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 | |
0466ac28 MD |
20 | #include <lttng/ringbuffer-context.h> |
21 | #include "ringbuffer-config.h" | |
4931a13e MD |
22 | #include "backend_types.h" |
23 | #include "frontend_types.h" | |
a6352fd4 | 24 | #include "shm.h" |
852c2936 MD |
25 | |
26 | /* Buffer offset macros */ | |
27 | ||
28 | /* buf_trunc mask selects only the buffer number. */ | |
29 | static inline | |
5198080d MJ |
30 | unsigned long buf_trunc(unsigned long offset, |
31 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
32 | { |
33 | return offset & ~(chan->backend.buf_size - 1); | |
34 | ||
35 | } | |
36 | ||
37 | /* Select the buffer number value (counter). */ | |
38 | static inline | |
5198080d MJ |
39 | unsigned long buf_trunc_val(unsigned long offset, |
40 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
41 | { |
42 | return buf_trunc(offset, chan) >> chan->backend.buf_size_order; | |
43 | } | |
44 | ||
45 | /* buf_offset mask selects only the offset within the current buffer. */ | |
46 | static inline | |
5198080d MJ |
47 | unsigned long buf_offset(unsigned long offset, |
48 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
49 | { |
50 | return offset & (chan->backend.buf_size - 1); | |
51 | } | |
52 | ||
53 | /* subbuf_offset mask selects the offset within the current subbuffer. */ | |
54 | static inline | |
5198080d MJ |
55 | unsigned long subbuf_offset(unsigned long offset, |
56 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
57 | { |
58 | return offset & (chan->backend.subbuf_size - 1); | |
59 | } | |
60 | ||
61 | /* subbuf_trunc mask selects the subbuffer number. */ | |
62 | static inline | |
5198080d MJ |
63 | unsigned long subbuf_trunc(unsigned long offset, |
64 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
65 | { |
66 | return offset & ~(chan->backend.subbuf_size - 1); | |
67 | } | |
68 | ||
69 | /* subbuf_align aligns the offset to the next subbuffer. */ | |
70 | static inline | |
5198080d MJ |
71 | unsigned long subbuf_align(unsigned long offset, |
72 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
73 | { |
74 | return (offset + chan->backend.subbuf_size) | |
75 | & ~(chan->backend.subbuf_size - 1); | |
76 | } | |
77 | ||
78 | /* subbuf_index returns the index of the current subbuffer within the buffer. */ | |
79 | static inline | |
5198080d MJ |
80 | unsigned long subbuf_index(unsigned long offset, |
81 | struct lttng_ust_lib_ring_buffer_channel *chan) | |
852c2936 MD |
82 | { |
83 | return buf_offset(offset, chan) >> chan->backend.subbuf_size_order; | |
84 | } | |
85 | ||
86 | /* | |
87 | * Last TSC comparison functions. Check if the current TSC overflows tsc_bits | |
88 | * bits from the last TSC read. When overflows are detected, the full 64-bit | |
89 | * timestamp counter should be written in the record header. Reads and writes | |
90 | * last_tsc atomically. | |
91 | */ | |
92 | ||
14641deb | 93 | #if (CAA_BITS_PER_LONG == 32) |
852c2936 | 94 | static inline |
4cfec15c | 95 | void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 96 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
97 | { |
98 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
99 | return; | |
100 | ||
101 | /* | |
102 | * Ensure the compiler performs this update in a single instruction. | |
103 | */ | |
104 | v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits)); | |
105 | } | |
106 | ||
107 | static inline | |
4cfec15c | 108 | int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 109 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
110 | { |
111 | unsigned long tsc_shifted; | |
112 | ||
113 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
114 | return 0; | |
115 | ||
116 | tsc_shifted = (unsigned long)(tsc >> config->tsc_bits); | |
b5a3dfa5 | 117 | if (caa_unlikely(tsc_shifted |
852c2936 MD |
118 | - (unsigned long)v_read(config, &buf->last_tsc))) |
119 | return 1; | |
120 | else | |
121 | return 0; | |
122 | } | |
123 | #else | |
124 | static inline | |
4cfec15c | 125 | void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 126 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
127 | { |
128 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
129 | return; | |
130 | ||
131 | v_set(config, &buf->last_tsc, (unsigned long)tsc); | |
132 | } | |
133 | ||
134 | static inline | |
4cfec15c | 135 | int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 136 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
137 | { |
138 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
139 | return 0; | |
140 | ||
b5a3dfa5 | 141 | if (caa_unlikely((tsc - v_read(config, &buf->last_tsc)) |
852c2936 MD |
142 | >> config->tsc_bits)) |
143 | return 1; | |
144 | else | |
145 | return 0; | |
146 | } | |
147 | #endif | |
148 | ||
ddabe860 | 149 | __attribute__((visibility("hidden"))) |
852c2936 | 150 | extern |
e56bb47c MD |
151 | int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx, |
152 | void *client_ctx); | |
852c2936 | 153 | |
ddabe860 | 154 | __attribute__((visibility("hidden"))) |
852c2936 | 155 | extern |
4cfec15c | 156 | void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf, |
1d498196 | 157 | enum switch_mode mode, |
38fae1d3 | 158 | struct lttng_ust_shm_handle *handle); |
852c2936 | 159 | |
ddabe860 | 160 | __attribute__((visibility("hidden"))) |
b07cd987 MD |
161 | void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_lib_ring_buffer_config *config, |
162 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 163 | struct lttng_ust_lib_ring_buffer_channel *chan, |
b07cd987 MD |
164 | unsigned long offset, |
165 | unsigned long commit_count, | |
166 | unsigned long idx, | |
167 | struct lttng_ust_shm_handle *handle, | |
168 | uint64_t tsc); | |
169 | ||
852c2936 MD |
170 | /* Buffer write helpers */ |
171 | ||
172 | static inline | |
4cfec15c | 173 | void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf, |
5198080d | 174 | struct lttng_ust_lib_ring_buffer_channel *chan, |
852c2936 MD |
175 | unsigned long offset) |
176 | { | |
177 | unsigned long consumed_old, consumed_new; | |
178 | ||
179 | do { | |
14641deb | 180 | consumed_old = uatomic_read(&buf->consumed); |
852c2936 MD |
181 | /* |
182 | * If buffer is in overwrite mode, push the reader consumed | |
183 | * count if the write position has reached it and we are not | |
184 | * at the first iteration (don't push the reader farther than | |
185 | * the writer). This operation can be done concurrently by many | |
186 | * writers in the same buffer, the writer being at the farthest | |
187 | * write position sub-buffer index in the buffer being the one | |
188 | * which will win this loop. | |
189 | */ | |
b5a3dfa5 | 190 | if (caa_unlikely(subbuf_trunc(offset, chan) |
852c2936 MD |
191 | - subbuf_trunc(consumed_old, chan) |
192 | >= chan->backend.buf_size)) | |
193 | consumed_new = subbuf_align(consumed_old, chan); | |
194 | else | |
195 | return; | |
b5a3dfa5 | 196 | } while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old, |
852c2936 MD |
197 | consumed_new) != consumed_old)); |
198 | } | |
199 | ||
4c742ffd MD |
200 | /* |
201 | * Move consumed position to the beginning of subbuffer in which the | |
202 | * write offset is. Should only be used on ring buffers that are not | |
203 | * actively being written into, because clear_reader does not take into | |
204 | * account the commit counters when moving the consumed position, which | |
205 | * can make concurrent trace producers or consumers observe consumed | |
206 | * position further than the write offset, which breaks ring buffer | |
207 | * algorithm guarantees. | |
208 | */ | |
beca55a1 MD |
209 | static inline |
210 | void lib_ring_buffer_clear_reader(struct lttng_ust_lib_ring_buffer *buf, | |
211 | struct lttng_ust_shm_handle *handle) | |
212 | { | |
5198080d | 213 | struct lttng_ust_lib_ring_buffer_channel *chan; |
beca55a1 MD |
214 | const struct lttng_ust_lib_ring_buffer_config *config; |
215 | unsigned long offset, consumed_old, consumed_new; | |
216 | ||
217 | chan = shmp(handle, buf->backend.chan); | |
218 | if (!chan) | |
219 | return; | |
220 | config = &chan->backend.config; | |
221 | ||
222 | do { | |
223 | offset = v_read(config, &buf->offset); | |
224 | consumed_old = uatomic_read(&buf->consumed); | |
4c742ffd MD |
225 | CHAN_WARN_ON(chan, (long) (subbuf_trunc(offset, chan) |
226 | - subbuf_trunc(consumed_old, chan)) | |
227 | < 0); | |
228 | consumed_new = subbuf_trunc(offset, chan); | |
beca55a1 MD |
229 | } while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old, |
230 | consumed_new) != consumed_old)); | |
231 | } | |
232 | ||
852c2936 | 233 | static inline |
4cfec15c MD |
234 | int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config, |
235 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 236 | struct lttng_ust_lib_ring_buffer_channel *chan) |
852c2936 MD |
237 | { |
238 | return !!subbuf_offset(v_read(config, &buf->offset), chan); | |
239 | } | |
240 | ||
241 | static inline | |
4cfec15c MD |
242 | unsigned long lib_ring_buffer_get_data_size(const struct lttng_ust_lib_ring_buffer_config *config, |
243 | struct lttng_ust_lib_ring_buffer *buf, | |
1d498196 | 244 | unsigned long idx, |
38fae1d3 | 245 | struct lttng_ust_shm_handle *handle) |
852c2936 | 246 | { |
1d498196 | 247 | return subbuffer_get_data_size(config, &buf->backend, idx, handle); |
852c2936 MD |
248 | } |
249 | ||
250 | /* | |
251 | * Check if all space reservation in a buffer have been committed. This helps | |
252 | * knowing if an execution context is nested (for per-cpu buffers only). | |
253 | * This is a very specific ftrace use-case, so we keep this as "internal" API. | |
254 | */ | |
255 | static inline | |
4cfec15c MD |
256 | int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_config *config, |
257 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 258 | struct lttng_ust_lib_ring_buffer_channel *chan, |
38fae1d3 | 259 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
260 | { |
261 | unsigned long offset, idx, commit_count; | |
730be651 | 262 | struct commit_counters_hot *cc_hot; |
852c2936 MD |
263 | |
264 | CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU); | |
265 | CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU); | |
266 | ||
267 | /* | |
268 | * Read offset and commit count in a loop so they are both read | |
269 | * atomically wrt interrupts. By deal with interrupt concurrency by | |
270 | * restarting both reads if the offset has been pushed. Note that given | |
271 | * we only have to deal with interrupt concurrency here, an interrupt | |
272 | * modifying the commit count will also modify "offset", so it is safe | |
273 | * to only check for offset modifications. | |
274 | */ | |
275 | do { | |
276 | offset = v_read(config, &buf->offset); | |
277 | idx = subbuf_index(offset, chan); | |
730be651 MD |
278 | cc_hot = shmp_index(handle, buf->commit_hot, idx); |
279 | if (caa_unlikely(!cc_hot)) | |
280 | return 0; | |
15500a1b | 281 | commit_count = v_read(config, &cc_hot->cc); |
852c2936 MD |
282 | } while (offset != v_read(config, &buf->offset)); |
283 | ||
284 | return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) | |
285 | - (commit_count & chan->commit_count_mask) == 0); | |
286 | } | |
287 | ||
1b7b0501 MD |
288 | /* |
289 | * Receive end of subbuffer TSC as parameter. It has been read in the | |
290 | * space reservation loop of either reserve or switch, which ensures it | |
291 | * progresses monotonically with event records in the buffer. Therefore, | |
292 | * it ensures that the end timestamp of a subbuffer is <= begin | |
293 | * timestamp of the following subbuffers. | |
294 | */ | |
852c2936 | 295 | static inline |
4cfec15c MD |
296 | void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config, |
297 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 298 | struct lttng_ust_lib_ring_buffer_channel *chan, |
852c2936 MD |
299 | unsigned long offset, |
300 | unsigned long commit_count, | |
1d498196 | 301 | unsigned long idx, |
1b7b0501 MD |
302 | struct lttng_ust_shm_handle *handle, |
303 | uint64_t tsc) | |
852c2936 MD |
304 | { |
305 | unsigned long old_commit_count = commit_count | |
306 | - chan->backend.subbuf_size; | |
852c2936 MD |
307 | |
308 | /* Check if all commits have been done */ | |
b5a3dfa5 | 309 | if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) |
b07cd987 MD |
310 | - (old_commit_count & chan->commit_count_mask) == 0)) |
311 | lib_ring_buffer_check_deliver_slow(config, buf, chan, offset, | |
312 | commit_count, idx, handle, tsc); | |
852c2936 MD |
313 | } |
314 | ||
315 | /* | |
316 | * lib_ring_buffer_write_commit_counter | |
317 | * | |
318 | * For flight recording. must be called after commit. | |
319 | * This function increments the subbuffer's commit_seq counter each time the | |
320 | * commit count reaches back the reserve offset (modulo subbuffer size). It is | |
321 | * useful for crash dump. | |
322 | */ | |
323 | static inline | |
4cfec15c MD |
324 | void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer_config *config, |
325 | struct lttng_ust_lib_ring_buffer *buf, | |
5198080d | 326 | struct lttng_ust_lib_ring_buffer_channel *chan, |
852c2936 MD |
327 | unsigned long buf_offset, |
328 | unsigned long commit_count, | |
d2fe4771 MD |
329 | struct lttng_ust_shm_handle *handle, |
330 | struct commit_counters_hot *cc_hot) | |
852c2936 | 331 | { |
80249235 | 332 | unsigned long commit_seq_old; |
852c2936 MD |
333 | |
334 | if (config->oops != RING_BUFFER_OOPS_CONSISTENCY) | |
335 | return; | |
336 | ||
852c2936 MD |
337 | /* |
338 | * subbuf_offset includes commit_count_mask. We can simply | |
339 | * compare the offsets within the subbuffer without caring about | |
340 | * buffer full/empty mismatch because offset is never zero here | |
341 | * (subbuffer header and record headers have non-zero length). | |
342 | */ | |
80249235 | 343 | if (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan))) |
852c2936 MD |
344 | return; |
345 | ||
d2fe4771 | 346 | commit_seq_old = v_read(config, &cc_hot->seq); |
16ec84c8 | 347 | if (caa_likely((long) (commit_seq_old - commit_count) < 0)) |
d2fe4771 | 348 | v_set(config, &cc_hot->seq, commit_count); |
852c2936 MD |
349 | } |
350 | ||
ddabe860 | 351 | __attribute__((visibility("hidden"))) |
4cfec15c | 352 | extern int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf, |
a6352fd4 | 353 | struct channel_backend *chanb, int cpu, |
38fae1d3 | 354 | struct lttng_ust_shm_handle *handle, |
1d498196 | 355 | struct shm_object *shmobj); |
ddabe860 MJ |
356 | |
357 | __attribute__((visibility("hidden"))) | |
4cfec15c | 358 | extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf, |
38fae1d3 | 359 | struct lttng_ust_shm_handle *handle); |
852c2936 MD |
360 | |
361 | /* Keep track of trap nesting inside ring buffer code */ | |
ddabe860 | 362 | __attribute__((visibility("hidden"))) |
8c90a710 | 363 | extern DECLARE_URCU_TLS(unsigned int, lib_ring_buffer_nesting); |
852c2936 | 364 | |
e92f3e28 | 365 | #endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */ |