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>
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_lib_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_lib_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_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
,
84 uint64_t *memory_map_size
)
85 __attribute__((visibility("hidden")));
88 int 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")));
94 int 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")));
100 int 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
,
104 __attribute__((visibility("hidden")));
107 int 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
,
111 __attribute__((visibility("hidden")));
113 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer
*buf
,
114 struct lttng_ust_shm_handle
*handle
)
115 __attribute__((visibility("hidden")));
117 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer
*buf
,
118 struct lttng_ust_shm_handle
*handle
)
119 __attribute__((visibility("hidden")));
122 * Initialize signals for ring buffer. Should be called early e.g. by
123 * main() in the program to affect all threads.
125 void lib_ringbuffer_signal_init(void)
126 __attribute__((visibility("hidden")));
129 * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
131 extern 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")));
137 extern 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")));
144 extern 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")));
149 extern 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")));
154 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer
*buf
,
155 struct lttng_ust_shm_handle
*handle
)
156 __attribute__((visibility("hidden")));
159 * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
160 * to read sub-buffers sequentially.
162 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer
*buf
,
163 struct lttng_ust_shm_handle
*handle
)
167 ret
= lib_ring_buffer_snapshot(buf
, &buf
->cons_snapshot
,
168 &buf
->prod_snapshot
, handle
);
171 ret
= lib_ring_buffer_get_subbuf(buf
, buf
->cons_snapshot
, handle
);
176 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer
*buf
,
177 struct lttng_ust_shm_handle
*handle
)
179 struct lttng_ust_lib_ring_buffer_channel
*chan
;
181 chan
= shmp(handle
, buf
->backend
.chan
);
184 lib_ring_buffer_put_subbuf(buf
, handle
);
185 lib_ring_buffer_move_consumer(buf
, subbuf_align(buf
->cons_snapshot
, chan
),
189 extern void channel_reset(struct lttng_ust_lib_ring_buffer_channel
*chan
)
190 __attribute__((visibility("hidden")));
192 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer
*buf
,
193 struct lttng_ust_shm_handle
*handle
)
194 __attribute__((visibility("hidden")));
197 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config
*config
,
198 struct lttng_ust_lib_ring_buffer
*buf
)
200 return v_read(config
, &buf
->offset
);
204 unsigned long lib_ring_buffer_get_consumed(
205 const struct lttng_ust_lib_ring_buffer_config
*config
__attribute__((unused
)),
206 struct lttng_ust_lib_ring_buffer
*buf
)
208 return uatomic_read(&buf
->consumed
);
212 * Must call lib_ring_buffer_is_finalized before reading counters (memory
213 * ordering enforced with respect to trace teardown).
216 int lib_ring_buffer_is_finalized(
217 const struct lttng_ust_lib_ring_buffer_config
*config
__attribute__((unused
)),
218 struct lttng_ust_lib_ring_buffer
*buf
)
220 int finalized
= CMM_ACCESS_ONCE(buf
->finalized
);
222 * Read finalized before counters.
229 int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_lib_ring_buffer_channel
*chan
)
231 return chan
->finalized
;
235 int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_lib_ring_buffer_channel
*chan
)
237 return uatomic_read(&chan
->record_disabled
);
241 unsigned long lib_ring_buffer_get_read_data_size(
242 const struct lttng_ust_lib_ring_buffer_config
*config
,
243 struct lttng_ust_lib_ring_buffer
*buf
,
244 struct lttng_ust_shm_handle
*handle
)
246 return subbuffer_get_read_data_size(config
, &buf
->backend
, handle
);
250 unsigned long lib_ring_buffer_get_records_count(
251 const struct lttng_ust_lib_ring_buffer_config
*config
,
252 struct lttng_ust_lib_ring_buffer
*buf
)
254 return v_read(config
, &buf
->records_count
);
258 unsigned long lib_ring_buffer_get_records_overrun(
259 const struct lttng_ust_lib_ring_buffer_config
*config
,
260 struct lttng_ust_lib_ring_buffer
*buf
)
262 return v_read(config
, &buf
->records_overrun
);
266 unsigned long lib_ring_buffer_get_records_lost_full(
267 const struct lttng_ust_lib_ring_buffer_config
*config
,
268 struct lttng_ust_lib_ring_buffer
*buf
)
270 return v_read(config
, &buf
->records_lost_full
);
274 unsigned long lib_ring_buffer_get_records_lost_wrap(
275 const struct lttng_ust_lib_ring_buffer_config
*config
,
276 struct lttng_ust_lib_ring_buffer
*buf
)
278 return v_read(config
, &buf
->records_lost_wrap
);
282 unsigned long lib_ring_buffer_get_records_lost_big(
283 const struct lttng_ust_lib_ring_buffer_config
*config
,
284 struct lttng_ust_lib_ring_buffer
*buf
)
286 return v_read(config
, &buf
->records_lost_big
);
290 unsigned long lib_ring_buffer_get_records_read(
291 const struct lttng_ust_lib_ring_buffer_config
*config
,
292 struct lttng_ust_lib_ring_buffer
*buf
)
294 return v_read(config
, &buf
->backend
.records_read
);
297 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */