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.
42 __attribute__((visibility("hidden")))
44 struct lttng_ust_shm_handle
*channel_create(const struct lttng_ust_lib_ring_buffer_config
*config
,
46 size_t priv_data_align
,
47 size_t priv_data_size
,
51 size_t subbuf_size
, size_t num_subbuf
,
52 unsigned int switch_timer_interval
,
53 unsigned int read_timer_interval
,
54 const int *stream_fds
, int nr_stream_fds
,
55 int64_t blocking_timeout
);
58 * channel_destroy finalizes all channel's buffers, waits for readers to
59 * release all references, and destroys the channel.
61 __attribute__((visibility("hidden")))
63 void channel_destroy(struct lttng_ust_lib_ring_buffer_channel
*chan
,
64 struct lttng_ust_shm_handle
*handle
,
68 /* Buffer read operations */
71 * Iteration on channel cpumask needs to issue a read barrier to match the write
72 * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
73 * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
74 * only performed at channel destruction.
76 #define for_each_channel_cpu(cpu, chan) \
77 for_each_possible_cpu(cpu)
79 __attribute__((visibility("hidden")))
80 extern struct lttng_ust_lib_ring_buffer
*channel_get_ring_buffer(
81 const struct lttng_ust_lib_ring_buffer_config
*config
,
82 struct lttng_ust_lib_ring_buffer_channel
*chan
, int cpu
,
83 struct lttng_ust_shm_handle
*handle
,
84 int *shm_fd
, int *wait_fd
,
86 uint64_t *memory_map_size
);
88 __attribute__((visibility("hidden")))
90 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config
*config
,
91 struct lttng_ust_lib_ring_buffer_channel
*chan
,
92 struct lttng_ust_shm_handle
*handle
);
94 __attribute__((visibility("hidden")))
96 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config
*config
,
97 struct lttng_ust_lib_ring_buffer_channel
*chan
,
98 struct lttng_ust_shm_handle
*handle
);
100 __attribute__((visibility("hidden")))
102 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config
*config
,
103 struct lttng_ust_lib_ring_buffer_channel
*chan
,
104 struct lttng_ust_shm_handle
*handle
,
107 __attribute__((visibility("hidden")))
109 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config
*config
,
110 struct lttng_ust_lib_ring_buffer_channel
*chan
,
111 struct lttng_ust_shm_handle
*handle
,
114 __attribute__((visibility("hidden")))
115 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer
*buf
,
116 struct lttng_ust_shm_handle
*handle
);
118 __attribute__((visibility("hidden")))
119 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer
*buf
,
120 struct lttng_ust_shm_handle
*handle
);
123 * Initialize signals for ring buffer. Should be called early e.g. by
124 * main() in the program to affect all threads.
126 __attribute__((visibility("hidden")))
127 void lib_ringbuffer_signal_init(void);
130 * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
132 __attribute__((visibility("hidden")))
133 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer
*buf
,
134 unsigned long *consumed
,
135 unsigned long *produced
,
136 struct lttng_ust_shm_handle
*handle
);
138 __attribute__((visibility("hidden")))
139 extern int lib_ring_buffer_snapshot_sample_positions(
140 struct lttng_ust_lib_ring_buffer
*buf
,
141 unsigned long *consumed
,
142 unsigned long *produced
,
143 struct lttng_ust_shm_handle
*handle
);
145 __attribute__((visibility("hidden")))
146 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer
*buf
,
147 unsigned long consumed_new
,
148 struct lttng_ust_shm_handle
*handle
);
150 __attribute__((visibility("hidden")))
151 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer
*buf
,
152 unsigned long consumed
,
153 struct lttng_ust_shm_handle
*handle
);
154 __attribute__((visibility("hidden")))
155 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer
*buf
,
156 struct lttng_ust_shm_handle
*handle
);
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 __attribute__((visibility("hidden")))
190 extern void channel_reset(struct lttng_ust_lib_ring_buffer_channel
*chan
);
192 __attribute__((visibility("hidden")))
193 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer
*buf
,
194 struct lttng_ust_shm_handle
*handle
);
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(const struct lttng_ust_lib_ring_buffer_config
*config
,
205 struct lttng_ust_lib_ring_buffer
*buf
)
207 return uatomic_read(&buf
->consumed
);
211 * Must call lib_ring_buffer_is_finalized before reading counters (memory
212 * ordering enforced with respect to trace teardown).
215 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config
*config
,
216 struct lttng_ust_lib_ring_buffer
*buf
)
218 int finalized
= CMM_ACCESS_ONCE(buf
->finalized
);
220 * Read finalized before counters.
227 int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_lib_ring_buffer_channel
*chan
)
229 return chan
->finalized
;
233 int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_lib_ring_buffer_channel
*chan
)
235 return uatomic_read(&chan
->record_disabled
);
239 unsigned 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
)
244 return subbuffer_get_read_data_size(config
, &buf
->backend
, handle
);
248 unsigned 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
)
252 return v_read(config
, &buf
->records_count
);
256 unsigned 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
)
260 return v_read(config
, &buf
->records_overrun
);
264 unsigned 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
)
268 return v_read(config
, &buf
->records_lost_full
);
272 unsigned 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
)
276 return v_read(config
, &buf
->records_lost_wrap
);
280 unsigned 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
)
284 return v_read(config
, &buf
->records_lost_big
);
288 unsigned 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
)
292 return v_read(config
, &buf
->backend
.records_read
);
295 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */