Commit | Line | Data |
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852c2936 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: (LGPL-2.1-only or GPL-2.0-only) |
852c2936 | 3 | * |
e92f3e28 MD |
4 | * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
5 | * | |
c0c0989a | 6 | * Ring Buffer Library Synchronization Header (internal helpers). |
852c2936 MD |
7 | * |
8 | * See ring_buffer_frontend.c for more information on wait-free algorithms. | |
852c2936 MD |
9 | */ |
10 | ||
c0c0989a MJ |
11 | #ifndef _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H |
12 | #define _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H | |
13 | ||
14641deb | 14 | #include <urcu/compiler.h> |
8c90a710 | 15 | #include <urcu/tls-compat.h> |
2c44f5b9 | 16 | #include <signal.h> |
fb31eb73 | 17 | #include <stdint.h> |
2c44f5b9 | 18 | #include <pthread.h> |
14641deb | 19 | |
4318ae1b | 20 | #include <lttng/ringbuffer-config.h> |
4931a13e MD |
21 | #include "backend_types.h" |
22 | #include "frontend_types.h" | |
a6352fd4 | 23 | #include "shm.h" |
852c2936 MD |
24 | |
25 | /* Buffer offset macros */ | |
26 | ||
27 | /* buf_trunc mask selects only the buffer number. */ | |
28 | static inline | |
5198080d MJ |
29 | unsigned long buf_trunc(unsigned long offset, |
30 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
31 | { |
32 | return offset & ~(chan->backend.buf_size - 1); | |
33 | ||
34 | } | |
35 | ||
36 | /* Select the buffer number value (counter). */ | |
37 | static inline | |
5198080d MJ |
38 | unsigned long buf_trunc_val(unsigned long offset, |
39 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
40 | { |
41 | return buf_trunc(offset, chan) >> chan->backend.buf_size_order; | |
42 | } | |
43 | ||
44 | /* buf_offset mask selects only the offset within the current buffer. */ | |
45 | static inline | |
5198080d MJ |
46 | unsigned long buf_offset(unsigned long offset, |
47 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
48 | { |
49 | return offset & (chan->backend.buf_size - 1); | |
50 | } | |
51 | ||
52 | /* subbuf_offset mask selects the offset within the current subbuffer. */ | |
53 | static inline | |
5198080d MJ |
54 | unsigned long subbuf_offset(unsigned long offset, |
55 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
56 | { |
57 | return offset & (chan->backend.subbuf_size - 1); | |
58 | } | |
59 | ||
60 | /* subbuf_trunc mask selects the subbuffer number. */ | |
61 | static inline | |
5198080d MJ |
62 | unsigned long subbuf_trunc(unsigned long offset, |
63 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
64 | { |
65 | return offset & ~(chan->backend.subbuf_size - 1); | |
66 | } | |
67 | ||
68 | /* subbuf_align aligns the offset to the next subbuffer. */ | |
69 | static inline | |
5198080d MJ |
70 | unsigned long subbuf_align(unsigned long offset, |
71 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
72 | { |
73 | return (offset + chan->backend.subbuf_size) | |
74 | & ~(chan->backend.subbuf_size - 1); | |
75 | } | |
76 | ||
77 | /* subbuf_index returns the index of the current subbuffer within the buffer. */ | |
78 | static inline | |
5198080d MJ |
79 | unsigned long subbuf_index(unsigned long offset, |
80 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
81 | { |
82 | return buf_offset(offset, chan) >> chan->backend.subbuf_size_order; | |
83 | } | |
84 | ||
85 | /* | |
86 | * Last TSC comparison functions. Check if the current TSC overflows tsc_bits | |
87 | * bits from the last TSC read. When overflows are detected, the full 64-bit | |
88 | * timestamp counter should be written in the record header. Reads and writes | |
89 | * last_tsc atomically. | |
90 | */ | |
91 | ||
14641deb | 92 | #if (CAA_BITS_PER_LONG == 32) |
852c2936 | 93 | static inline |
4cfec15c | 94 | void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 95 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
96 | { |
97 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
98 | return; | |
99 | ||
100 | /* | |
101 | * Ensure the compiler performs this update in a single instruction. | |
102 | */ | |
103 | v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits)); | |
104 | } | |
105 | ||
106 | static inline | |
4cfec15c | 107 | int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 108 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
109 | { |
110 | unsigned long tsc_shifted; | |
111 | ||
112 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
113 | return 0; | |
114 | ||
115 | tsc_shifted = (unsigned long)(tsc >> config->tsc_bits); | |
b5a3dfa5 | 116 | if (caa_unlikely(tsc_shifted |
852c2936 MD |
117 | - (unsigned long)v_read(config, &buf->last_tsc))) |
118 | return 1; | |
119 | else | |
120 | return 0; | |
121 | } | |
122 | #else | |
123 | static inline | |
4cfec15c | 124 | void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 125 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
126 | { |
127 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
128 | return; | |
129 | ||
130 | v_set(config, &buf->last_tsc, (unsigned long)tsc); | |
131 | } | |
132 | ||
133 | static inline | |
4cfec15c | 134 | int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 135 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
136 | { |
137 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
138 | return 0; | |
139 | ||
b5a3dfa5 | 140 | if (caa_unlikely((tsc - v_read(config, &buf->last_tsc)) |
852c2936 MD |
141 | >> config->tsc_bits)) |
142 | return 1; | |
143 | else | |
144 | return 0; | |
145 | } | |
146 | #endif | |
147 | ||
ddabe860 | 148 | __attribute__((visibility("hidden"))) |
852c2936 | 149 | extern |
e56bb47c MD |
150 | int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx, |
151 | void *client_ctx); | |
852c2936 | 152 | |
ddabe860 | 153 | __attribute__((visibility("hidden"))) |
852c2936 | 154 | extern |
4cfec15c | 155 | void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf, |
1d498196 | 156 | enum switch_mode mode, |
38fae1d3 | 157 | struct lttng_ust_shm_handle *handle); |
852c2936 | 158 | |
ddabe860 | 159 | __attribute__((visibility("hidden"))) |
b07cd987 MD |
160 | void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_lib_ring_buffer_config *config, |
161 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 162 | struct lttng_ust_lib_ring_buffer_channel *chan, |
b07cd987 MD |
163 | unsigned long offset, |
164 | unsigned long commit_count, | |
165 | unsigned long idx, | |
166 | struct lttng_ust_shm_handle *handle, | |
167 | uint64_t tsc); | |
168 | ||
852c2936 MD |
169 | /* Buffer write helpers */ |
170 | ||
171 | static inline | |
4cfec15c | 172 | void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf, |
5198080d | 173 | struct lttng_ust_lib_ring_buffer_channel *chan, |
852c2936 MD |
174 | unsigned long offset) |
175 | { | |
176 | unsigned long consumed_old, consumed_new; | |
177 | ||
178 | do { | |
14641deb | 179 | consumed_old = uatomic_read(&buf->consumed); |
852c2936 MD |
180 | /* |
181 | * If buffer is in overwrite mode, push the reader consumed | |
182 | * count if the write position has reached it and we are not | |
183 | * at the first iteration (don't push the reader farther than | |
184 | * the writer). This operation can be done concurrently by many | |
185 | * writers in the same buffer, the writer being at the farthest | |
186 | * write position sub-buffer index in the buffer being the one | |
187 | * which will win this loop. | |
188 | */ | |
b5a3dfa5 | 189 | if (caa_unlikely(subbuf_trunc(offset, chan) |
852c2936 MD |
190 | - subbuf_trunc(consumed_old, chan) |
191 | >= chan->backend.buf_size)) | |
192 | consumed_new = subbuf_align(consumed_old, chan); | |
193 | else | |
194 | return; | |
b5a3dfa5 | 195 | } while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old, |
852c2936 MD |
196 | consumed_new) != consumed_old)); |
197 | } | |
198 | ||
4c742ffd MD |
199 | /* |
200 | * Move consumed position to the beginning of subbuffer in which the | |
201 | * write offset is. Should only be used on ring buffers that are not | |
202 | * actively being written into, because clear_reader does not take into | |
203 | * account the commit counters when moving the consumed position, which | |
204 | * can make concurrent trace producers or consumers observe consumed | |
205 | * position further than the write offset, which breaks ring buffer | |
206 | * algorithm guarantees. | |
207 | */ | |
beca55a1 MD |
208 | static inline |
209 | void lib_ring_buffer_clear_reader(struct lttng_ust_lib_ring_buffer *buf, | |
210 | struct lttng_ust_shm_handle *handle) | |
211 | { | |
5198080d | 212 | struct lttng_ust_lib_ring_buffer_channel *chan; |
beca55a1 MD |
213 | const struct lttng_ust_lib_ring_buffer_config *config; |
214 | unsigned long offset, consumed_old, consumed_new; | |
215 | ||
216 | chan = shmp(handle, buf->backend.chan); | |
217 | if (!chan) | |
218 | return; | |
219 | config = &chan->backend.config; | |
220 | ||
221 | do { | |
222 | offset = v_read(config, &buf->offset); | |
223 | consumed_old = uatomic_read(&buf->consumed); | |
4c742ffd MD |
224 | CHAN_WARN_ON(chan, (long) (subbuf_trunc(offset, chan) |
225 | - subbuf_trunc(consumed_old, chan)) | |
226 | < 0); | |
227 | consumed_new = subbuf_trunc(offset, chan); | |
beca55a1 MD |
228 | } while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old, |
229 | consumed_new) != consumed_old)); | |
230 | } | |
231 | ||
852c2936 | 232 | static inline |
4cfec15c MD |
233 | int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config, |
234 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 235 | struct lttng_ust_lib_ring_buffer_channel *chan) |
852c2936 MD |
236 | { |
237 | return !!subbuf_offset(v_read(config, &buf->offset), chan); | |
238 | } | |
239 | ||
240 | static inline | |
4cfec15c MD |
241 | unsigned long lib_ring_buffer_get_data_size(const struct lttng_ust_lib_ring_buffer_config *config, |
242 | struct lttng_ust_lib_ring_buffer *buf, | |
1d498196 | 243 | unsigned long idx, |
38fae1d3 | 244 | struct lttng_ust_shm_handle *handle) |
852c2936 | 245 | { |
1d498196 | 246 | return subbuffer_get_data_size(config, &buf->backend, idx, handle); |
852c2936 MD |
247 | } |
248 | ||
249 | /* | |
250 | * Check if all space reservation in a buffer have been committed. This helps | |
251 | * knowing if an execution context is nested (for per-cpu buffers only). | |
252 | * This is a very specific ftrace use-case, so we keep this as "internal" API. | |
253 | */ | |
254 | static inline | |
4cfec15c MD |
255 | int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_config *config, |
256 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 257 | struct lttng_ust_lib_ring_buffer_channel *chan, |
38fae1d3 | 258 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
259 | { |
260 | unsigned long offset, idx, commit_count; | |
730be651 | 261 | struct commit_counters_hot *cc_hot; |
852c2936 MD |
262 | |
263 | CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU); | |
264 | CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU); | |
265 | ||
266 | /* | |
267 | * Read offset and commit count in a loop so they are both read | |
268 | * atomically wrt interrupts. By deal with interrupt concurrency by | |
269 | * restarting both reads if the offset has been pushed. Note that given | |
270 | * we only have to deal with interrupt concurrency here, an interrupt | |
271 | * modifying the commit count will also modify "offset", so it is safe | |
272 | * to only check for offset modifications. | |
273 | */ | |
274 | do { | |
275 | offset = v_read(config, &buf->offset); | |
276 | idx = subbuf_index(offset, chan); | |
730be651 MD |
277 | cc_hot = shmp_index(handle, buf->commit_hot, idx); |
278 | if (caa_unlikely(!cc_hot)) | |
279 | return 0; | |
15500a1b | 280 | commit_count = v_read(config, &cc_hot->cc); |
852c2936 MD |
281 | } while (offset != v_read(config, &buf->offset)); |
282 | ||
283 | return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) | |
284 | - (commit_count & chan->commit_count_mask) == 0); | |
285 | } | |
286 | ||
1b7b0501 MD |
287 | /* |
288 | * Receive end of subbuffer TSC as parameter. It has been read in the | |
289 | * space reservation loop of either reserve or switch, which ensures it | |
290 | * progresses monotonically with event records in the buffer. Therefore, | |
291 | * it ensures that the end timestamp of a subbuffer is <= begin | |
292 | * timestamp of the following subbuffers. | |
293 | */ | |
852c2936 | 294 | static inline |
4cfec15c MD |
295 | void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config, |
296 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 297 | struct lttng_ust_lib_ring_buffer_channel *chan, |
852c2936 MD |
298 | unsigned long offset, |
299 | unsigned long commit_count, | |
1d498196 | 300 | unsigned long idx, |
1b7b0501 MD |
301 | struct lttng_ust_shm_handle *handle, |
302 | uint64_t tsc) | |
852c2936 MD |
303 | { |
304 | unsigned long old_commit_count = commit_count | |
305 | - chan->backend.subbuf_size; | |
852c2936 MD |
306 | |
307 | /* Check if all commits have been done */ | |
b5a3dfa5 | 308 | if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) |
b07cd987 MD |
309 | - (old_commit_count & chan->commit_count_mask) == 0)) |
310 | lib_ring_buffer_check_deliver_slow(config, buf, chan, offset, | |
311 | commit_count, idx, handle, tsc); | |
852c2936 MD |
312 | } |
313 | ||
314 | /* | |
315 | * lib_ring_buffer_write_commit_counter | |
316 | * | |
317 | * For flight recording. must be called after commit. | |
318 | * This function increments the subbuffer's commit_seq counter each time the | |
319 | * commit count reaches back the reserve offset (modulo subbuffer size). It is | |
320 | * useful for crash dump. | |
321 | */ | |
322 | static inline | |
4cfec15c MD |
323 | void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer_config *config, |
324 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 325 | struct lttng_ust_lib_ring_buffer_channel *chan, |
852c2936 MD |
326 | unsigned long buf_offset, |
327 | unsigned long commit_count, | |
d2fe4771 MD |
328 | struct lttng_ust_shm_handle *handle, |
329 | struct commit_counters_hot *cc_hot) | |
852c2936 | 330 | { |
80249235 | 331 | unsigned long commit_seq_old; |
852c2936 MD |
332 | |
333 | if (config->oops != RING_BUFFER_OOPS_CONSISTENCY) | |
334 | return; | |
335 | ||
852c2936 MD |
336 | /* |
337 | * subbuf_offset includes commit_count_mask. We can simply | |
338 | * compare the offsets within the subbuffer without caring about | |
339 | * buffer full/empty mismatch because offset is never zero here | |
340 | * (subbuffer header and record headers have non-zero length). | |
341 | */ | |
80249235 | 342 | if (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan))) |
852c2936 MD |
343 | return; |
344 | ||
d2fe4771 | 345 | commit_seq_old = v_read(config, &cc_hot->seq); |
16ec84c8 | 346 | if (caa_likely((long) (commit_seq_old - commit_count) < 0)) |
d2fe4771 | 347 | v_set(config, &cc_hot->seq, commit_count); |
852c2936 MD |
348 | } |
349 | ||
ddabe860 | 350 | __attribute__((visibility("hidden"))) |
4cfec15c | 351 | extern int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf, |
a6352fd4 | 352 | struct channel_backend *chanb, int cpu, |
38fae1d3 | 353 | struct lttng_ust_shm_handle *handle, |
1d498196 | 354 | struct shm_object *shmobj); |
ddabe860 MJ |
355 | |
356 | __attribute__((visibility("hidden"))) | |
4cfec15c | 357 | extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf, |
38fae1d3 | 358 | struct lttng_ust_shm_handle *handle); |
852c2936 MD |
359 | |
360 | /* Keep track of trap nesting inside ring buffer code */ | |
ddabe860 | 361 | __attribute__((visibility("hidden"))) |
8c90a710 | 362 | extern DECLARE_URCU_TLS(unsigned int, lib_ring_buffer_nesting); |
852c2936 | 363 | |
e92f3e28 | 364 | #endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */ |