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[lttng-ust.git] / libringbuffer / frontend.h
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1/*
2 * SPDX-License-Identifier: LGPL-2.1-only
3 *
4 * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 *
6 * Ring Buffer Library Synchronization Header (API).
7 *
8 * See ring_buffer_frontend.c for more information on wait-free algorithms.
9 */
10
11#ifndef _LTTNG_RING_BUFFER_FRONTEND_H
12#define _LTTNG_RING_BUFFER_FRONTEND_H
13
14#include <stddef.h>
15#include <stdint.h>
16
17#include <urcu/compiler.h>
18#include <urcu/uatomic.h>
19
20#include "smp.h"
21
22/* Internal helpers */
23#include "frontend_internal.h"
24
25/* Buffer creation/removal and setup operations */
26
27/*
28 * switch_timer_interval is the time interval (in us) to fill sub-buffers with
29 * padding to let readers get those sub-buffers. Used for live streaming.
30 *
31 * read_timer_interval is the time interval (in us) to wake up pending readers.
32 *
33 * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
34 * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
35 * be set to NULL for other backends.
36 *
37 * private data is a memory area for configuration data. This memory is
38 * managed by lib ring buffer. priv_data_align is the alignment required
39 * for the private data area.
40 */
41
42extern
43struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
44 const char *name,
45 size_t priv_data_align,
46 size_t priv_data_size,
47 void *priv_data_init,
48 void *priv,
49 void *buf_addr,
50 size_t subbuf_size, size_t num_subbuf,
51 unsigned int switch_timer_interval,
52 unsigned int read_timer_interval,
53 const int *stream_fds, int nr_stream_fds,
54 int64_t blocking_timeout)
55 __attribute__((visibility("hidden")));
56
57/*
58 * channel_destroy finalizes all channel's buffers, waits for readers to
59 * release all references, and destroys the channel.
60 */
61void channel_destroy(struct lttng_ust_lib_ring_buffer_channel *chan,
62 struct lttng_ust_shm_handle *handle,
63 int consumer)
64 __attribute__((visibility("hidden")));
65
66
67/* Buffer read operations */
68
69/*
70 * Iteration on channel cpumask needs to issue a read barrier to match the write
71 * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
72 * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
73 * only performed at channel destruction.
74 */
75#define for_each_channel_cpu(cpu, chan) \
76 for_each_possible_cpu(cpu)
77
78extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
79 const struct lttng_ust_lib_ring_buffer_config *config,
80 struct lttng_ust_lib_ring_buffer_channel *chan, int cpu,
81 struct lttng_ust_shm_handle *handle,
82 int *shm_fd, int *wait_fd,
83 int *wakeup_fd,
84 uint64_t *memory_map_size)
85 __attribute__((visibility("hidden")));
86
87extern
88int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
89 struct lttng_ust_lib_ring_buffer_channel *chan,
90 struct lttng_ust_shm_handle *handle)
91 __attribute__((visibility("hidden")));
92
93extern
94int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
95 struct lttng_ust_lib_ring_buffer_channel *chan,
96 struct lttng_ust_shm_handle *handle)
97 __attribute__((visibility("hidden")));
98
99extern
100int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
101 struct lttng_ust_lib_ring_buffer_channel *chan,
102 struct lttng_ust_shm_handle *handle,
103 int cpu)
104 __attribute__((visibility("hidden")));
105
106extern
107int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
108 struct lttng_ust_lib_ring_buffer_channel *chan,
109 struct lttng_ust_shm_handle *handle,
110 int cpu)
111 __attribute__((visibility("hidden")));
112
113extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
114 struct lttng_ust_shm_handle *handle)
115 __attribute__((visibility("hidden")));
116
117extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
118 struct lttng_ust_shm_handle *handle)
119 __attribute__((visibility("hidden")));
120
121/*
122 * Initialize signals for ring buffer. Should be called early e.g. by
123 * main() in the program to affect all threads.
124 */
125void lib_ringbuffer_signal_init(void)
126 __attribute__((visibility("hidden")));
127
128/*
129 * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
130 */
131extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
132 unsigned long *consumed,
133 unsigned long *produced,
134 struct lttng_ust_shm_handle *handle)
135 __attribute__((visibility("hidden")));
136
137extern int lib_ring_buffer_snapshot_sample_positions(
138 struct lttng_ust_lib_ring_buffer *buf,
139 unsigned long *consumed,
140 unsigned long *produced,
141 struct lttng_ust_shm_handle *handle)
142 __attribute__((visibility("hidden")));
143
144extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
145 unsigned long consumed_new,
146 struct lttng_ust_shm_handle *handle)
147 __attribute__((visibility("hidden")));
148
149extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
150 unsigned long consumed,
151 struct lttng_ust_shm_handle *handle)
152 __attribute__((visibility("hidden")));
153
154extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
155 struct lttng_ust_shm_handle *handle)
156 __attribute__((visibility("hidden")));
157
158/*
159 * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
160 * to read sub-buffers sequentially.
161 */
162static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
163 struct lttng_ust_shm_handle *handle)
164{
165 int ret;
166
167 ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
168 &buf->prod_snapshot, handle);
169 if (ret)
170 return ret;
171 ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
172 return ret;
173}
174
175static inline
176void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
177 struct lttng_ust_shm_handle *handle)
178{
179 struct lttng_ust_lib_ring_buffer_channel *chan;
180
181 chan = shmp(handle, buf->backend.chan);
182 if (!chan)
183 return;
184 lib_ring_buffer_put_subbuf(buf, handle);
185 lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
186 handle);
187}
188
189extern void channel_reset(struct lttng_ust_lib_ring_buffer_channel *chan)
190 __attribute__((visibility("hidden")));
191
192extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
193 struct lttng_ust_shm_handle *handle)
194 __attribute__((visibility("hidden")));
195
196static inline
197unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
198 struct lttng_ust_lib_ring_buffer *buf)
199{
200 return v_read(config, &buf->offset);
201}
202
203static inline
204unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
205 struct lttng_ust_lib_ring_buffer *buf)
206{
207 return uatomic_read(&buf->consumed);
208}
209
210/*
211 * Must call lib_ring_buffer_is_finalized before reading counters (memory
212 * ordering enforced with respect to trace teardown).
213 */
214static inline
215int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
216 struct lttng_ust_lib_ring_buffer *buf)
217{
218 int finalized = CMM_ACCESS_ONCE(buf->finalized);
219 /*
220 * Read finalized before counters.
221 */
222 cmm_smp_rmb();
223 return finalized;
224}
225
226static inline
227int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_lib_ring_buffer_channel *chan)
228{
229 return chan->finalized;
230}
231
232static inline
233int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_lib_ring_buffer_channel *chan)
234{
235 return uatomic_read(&chan->record_disabled);
236}
237
238static inline
239unsigned long lib_ring_buffer_get_read_data_size(
240 const struct lttng_ust_lib_ring_buffer_config *config,
241 struct lttng_ust_lib_ring_buffer *buf,
242 struct lttng_ust_shm_handle *handle)
243{
244 return subbuffer_get_read_data_size(config, &buf->backend, handle);
245}
246
247static inline
248unsigned long lib_ring_buffer_get_records_count(
249 const struct lttng_ust_lib_ring_buffer_config *config,
250 struct lttng_ust_lib_ring_buffer *buf)
251{
252 return v_read(config, &buf->records_count);
253}
254
255static inline
256unsigned long lib_ring_buffer_get_records_overrun(
257 const struct lttng_ust_lib_ring_buffer_config *config,
258 struct lttng_ust_lib_ring_buffer *buf)
259{
260 return v_read(config, &buf->records_overrun);
261}
262
263static inline
264unsigned long lib_ring_buffer_get_records_lost_full(
265 const struct lttng_ust_lib_ring_buffer_config *config,
266 struct lttng_ust_lib_ring_buffer *buf)
267{
268 return v_read(config, &buf->records_lost_full);
269}
270
271static inline
272unsigned long lib_ring_buffer_get_records_lost_wrap(
273 const struct lttng_ust_lib_ring_buffer_config *config,
274 struct lttng_ust_lib_ring_buffer *buf)
275{
276 return v_read(config, &buf->records_lost_wrap);
277}
278
279static inline
280unsigned long lib_ring_buffer_get_records_lost_big(
281 const struct lttng_ust_lib_ring_buffer_config *config,
282 struct lttng_ust_lib_ring_buffer *buf)
283{
284 return v_read(config, &buf->records_lost_big);
285}
286
287static inline
288unsigned long lib_ring_buffer_get_records_read(
289 const struct lttng_ust_lib_ring_buffer_config *config,
290 struct lttng_ust_lib_ring_buffer *buf)
291{
292 return v_read(config, &buf->backend.records_read);
293}
294
295#endif /* _LTTNG_RING_BUFFER_FRONTEND_H */
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