2 * SPDX-License-Identifier: LGPL-2.1-only
4 * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 * Ring Buffer Library Synchronization Header (API).
8 * See ring_buffer_frontend.c for more information on wait-free algorithms.
11 #ifndef _LTTNG_RING_BUFFER_FRONTEND_H
12 #define _LTTNG_RING_BUFFER_FRONTEND_H
17 #include <urcu/compiler.h>
18 #include <urcu/uatomic.h>
20 #include "common/smp.h"
22 /* Internal helpers */
23 #include "frontend_internal.h"
25 /* Buffer creation/removal and setup operations */
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.
31 * read_timer_interval is the time interval (in us) to wake up pending readers.
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.
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.
43 struct lttng_ust_shm_handle
*channel_create(const struct lttng_ust_ring_buffer_config
*config
,
45 size_t priv_data_align
,
46 size_t priv_data_size
,
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")));
58 * channel_destroy finalizes all channel's buffers, waits for readers to
59 * release all references, and destroys the channel.
61 void channel_destroy(struct lttng_ust_ring_buffer_channel
*chan
,
62 struct lttng_ust_shm_handle
*handle
,
64 __attribute__((visibility("hidden")));
67 /* Buffer read operations */
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.
75 #define for_each_channel_cpu(cpu, chan) \
76 for_each_possible_cpu(cpu)
78 extern struct lttng_ust_ring_buffer
*channel_get_ring_buffer(
79 const struct lttng_ust_ring_buffer_config
*config
,
80 struct lttng_ust_ring_buffer_channel
*chan
, int cpu
,
81 struct lttng_ust_shm_handle
*handle
,
82 int *shm_fd
, int *wait_fd
,
84 uint64_t *memory_map_size
,
85 void **memory_map_addr
)
86 __attribute__((visibility("hidden")));
89 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_ring_buffer_config
*config
,
90 struct lttng_ust_ring_buffer_channel
*chan
,
91 struct lttng_ust_shm_handle
*handle
)
92 __attribute__((visibility("hidden")));
95 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_ring_buffer_config
*config
,
96 struct lttng_ust_ring_buffer_channel
*chan
,
97 struct lttng_ust_shm_handle
*handle
)
98 __attribute__((visibility("hidden")));
101 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_ring_buffer_config
*config
,
102 struct lttng_ust_ring_buffer_channel
*chan
,
103 struct lttng_ust_shm_handle
*handle
,
105 __attribute__((visibility("hidden")));
108 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_ring_buffer_config
*config
,
109 struct lttng_ust_ring_buffer_channel
*chan
,
110 struct lttng_ust_shm_handle
*handle
,
112 __attribute__((visibility("hidden")));
114 extern int lib_ring_buffer_open_read(struct lttng_ust_ring_buffer
*buf
,
115 struct lttng_ust_shm_handle
*handle
)
116 __attribute__((visibility("hidden")));
118 extern void lib_ring_buffer_release_read(struct lttng_ust_ring_buffer
*buf
,
119 struct lttng_ust_shm_handle
*handle
)
120 __attribute__((visibility("hidden")));
123 * Initialize signals for ring buffer. Should be called early e.g. by
124 * main() in the program to affect all threads.
126 void lib_ringbuffer_signal_init(void)
127 __attribute__((visibility("hidden")));
130 * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
132 extern int lib_ring_buffer_snapshot(struct lttng_ust_ring_buffer
*buf
,
133 unsigned long *consumed
,
134 unsigned long *produced
,
135 struct lttng_ust_shm_handle
*handle
)
136 __attribute__((visibility("hidden")));
138 extern int lib_ring_buffer_snapshot_sample_positions(
139 struct lttng_ust_ring_buffer
*buf
,
140 unsigned long *consumed
,
141 unsigned long *produced
,
142 struct lttng_ust_shm_handle
*handle
)
143 __attribute__((visibility("hidden")));
145 extern void lib_ring_buffer_move_consumer(struct lttng_ust_ring_buffer
*buf
,
146 unsigned long consumed_new
,
147 struct lttng_ust_shm_handle
*handle
)
148 __attribute__((visibility("hidden")));
150 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_ring_buffer
*buf
,
151 unsigned long consumed
,
152 struct lttng_ust_shm_handle
*handle
)
153 __attribute__((visibility("hidden")));
155 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_ring_buffer
*buf
,
156 struct lttng_ust_shm_handle
*handle
)
157 __attribute__((visibility("hidden")));
160 * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
161 * to read sub-buffers sequentially.
163 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_ring_buffer
*buf
,
164 struct lttng_ust_shm_handle
*handle
)
168 ret
= lib_ring_buffer_snapshot(buf
, &buf
->cons_snapshot
,
169 &buf
->prod_snapshot
, handle
);
172 ret
= lib_ring_buffer_get_subbuf(buf
, buf
->cons_snapshot
, handle
);
177 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_ring_buffer
*buf
,
178 struct lttng_ust_shm_handle
*handle
)
180 struct lttng_ust_ring_buffer_channel
*chan
;
182 chan
= shmp(handle
, buf
->backend
.chan
);
185 lib_ring_buffer_put_subbuf(buf
, handle
);
186 lib_ring_buffer_move_consumer(buf
, subbuf_align(buf
->cons_snapshot
, chan
),
190 extern void channel_reset(struct lttng_ust_ring_buffer_channel
*chan
)
191 __attribute__((visibility("hidden")));
193 extern void lib_ring_buffer_reset(struct lttng_ust_ring_buffer
*buf
,
194 struct lttng_ust_shm_handle
*handle
)
195 __attribute__((visibility("hidden")));
198 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_ring_buffer_config
*config
,
199 struct lttng_ust_ring_buffer
*buf
)
201 return v_read(config
, &buf
->offset
);
205 unsigned long lib_ring_buffer_get_consumed(
206 const struct lttng_ust_ring_buffer_config
*config
__attribute__((unused
)),
207 struct lttng_ust_ring_buffer
*buf
)
209 return uatomic_read(&buf
->consumed
);
213 * Must call lib_ring_buffer_is_finalized before reading counters (memory
214 * ordering enforced with respect to trace teardown).
217 int lib_ring_buffer_is_finalized(
218 const struct lttng_ust_ring_buffer_config
*config
__attribute__((unused
)),
219 struct lttng_ust_ring_buffer
*buf
)
221 int finalized
= CMM_ACCESS_ONCE(buf
->finalized
);
223 * Read finalized before counters.
230 int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_ring_buffer_channel
*chan
)
232 return chan
->finalized
;
236 int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_ring_buffer_channel
*chan
)
238 return uatomic_read(&chan
->record_disabled
);
242 unsigned long lib_ring_buffer_get_read_data_size(
243 const struct lttng_ust_ring_buffer_config
*config
,
244 struct lttng_ust_ring_buffer
*buf
,
245 struct lttng_ust_shm_handle
*handle
)
247 return subbuffer_get_read_data_size(config
, &buf
->backend
, handle
);
251 unsigned long lib_ring_buffer_get_records_count(
252 const struct lttng_ust_ring_buffer_config
*config
,
253 struct lttng_ust_ring_buffer
*buf
)
255 return v_read(config
, &buf
->records_count
);
259 unsigned long lib_ring_buffer_get_records_overrun(
260 const struct lttng_ust_ring_buffer_config
*config
,
261 struct lttng_ust_ring_buffer
*buf
)
263 return v_read(config
, &buf
->records_overrun
);
267 unsigned long lib_ring_buffer_get_records_lost_full(
268 const struct lttng_ust_ring_buffer_config
*config
__attribute__((unused
)),
269 const struct lttng_ust_ring_buffer_ctx
*ctx
)
271 return ctx
->priv
->records_lost_full
;
275 unsigned long lib_ring_buffer_get_records_lost_wrap(
276 const struct lttng_ust_ring_buffer_config
*config
__attribute__((unused
)),
277 const struct lttng_ust_ring_buffer_ctx
*ctx
)
279 return ctx
->priv
->records_lost_wrap
;
283 unsigned long lib_ring_buffer_get_records_lost_big(
284 const struct lttng_ust_ring_buffer_config
*config
__attribute__((unused
)),
285 const struct lttng_ust_ring_buffer_ctx
*ctx
)
287 return ctx
->priv
->records_lost_big
;
291 unsigned long lib_ring_buffer_get_records_read(
292 const struct lttng_ust_ring_buffer_config
*config
,
293 struct lttng_ust_ring_buffer
*buf
)
295 return v_read(config
, &buf
->backend
.records_read
);
298 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */