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886d51a3 MD |
1 | #ifndef _LIB_RING_BUFFER_FRONTEND_INTERNAL_H |
2 | #define _LIB_RING_BUFFER_FRONTEND_INTERNAL_H | |
f3bc08c5 MD |
3 | |
4 | /* | |
5 | * linux/ringbuffer/frontend_internal.h | |
6 | * | |
f3bc08c5 MD |
7 | * Ring Buffer Library Synchronization Header (internal helpers). |
8 | * | |
886d51a3 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 | * | |
f3bc08c5 MD |
25 | * Author: |
26 | * Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
27 | * | |
28 | * See ring_buffer_frontend.c for more information on wait-free algorithms. | |
f3bc08c5 MD |
29 | */ |
30 | ||
5671a661 MD |
31 | #include <wrapper/ringbuffer/config.h> |
32 | #include <wrapper/ringbuffer/backend_types.h> | |
33 | #include <wrapper/ringbuffer/frontend_types.h> | |
34 | #include <lib/prio_heap/lttng_prio_heap.h> /* For per-CPU read-side iterator */ | |
f3bc08c5 MD |
35 | |
36 | /* Buffer offset macros */ | |
37 | ||
38 | /* buf_trunc mask selects only the buffer number. */ | |
39 | static inline | |
40 | unsigned long buf_trunc(unsigned long offset, struct channel *chan) | |
41 | { | |
42 | return offset & ~(chan->backend.buf_size - 1); | |
43 | ||
44 | } | |
45 | ||
46 | /* Select the buffer number value (counter). */ | |
47 | static inline | |
48 | unsigned long buf_trunc_val(unsigned long offset, struct channel *chan) | |
49 | { | |
50 | return buf_trunc(offset, chan) >> chan->backend.buf_size_order; | |
51 | } | |
52 | ||
53 | /* buf_offset mask selects only the offset within the current buffer. */ | |
54 | static inline | |
55 | unsigned long buf_offset(unsigned long offset, struct channel *chan) | |
56 | { | |
57 | return offset & (chan->backend.buf_size - 1); | |
58 | } | |
59 | ||
60 | /* subbuf_offset mask selects the offset within the current subbuffer. */ | |
61 | static inline | |
62 | unsigned long subbuf_offset(unsigned long offset, struct channel *chan) | |
63 | { | |
64 | return offset & (chan->backend.subbuf_size - 1); | |
65 | } | |
66 | ||
67 | /* subbuf_trunc mask selects the subbuffer number. */ | |
68 | static inline | |
69 | unsigned long subbuf_trunc(unsigned long offset, struct channel *chan) | |
70 | { | |
71 | return offset & ~(chan->backend.subbuf_size - 1); | |
72 | } | |
73 | ||
74 | /* subbuf_align aligns the offset to the next subbuffer. */ | |
75 | static inline | |
76 | unsigned long subbuf_align(unsigned long offset, struct channel *chan) | |
77 | { | |
78 | return (offset + chan->backend.subbuf_size) | |
79 | & ~(chan->backend.subbuf_size - 1); | |
80 | } | |
81 | ||
82 | /* subbuf_index returns the index of the current subbuffer within the buffer. */ | |
83 | static inline | |
84 | unsigned long subbuf_index(unsigned long offset, struct channel *chan) | |
85 | { | |
86 | return buf_offset(offset, chan) >> chan->backend.subbuf_size_order; | |
87 | } | |
88 | ||
89 | /* | |
90 | * Last TSC comparison functions. Check if the current TSC overflows tsc_bits | |
91 | * bits from the last TSC read. When overflows are detected, the full 64-bit | |
92 | * timestamp counter should be written in the record header. Reads and writes | |
93 | * last_tsc atomically. | |
94 | */ | |
95 | ||
96 | #if (BITS_PER_LONG == 32) | |
97 | static inline | |
98 | void save_last_tsc(const struct lib_ring_buffer_config *config, | |
99 | struct lib_ring_buffer *buf, u64 tsc) | |
100 | { | |
101 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
102 | return; | |
103 | ||
104 | /* | |
105 | * Ensure the compiler performs this update in a single instruction. | |
106 | */ | |
107 | v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits)); | |
108 | } | |
109 | ||
110 | static inline | |
111 | int last_tsc_overflow(const struct lib_ring_buffer_config *config, | |
112 | struct lib_ring_buffer *buf, u64 tsc) | |
113 | { | |
114 | unsigned long tsc_shifted; | |
115 | ||
116 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
117 | return 0; | |
118 | ||
119 | tsc_shifted = (unsigned long)(tsc >> config->tsc_bits); | |
120 | if (unlikely(tsc_shifted | |
121 | - (unsigned long)v_read(config, &buf->last_tsc))) | |
122 | return 1; | |
123 | else | |
124 | return 0; | |
125 | } | |
126 | #else | |
127 | static inline | |
128 | void save_last_tsc(const struct lib_ring_buffer_config *config, | |
129 | struct lib_ring_buffer *buf, u64 tsc) | |
130 | { | |
131 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
132 | return; | |
133 | ||
134 | v_set(config, &buf->last_tsc, (unsigned long)tsc); | |
135 | } | |
136 | ||
137 | static inline | |
138 | int last_tsc_overflow(const struct lib_ring_buffer_config *config, | |
139 | struct lib_ring_buffer *buf, u64 tsc) | |
140 | { | |
141 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
142 | return 0; | |
143 | ||
144 | if (unlikely((tsc - v_read(config, &buf->last_tsc)) | |
145 | >> config->tsc_bits)) | |
146 | return 1; | |
147 | else | |
148 | return 0; | |
149 | } | |
150 | #endif | |
151 | ||
152 | extern | |
153 | int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx); | |
154 | ||
155 | extern | |
156 | void lib_ring_buffer_switch_slow(struct lib_ring_buffer *buf, | |
157 | enum switch_mode mode); | |
158 | ||
aece661f MD |
159 | extern |
160 | void lib_ring_buffer_check_deliver_slow(const struct lib_ring_buffer_config *config, | |
161 | struct lib_ring_buffer *buf, | |
162 | struct channel *chan, | |
163 | unsigned long offset, | |
164 | unsigned long commit_count, | |
165 | unsigned long idx, | |
166 | u64 tsc); | |
167 | ||
5e391252 MD |
168 | extern |
169 | void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf); | |
e1cdd6e9 MD |
170 | extern |
171 | void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf); | |
5e391252 | 172 | |
f3bc08c5 MD |
173 | /* Buffer write helpers */ |
174 | ||
175 | static inline | |
176 | void lib_ring_buffer_reserve_push_reader(struct lib_ring_buffer *buf, | |
177 | struct channel *chan, | |
178 | unsigned long offset) | |
179 | { | |
180 | unsigned long consumed_old, consumed_new; | |
181 | ||
182 | do { | |
183 | consumed_old = atomic_long_read(&buf->consumed); | |
184 | /* | |
185 | * If buffer is in overwrite mode, push the reader consumed | |
186 | * count if the write position has reached it and we are not | |
187 | * at the first iteration (don't push the reader farther than | |
188 | * the writer). This operation can be done concurrently by many | |
189 | * writers in the same buffer, the writer being at the farthest | |
190 | * write position sub-buffer index in the buffer being the one | |
191 | * which will win this loop. | |
192 | */ | |
193 | if (unlikely(subbuf_trunc(offset, chan) | |
194 | - subbuf_trunc(consumed_old, chan) | |
195 | >= chan->backend.buf_size)) | |
196 | consumed_new = subbuf_align(consumed_old, chan); | |
197 | else | |
198 | return; | |
199 | } while (unlikely(atomic_long_cmpxchg(&buf->consumed, consumed_old, | |
200 | consumed_new) != consumed_old)); | |
201 | } | |
202 | ||
f3bc08c5 MD |
203 | static inline |
204 | int lib_ring_buffer_pending_data(const struct lib_ring_buffer_config *config, | |
205 | struct lib_ring_buffer *buf, | |
206 | struct channel *chan) | |
207 | { | |
208 | return !!subbuf_offset(v_read(config, &buf->offset), chan); | |
209 | } | |
210 | ||
211 | static inline | |
212 | unsigned long lib_ring_buffer_get_data_size(const struct lib_ring_buffer_config *config, | |
213 | struct lib_ring_buffer *buf, | |
214 | unsigned long idx) | |
215 | { | |
216 | return subbuffer_get_data_size(config, &buf->backend, idx); | |
217 | } | |
218 | ||
219 | /* | |
220 | * Check if all space reservation in a buffer have been committed. This helps | |
221 | * knowing if an execution context is nested (for per-cpu buffers only). | |
222 | * This is a very specific ftrace use-case, so we keep this as "internal" API. | |
223 | */ | |
224 | static inline | |
225 | int lib_ring_buffer_reserve_committed(const struct lib_ring_buffer_config *config, | |
226 | struct lib_ring_buffer *buf, | |
227 | struct channel *chan) | |
228 | { | |
229 | unsigned long offset, idx, commit_count; | |
230 | ||
231 | CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU); | |
232 | CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU); | |
233 | ||
234 | /* | |
235 | * Read offset and commit count in a loop so they are both read | |
236 | * atomically wrt interrupts. By deal with interrupt concurrency by | |
237 | * restarting both reads if the offset has been pushed. Note that given | |
238 | * we only have to deal with interrupt concurrency here, an interrupt | |
239 | * modifying the commit count will also modify "offset", so it is safe | |
240 | * to only check for offset modifications. | |
241 | */ | |
242 | do { | |
243 | offset = v_read(config, &buf->offset); | |
244 | idx = subbuf_index(offset, chan); | |
245 | commit_count = v_read(config, &buf->commit_hot[idx].cc); | |
246 | } while (offset != v_read(config, &buf->offset)); | |
247 | ||
248 | return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) | |
249 | - (commit_count & chan->commit_count_mask) == 0); | |
250 | } | |
251 | ||
635e457c MD |
252 | /* |
253 | * Receive end of subbuffer TSC as parameter. It has been read in the | |
254 | * space reservation loop of either reserve or switch, which ensures it | |
255 | * progresses monotonically with event records in the buffer. Therefore, | |
256 | * it ensures that the end timestamp of a subbuffer is <= begin | |
257 | * timestamp of the following subbuffers. | |
258 | */ | |
f3bc08c5 MD |
259 | static inline |
260 | void lib_ring_buffer_check_deliver(const struct lib_ring_buffer_config *config, | |
261 | struct lib_ring_buffer *buf, | |
262 | struct channel *chan, | |
263 | unsigned long offset, | |
264 | unsigned long commit_count, | |
635e457c MD |
265 | unsigned long idx, |
266 | u64 tsc) | |
f3bc08c5 MD |
267 | { |
268 | unsigned long old_commit_count = commit_count | |
269 | - chan->backend.subbuf_size; | |
f3bc08c5 MD |
270 | |
271 | /* Check if all commits have been done */ | |
272 | if (unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) | |
aece661f MD |
273 | - (old_commit_count & chan->commit_count_mask) == 0)) |
274 | lib_ring_buffer_check_deliver_slow(config, buf, chan, offset, | |
275 | commit_count, idx, tsc); | |
f3bc08c5 MD |
276 | } |
277 | ||
278 | /* | |
279 | * lib_ring_buffer_write_commit_counter | |
280 | * | |
281 | * For flight recording. must be called after commit. | |
282 | * This function increments the subbuffer's commit_seq counter each time the | |
283 | * commit count reaches back the reserve offset (modulo subbuffer size). It is | |
284 | * useful for crash dump. | |
285 | */ | |
286 | static inline | |
287 | void lib_ring_buffer_write_commit_counter(const struct lib_ring_buffer_config *config, | |
288 | struct lib_ring_buffer *buf, | |
289 | struct channel *chan, | |
f3bc08c5 | 290 | unsigned long buf_offset, |
8ec496cf MD |
291 | unsigned long commit_count, |
292 | struct commit_counters_hot *cc_hot) | |
f3bc08c5 | 293 | { |
7915e163 | 294 | unsigned long commit_seq_old; |
f3bc08c5 MD |
295 | |
296 | if (config->oops != RING_BUFFER_OOPS_CONSISTENCY) | |
297 | return; | |
298 | ||
f3bc08c5 MD |
299 | /* |
300 | * subbuf_offset includes commit_count_mask. We can simply | |
301 | * compare the offsets within the subbuffer without caring about | |
302 | * buffer full/empty mismatch because offset is never zero here | |
303 | * (subbuffer header and record headers have non-zero length). | |
304 | */ | |
7915e163 | 305 | if (unlikely(subbuf_offset(buf_offset - commit_count, chan))) |
f3bc08c5 MD |
306 | return; |
307 | ||
8ec496cf | 308 | commit_seq_old = v_read(config, &cc_hot->seq); |
6212b6b6 | 309 | if (likely((long) (commit_seq_old - commit_count) < 0)) |
8ec496cf | 310 | v_set(config, &cc_hot->seq, commit_count); |
f3bc08c5 MD |
311 | } |
312 | ||
313 | extern int lib_ring_buffer_create(struct lib_ring_buffer *buf, | |
314 | struct channel_backend *chanb, int cpu); | |
315 | extern void lib_ring_buffer_free(struct lib_ring_buffer *buf); | |
316 | ||
317 | /* Keep track of trap nesting inside ring buffer code */ | |
318 | DECLARE_PER_CPU(unsigned int, lib_ring_buffer_nesting); | |
319 | ||
886d51a3 | 320 | #endif /* _LIB_RING_BUFFER_FRONTEND_INTERNAL_H */ |