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e92f3e28 MD |
1 | #ifndef _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H |
2 | #define _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H | |
852c2936 MD |
3 | |
4 | /* | |
e92f3e28 | 5 | * libringbuffer/frontend_internal.h |
852c2936 MD |
6 | * |
7 | * Ring Buffer Library Synchronization Header (internal helpers). | |
8 | * | |
e92f3e28 MD |
9 | * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
10 | * | |
11 | * This library is free software; you can redistribute it and/or | |
12 | * modify it under the terms of the GNU Lesser General Public | |
13 | * License as published by the Free Software Foundation; only | |
14 | * version 2.1 of the License. | |
15 | * | |
16 | * This library is distributed in the hope that it will be useful, | |
17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
19 | * Lesser General Public License for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU Lesser General Public | |
22 | * License along with this library; if not, write to the Free Software | |
23 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
24 | * | |
25 | * | |
852c2936 MD |
26 | * Author: |
27 | * Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
28 | * | |
29 | * See ring_buffer_frontend.c for more information on wait-free algorithms. | |
30 | * | |
31 | * Dual LGPL v2.1/GPL v2 license. | |
32 | */ | |
33 | ||
14641deb | 34 | #include <urcu/compiler.h> |
8c90a710 | 35 | #include <urcu/tls-compat.h> |
2c44f5b9 MD |
36 | #include <signal.h> |
37 | #include <pthread.h> | |
14641deb | 38 | |
4318ae1b | 39 | #include <lttng/ringbuffer-config.h> |
4931a13e MD |
40 | #include "backend_types.h" |
41 | #include "frontend_types.h" | |
a6352fd4 | 42 | #include "shm.h" |
852c2936 MD |
43 | |
44 | /* Buffer offset macros */ | |
45 | ||
46 | /* buf_trunc mask selects only the buffer number. */ | |
47 | static inline | |
48 | unsigned long buf_trunc(unsigned long offset, struct channel *chan) | |
49 | { | |
50 | return offset & ~(chan->backend.buf_size - 1); | |
51 | ||
52 | } | |
53 | ||
54 | /* Select the buffer number value (counter). */ | |
55 | static inline | |
56 | unsigned long buf_trunc_val(unsigned long offset, struct channel *chan) | |
57 | { | |
58 | return buf_trunc(offset, chan) >> chan->backend.buf_size_order; | |
59 | } | |
60 | ||
61 | /* buf_offset mask selects only the offset within the current buffer. */ | |
62 | static inline | |
63 | unsigned long buf_offset(unsigned long offset, struct channel *chan) | |
64 | { | |
65 | return offset & (chan->backend.buf_size - 1); | |
66 | } | |
67 | ||
68 | /* subbuf_offset mask selects the offset within the current subbuffer. */ | |
69 | static inline | |
70 | unsigned long subbuf_offset(unsigned long offset, struct channel *chan) | |
71 | { | |
72 | return offset & (chan->backend.subbuf_size - 1); | |
73 | } | |
74 | ||
75 | /* subbuf_trunc mask selects the subbuffer number. */ | |
76 | static inline | |
77 | unsigned long subbuf_trunc(unsigned long offset, struct channel *chan) | |
78 | { | |
79 | return offset & ~(chan->backend.subbuf_size - 1); | |
80 | } | |
81 | ||
82 | /* subbuf_align aligns the offset to the next subbuffer. */ | |
83 | static inline | |
84 | unsigned long subbuf_align(unsigned long offset, struct channel *chan) | |
85 | { | |
86 | return (offset + chan->backend.subbuf_size) | |
87 | & ~(chan->backend.subbuf_size - 1); | |
88 | } | |
89 | ||
90 | /* subbuf_index returns the index of the current subbuffer within the buffer. */ | |
91 | static inline | |
92 | unsigned long subbuf_index(unsigned long offset, struct channel *chan) | |
93 | { | |
94 | return buf_offset(offset, chan) >> chan->backend.subbuf_size_order; | |
95 | } | |
96 | ||
97 | /* | |
98 | * Last TSC comparison functions. Check if the current TSC overflows tsc_bits | |
99 | * bits from the last TSC read. When overflows are detected, the full 64-bit | |
100 | * timestamp counter should be written in the record header. Reads and writes | |
101 | * last_tsc atomically. | |
102 | */ | |
103 | ||
14641deb | 104 | #if (CAA_BITS_PER_LONG == 32) |
852c2936 | 105 | static inline |
4cfec15c | 106 | void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 107 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
108 | { |
109 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
110 | return; | |
111 | ||
112 | /* | |
113 | * Ensure the compiler performs this update in a single instruction. | |
114 | */ | |
115 | v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits)); | |
116 | } | |
117 | ||
118 | static inline | |
4cfec15c | 119 | int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 120 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
121 | { |
122 | unsigned long tsc_shifted; | |
123 | ||
124 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
125 | return 0; | |
126 | ||
127 | tsc_shifted = (unsigned long)(tsc >> config->tsc_bits); | |
b5a3dfa5 | 128 | if (caa_unlikely(tsc_shifted |
852c2936 MD |
129 | - (unsigned long)v_read(config, &buf->last_tsc))) |
130 | return 1; | |
131 | else | |
132 | return 0; | |
133 | } | |
134 | #else | |
135 | static inline | |
4cfec15c | 136 | void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 137 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
138 | { |
139 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
140 | return; | |
141 | ||
142 | v_set(config, &buf->last_tsc, (unsigned long)tsc); | |
143 | } | |
144 | ||
145 | static inline | |
4cfec15c | 146 | int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 147 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
148 | { |
149 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
150 | return 0; | |
151 | ||
b5a3dfa5 | 152 | if (caa_unlikely((tsc - v_read(config, &buf->last_tsc)) |
852c2936 MD |
153 | >> config->tsc_bits)) |
154 | return 1; | |
155 | else | |
156 | return 0; | |
157 | } | |
158 | #endif | |
159 | ||
160 | extern | |
4cfec15c | 161 | int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx); |
852c2936 MD |
162 | |
163 | extern | |
4cfec15c | 164 | void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf, |
1d498196 | 165 | enum switch_mode mode, |
38fae1d3 | 166 | struct lttng_ust_shm_handle *handle); |
852c2936 | 167 | |
b07cd987 MD |
168 | void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_lib_ring_buffer_config *config, |
169 | struct lttng_ust_lib_ring_buffer *buf, | |
170 | struct channel *chan, | |
171 | unsigned long offset, | |
172 | unsigned long commit_count, | |
173 | unsigned long idx, | |
174 | struct lttng_ust_shm_handle *handle, | |
175 | uint64_t tsc); | |
176 | ||
852c2936 MD |
177 | /* Buffer write helpers */ |
178 | ||
179 | static inline | |
4cfec15c | 180 | void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf, |
852c2936 MD |
181 | struct channel *chan, |
182 | unsigned long offset) | |
183 | { | |
184 | unsigned long consumed_old, consumed_new; | |
185 | ||
186 | do { | |
14641deb | 187 | consumed_old = uatomic_read(&buf->consumed); |
852c2936 MD |
188 | /* |
189 | * If buffer is in overwrite mode, push the reader consumed | |
190 | * count if the write position has reached it and we are not | |
191 | * at the first iteration (don't push the reader farther than | |
192 | * the writer). This operation can be done concurrently by many | |
193 | * writers in the same buffer, the writer being at the farthest | |
194 | * write position sub-buffer index in the buffer being the one | |
195 | * which will win this loop. | |
196 | */ | |
b5a3dfa5 | 197 | if (caa_unlikely(subbuf_trunc(offset, chan) |
852c2936 MD |
198 | - subbuf_trunc(consumed_old, chan) |
199 | >= chan->backend.buf_size)) | |
200 | consumed_new = subbuf_align(consumed_old, chan); | |
201 | else | |
202 | return; | |
b5a3dfa5 | 203 | } while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old, |
852c2936 MD |
204 | consumed_new) != consumed_old)); |
205 | } | |
206 | ||
852c2936 | 207 | static inline |
4cfec15c MD |
208 | int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config, |
209 | struct lttng_ust_lib_ring_buffer *buf, | |
852c2936 MD |
210 | struct channel *chan) |
211 | { | |
212 | return !!subbuf_offset(v_read(config, &buf->offset), chan); | |
213 | } | |
214 | ||
215 | static inline | |
4cfec15c MD |
216 | unsigned long lib_ring_buffer_get_data_size(const struct lttng_ust_lib_ring_buffer_config *config, |
217 | struct lttng_ust_lib_ring_buffer *buf, | |
1d498196 | 218 | unsigned long idx, |
38fae1d3 | 219 | struct lttng_ust_shm_handle *handle) |
852c2936 | 220 | { |
1d498196 | 221 | return subbuffer_get_data_size(config, &buf->backend, idx, handle); |
852c2936 MD |
222 | } |
223 | ||
224 | /* | |
225 | * Check if all space reservation in a buffer have been committed. This helps | |
226 | * knowing if an execution context is nested (for per-cpu buffers only). | |
227 | * This is a very specific ftrace use-case, so we keep this as "internal" API. | |
228 | */ | |
229 | static inline | |
4cfec15c MD |
230 | int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_config *config, |
231 | struct lttng_ust_lib_ring_buffer *buf, | |
1d498196 | 232 | struct channel *chan, |
38fae1d3 | 233 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
234 | { |
235 | unsigned long offset, idx, commit_count; | |
15500a1b | 236 | struct commit_counters_hot *cc_hot = shmp_index(handle, buf->commit_hot, idx); |
852c2936 MD |
237 | |
238 | CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU); | |
239 | CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU); | |
240 | ||
15500a1b MD |
241 | if (caa_unlikely(!cc_hot)) |
242 | return 0; | |
243 | ||
852c2936 MD |
244 | /* |
245 | * Read offset and commit count in a loop so they are both read | |
246 | * atomically wrt interrupts. By deal with interrupt concurrency by | |
247 | * restarting both reads if the offset has been pushed. Note that given | |
248 | * we only have to deal with interrupt concurrency here, an interrupt | |
249 | * modifying the commit count will also modify "offset", so it is safe | |
250 | * to only check for offset modifications. | |
251 | */ | |
252 | do { | |
253 | offset = v_read(config, &buf->offset); | |
254 | idx = subbuf_index(offset, chan); | |
15500a1b | 255 | commit_count = v_read(config, &cc_hot->cc); |
852c2936 MD |
256 | } while (offset != v_read(config, &buf->offset)); |
257 | ||
258 | return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) | |
259 | - (commit_count & chan->commit_count_mask) == 0); | |
260 | } | |
261 | ||
1b7b0501 MD |
262 | /* |
263 | * Receive end of subbuffer TSC as parameter. It has been read in the | |
264 | * space reservation loop of either reserve or switch, which ensures it | |
265 | * progresses monotonically with event records in the buffer. Therefore, | |
266 | * it ensures that the end timestamp of a subbuffer is <= begin | |
267 | * timestamp of the following subbuffers. | |
268 | */ | |
852c2936 | 269 | static inline |
4cfec15c MD |
270 | void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config, |
271 | struct lttng_ust_lib_ring_buffer *buf, | |
852c2936 MD |
272 | struct channel *chan, |
273 | unsigned long offset, | |
274 | unsigned long commit_count, | |
1d498196 | 275 | unsigned long idx, |
1b7b0501 MD |
276 | struct lttng_ust_shm_handle *handle, |
277 | uint64_t tsc) | |
852c2936 MD |
278 | { |
279 | unsigned long old_commit_count = commit_count | |
280 | - chan->backend.subbuf_size; | |
852c2936 MD |
281 | |
282 | /* Check if all commits have been done */ | |
b5a3dfa5 | 283 | if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) |
b07cd987 MD |
284 | - (old_commit_count & chan->commit_count_mask) == 0)) |
285 | lib_ring_buffer_check_deliver_slow(config, buf, chan, offset, | |
286 | commit_count, idx, handle, tsc); | |
852c2936 MD |
287 | } |
288 | ||
289 | /* | |
290 | * lib_ring_buffer_write_commit_counter | |
291 | * | |
292 | * For flight recording. must be called after commit. | |
293 | * This function increments the subbuffer's commit_seq counter each time the | |
294 | * commit count reaches back the reserve offset (modulo subbuffer size). It is | |
295 | * useful for crash dump. | |
296 | */ | |
297 | static inline | |
4cfec15c MD |
298 | void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer_config *config, |
299 | struct lttng_ust_lib_ring_buffer *buf, | |
852c2936 | 300 | struct channel *chan, |
852c2936 MD |
301 | unsigned long buf_offset, |
302 | unsigned long commit_count, | |
d2fe4771 MD |
303 | struct lttng_ust_shm_handle *handle, |
304 | struct commit_counters_hot *cc_hot) | |
852c2936 | 305 | { |
80249235 | 306 | unsigned long commit_seq_old; |
852c2936 MD |
307 | |
308 | if (config->oops != RING_BUFFER_OOPS_CONSISTENCY) | |
309 | return; | |
310 | ||
852c2936 MD |
311 | /* |
312 | * subbuf_offset includes commit_count_mask. We can simply | |
313 | * compare the offsets within the subbuffer without caring about | |
314 | * buffer full/empty mismatch because offset is never zero here | |
315 | * (subbuffer header and record headers have non-zero length). | |
316 | */ | |
80249235 | 317 | if (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan))) |
852c2936 MD |
318 | return; |
319 | ||
d2fe4771 | 320 | commit_seq_old = v_read(config, &cc_hot->seq); |
16ec84c8 | 321 | if (caa_likely((long) (commit_seq_old - commit_count) < 0)) |
d2fe4771 | 322 | v_set(config, &cc_hot->seq, commit_count); |
852c2936 MD |
323 | } |
324 | ||
4cfec15c | 325 | extern int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf, |
a6352fd4 | 326 | struct channel_backend *chanb, int cpu, |
38fae1d3 | 327 | struct lttng_ust_shm_handle *handle, |
1d498196 | 328 | struct shm_object *shmobj); |
4cfec15c | 329 | extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf, |
38fae1d3 | 330 | struct lttng_ust_shm_handle *handle); |
852c2936 MD |
331 | |
332 | /* Keep track of trap nesting inside ring buffer code */ | |
8c90a710 | 333 | extern DECLARE_URCU_TLS(unsigned int, lib_ring_buffer_nesting); |
852c2936 | 334 | |
e92f3e28 | 335 | #endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */ |