466 | ||
1467 | oldidx = subbuf_index(offsets.old, chan); | |
1468 | lib_ring_buffer_clear_noref(config, &buf->backend, oldidx); | |
1469 | ||
1470 | /* | |
1471 | * May need to populate header start on SWITCH_FLUSH. | |
1472 | */ | |
1473 | if (offsets.switch_old_start) { | |
1474 | lib_ring_buffer_switch_old_start(buf, chan, &offsets, tsc); | |
1475 | offsets.old += config->cb.subbuffer_header_size(); | |
1476 | } | |
1477 | ||
1478 | /* | |
1479 | * Switch old subbuffer. | |
1480 | */ | |
1481 | lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc); | |
1482 | } | |
1483 | EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_slow); | |
1484 | ||
1485 | /* | |
1486 | * Returns : | |
1487 | * 0 if ok | |
1488 | * -ENOSPC if event size is too large for packet. | |
1489 | * -ENOBUFS if there is currently not enough space in buffer for the event. | |
1490 | * -EIO if data cannot be written into the buffer for any other reason. | |
1491 | */ | |
1492 | static | |
1493 | int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf, | |
1494 | struct channel *chan, | |
1495 | struct switch_offsets *offsets, | |
1496 | struct lib_ring_buffer_ctx *ctx) | |
1497 | { | |
1498 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1499 | unsigned long reserve_commit_diff; | |
1500 | ||
1501 | offsets->begin = v_read(config, &buf->offset); | |
1502 | offsets->old = offsets->begin; | |
1503 | offsets->switch_new_start = 0; | |
1504 | offsets->switch_new_end = 0; | |
1505 | offsets->switch_old_end = 0; | |
1506 | offsets->pre_header_padding = 0; | |
1507 | ||
1508 | ctx->tsc = config->cb.ring_buffer_clock_read(chan); | |
1509 | if ((int64_t) ctx->tsc == -EIO) | |
1510 | return -EIO; | |
1511 | ||
1512 | if (last_tsc_overflow(config, buf, ctx->tsc)) | |
1513 | ctx->rflags |= RING_BUFFER_RFLAG_FULL_TSC; | |
1514 | ||
1515 | if (unlikely(subbuf_offset(offsets->begin, ctx->chan) == 0)) { | |
1516 | offsets->switch_new_start = 1; /* For offsets->begin */ | |
1517 | } else { | |
1518 | offsets->size = config->cb.record_header_size(config, chan, | |
1519 | offsets->begin, | |
1520 | &offsets->pre_header_padding, | |
1521 | ctx); | |
1522 | offsets->size += | |
1523 | lib_ring_buffer_align(offsets->begin + offsets->size, | |
1524 | ctx->largest_align) | |
1525 | + ctx->data_size; | |
1526 | if (unlikely(subbuf_offset(offsets->begin, chan) + | |
1527 | offsets->size > chan->backend.subbuf_size)) { | |
1528 | offsets->switch_old_end = 1; /* For offsets->old */ | |
1529 | offsets->switch_new_start = 1; /* For offsets->begin */ | |
1530 | } | |
1531 | } | |
1532 | if (unlikely(offsets->switch_new_start)) { | |
1533 | unsigned long sb_index; | |
1534 | ||
1535 | /* | |
1536 | * We are typically not filling the previous buffer completely. | |
1537 | */ | |
1538 | if (likely(offsets->switch_old_end)) | |
1539 | offsets->begin = subbuf_align(offsets->begin, chan); | |
1540 | offsets->begin = offsets->begin | |
1541 | + config->cb.subbuffer_header_size(); | |
1542 | /* Test new buffer integrity */ | |
1543 | sb_index = subbuf_index(offsets->begin, chan); | |
1544 | reserve_commit_diff = | |
1545 | (buf_trunc(offsets->begin, chan) | |
1546 | >> chan->backend.num_subbuf_order) | |
1547 | - ((unsigned long) v_read(config, | |
1548 | &buf->commit_cold[sb_index].cc_sb) | |
1549 | & chan->commit_count_mask); | |
1550 | if (likely(reserve_commit_diff == 0)) { | |
1551 | /* Next subbuffer not being written to. */ | |
1552 | if (unlikely(config->mode != RING_BUFFER_OVERWRITE && | |
1553 | subbuf_trunc(offsets->begin, chan) | |
1554 | - subbuf_trunc((unsigned long) | |
1555 | atomic_long_read(&buf->consumed), chan) | |
1556 | >= chan->backend.buf_size)) { | |
1557 | /* | |
1558 | * We do not overwrite non consumed buffers | |
1559 | * and we are full : record is lost. | |
1560 | */ | |
1561 | v_inc(config, &buf->records_lost_full); | |
1562 | return -ENOBUFS; | |
1563 | } else { | |
1564 | /* | |
1565 | * Next subbuffer not being written to, and we | |
1566 | * are either in overwrite mode or the buffer is | |
1567 | * not full. It's safe to write in this new | |
1568 | * subbuffer. | |
1569 | */ | |
1570 | } | |
1571 | } else { | |
1572 | /* | |
1573 | * Next subbuffer reserve offset does not match the | |
1574 | * commit offset. Drop record in producer-consumer and | |
1575 | * overwrite mode. Caused by either a writer OOPS or too | |
1576 | * many nested writes over a reserve/commit pair. | |
1577 | */ | |
1578 | v_inc(config, &buf->records_lost_wrap); | |
1579 | return -EIO; | |
1580 | } | |
1581 | offsets->size = | |
1582 | config->cb.record_header_size(config, chan, | |
1583 | offsets->begin, | |
1584 | &offsets->pre_header_padding, | |
1585 | ctx); | |
1586 | offsets->size += | |
1587 | lib_ring_buffer_align(offsets->begin + offsets->size, | |
1588 | ctx->largest_align) | |
1589 | + ctx->data_size; | |
1590 | if (unlikely(subbuf_offset(offsets->begin, chan) | |
1591 | + offsets->size > chan->backend.subbuf_size)) { | |
1592 | /* | |
1593 | * Record too big for subbuffers, report error, don't | |
1594 | * complete the sub-buffer switch. | |
1595 | */ | |
1596 | v_inc(config, &buf->records_lost_big); | |
1597 | return -ENOSPC; | |
1598 | } else { | |
1599 | /* | |
1600 | * We just made a successful buffer switch and the | |
1601 | * record fits in the new subbuffer. Let's write. | |
1602 | */ | |
1603 | } | |
1604 | } else { | |
1605 | /* | |
1606 | * Record fits in the current buffer and we are not on a switch | |
1607 | * boundary. It's safe to write. | |
1608 | */ | |
1609 | } | |
1610 | offsets->end = offsets->begin + offsets->size; | |
1611 | ||
1612 | if (unlikely(subbuf_offset(offsets->end, chan) == 0)) { | |
1613 | /* | |
1614 | * The offset_end will fall at the very beginning of the next | |
1615 | * subbuffer. | |
1616 | */ | |
1617 | offsets->switch_new_end = 1; /* For offsets->begin */ | |
1618 | } | |
1619 | return 0; | |
1620 | } | |
1621 | ||
1622 | /** | |
1623 | * lib_ring_buffer_reserve_slow - Atomic slot reservation in a buffer. | |
1624 | * @ctx: ring buffer context. | |
1625 | * | |
1626 | * Return : -NOBUFS if not enough space, -ENOSPC if event size too large, | |
1627 | * -EIO for other errors, else returns 0. | |
1628 | * It will take care of sub-buffer switching. | |
1629 | */ | |
1630 | int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx) | |
1631 | { | |
1632 | struct channel *chan = ctx->chan; | |
1633 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
1634 | struct lib_ring_buffer *buf; | |
1635 | struct switch_offsets offsets; | |
1636 | int ret; | |
1637 | ||
1638 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) | |
1639 | buf = per_cpu_ptr(chan->backend.buf, ctx->cpu); | |
1640 | else | |
1641 | buf = chan->backend.buf; | |
1642 | ctx->buf = buf; | |
1643 | ||
1644 | offsets.size = 0; | |
1645 | ||
1646 | do { | |
1647 | ret = lib_ring_buffer_try_reserve_slow(buf, chan, &offsets, | |
1648 | ctx); | |
1649 | if (unlikely(ret)) | |
1650 | return ret; | |
1651 | } while (unlikely(v_cmpxchg(config, &buf->offset, offsets.old, | |
1652 | offsets.end) | |
1653 | != offsets.old)); | |
1654 | ||
1655 | /* | |
1656 | * Atomically update last_tsc. This update races against concurrent | |
1657 | * atomic updates, but the race will always cause supplementary full TSC | |
1658 | * records, never the opposite (missing a full TSC record when it would | |
1659 | * be needed). | |
1660 | */ | |
1661 | save_last_tsc(config, buf, ctx->tsc); | |
1662 | ||
1663 | /* | |
1664 | * Push the reader if necessary | |
1665 | */ | |
1666 | lib_ring_buffer_reserve_push_reader(buf, chan, offsets.end - 1); | |
1667 | ||
1668 | /* | |
1669 | * Clear noref flag for this subbuffer. | |
1670 | */ | |
1671 | lib_ring_buffer_clear_noref(config, &buf->backend, | |
1672 | subbuf_index(offsets.end - 1, chan)); | |
1673 | ||
1674 | /* | |
1675 | * Switch old subbuffer if needed. | |
1676 | */ | |
1677 | if (unlikely(offsets.switch_old_end)) { | |
1678 | lib_ring_buffer_clear_noref(config, &buf->backend, | |
1679 | subbuf_index(offsets.old - 1, chan)); | |
1680 | lib_ring_buffer_switch_old_end(buf, chan, &offsets, ctx->tsc); | |
1681 | } | |
1682 | ||
1683 | /* | |
1684 | * Populate new subbuffer. | |
1685 | */ | |
1686 | if (unlikely(offsets.switch_new_start)) | |
1687 | lib_ring_buffer_switch_new_start(buf, chan, &offsets, ctx->tsc); | |
1688 | ||
1689 | if (unlikely(offsets.switch_new_end)) | |
1690 | lib_ring_buffer_switch_new_end(buf, chan, &offsets, ctx->tsc); | |
1691 | ||
1692 | ctx->slot_size = offsets.size; | |
1693 | ctx->pre_offset = offsets.begin; | |
1694 | ctx->buf_offset = offsets.begin + offsets.pre_header_padding; | |
1695 | return 0; | |
1696 | } | |
1697 | EXPORT_SYMBOL_GPL(lib_ring_buffer_reserve_slow); |