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e92f3e28 MD |
1 | #ifndef _LTTNG_RING_BUFFER_BACKEND_H |
2 | #define _LTTNG_RING_BUFFER_BACKEND_H | |
852c2936 MD |
3 | |
4 | /* | |
e92f3e28 | 5 | * libringbuffer/backend.h |
852c2936 MD |
6 | * |
7 | * Ring buffer backend (API). | |
8 | * | |
e92f3e28 MD |
9 | * Copyright (C) 2011-2012 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 | |
852c2936 MD |
24 | * |
25 | * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by | |
26 | * the reader in flight recorder mode. | |
27 | */ | |
28 | ||
14641deb MD |
29 | #include <unistd.h> |
30 | ||
852c2936 | 31 | /* Internal helpers */ |
4931a13e MD |
32 | #include "backend_internal.h" |
33 | #include "frontend_internal.h" | |
852c2936 MD |
34 | |
35 | /* Ring buffer backend API */ | |
36 | ||
37 | /* Ring buffer backend access (read/write) */ | |
38 | ||
4cfec15c | 39 | extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 40 | size_t offset, void *dest, size_t len, |
38fae1d3 | 41 | struct lttng_ust_shm_handle *handle); |
852c2936 | 42 | |
4cfec15c | 43 | extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 44 | size_t offset, void *dest, size_t len, |
38fae1d3 | 45 | struct lttng_ust_shm_handle *handle); |
852c2936 | 46 | |
852c2936 MD |
47 | /* |
48 | * Return the address where a given offset is located. | |
49 | * Should be used to get the current subbuffer header pointer. Given we know | |
50 | * it's never on a page boundary, it's safe to write directly to this address, | |
51 | * as long as the write is never bigger than a page size. | |
52 | */ | |
53 | extern void * | |
4cfec15c | 54 | lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 55 | size_t offset, |
38fae1d3 | 56 | struct lttng_ust_shm_handle *handle); |
852c2936 | 57 | extern void * |
4cfec15c | 58 | lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 59 | size_t offset, |
38fae1d3 | 60 | struct lttng_ust_shm_handle *handle); |
852c2936 MD |
61 | |
62 | /** | |
63 | * lib_ring_buffer_write - write data to a buffer backend | |
64 | * @config : ring buffer instance configuration | |
65 | * @ctx: ring buffer context. (input arguments only) | |
66 | * @src : source pointer to copy from | |
67 | * @len : length of data to copy | |
68 | * | |
69 | * This function copies "len" bytes of data from a source pointer to a buffer | |
70 | * backend, at the current context offset. This is more or less a buffer | |
71 | * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write) | |
72 | * if copy is crossing a page boundary. | |
73 | */ | |
74 | static inline | |
4cfec15c MD |
75 | void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config, |
76 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
852c2936 MD |
77 | const void *src, size_t len) |
78 | { | |
4cfec15c | 79 | struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend; |
852c2936 | 80 | struct channel_backend *chanb = &ctx->chan->backend; |
38fae1d3 | 81 | struct lttng_ust_shm_handle *handle = ctx->handle; |
a6352fd4 | 82 | size_t sbidx; |
852c2936 | 83 | size_t offset = ctx->buf_offset; |
4cfec15c | 84 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
852c2936 MD |
85 | unsigned long sb_bindex, id; |
86 | ||
0bf3c920 MD |
87 | if (caa_unlikely(!len)) |
88 | return; | |
852c2936 MD |
89 | offset &= chanb->buf_size - 1; |
90 | sbidx = offset >> chanb->subbuf_size_order; | |
4746ae29 | 91 | id = shmp_index(handle, bufb->buf_wsb, sbidx)->id; |
852c2936 | 92 | sb_bindex = subbuffer_id_get_index(config, id); |
4746ae29 | 93 | rpages = shmp_index(handle, bufb->array, sb_bindex); |
852c2936 MD |
94 | CHAN_WARN_ON(ctx->chan, |
95 | config->mode == RING_BUFFER_OVERWRITE | |
96 | && subbuffer_id_is_noref(config, id)); | |
a6352fd4 MD |
97 | /* |
98 | * Underlying layer should never ask for writes across | |
99 | * subbuffers. | |
100 | */ | |
101 | CHAN_WARN_ON(chanb, offset >= chanb->buf_size); | |
102 | lib_ring_buffer_do_copy(config, | |
aead2025 | 103 | shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1)), |
a6352fd4 | 104 | src, len); |
852c2936 MD |
105 | ctx->buf_offset += len; |
106 | } | |
107 | ||
108 | /* | |
109 | * This accessor counts the number of unread records in a buffer. | |
110 | * It only provides a consistent value if no reads not writes are performed | |
111 | * concurrently. | |
112 | */ | |
113 | static inline | |
114 | unsigned long lib_ring_buffer_get_records_unread( | |
4cfec15c MD |
115 | const struct lttng_ust_lib_ring_buffer_config *config, |
116 | struct lttng_ust_lib_ring_buffer *buf, | |
38fae1d3 | 117 | struct lttng_ust_shm_handle *handle) |
852c2936 | 118 | { |
4cfec15c MD |
119 | struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend; |
120 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages; | |
852c2936 MD |
121 | unsigned long records_unread = 0, sb_bindex, id; |
122 | unsigned int i; | |
123 | ||
1d498196 | 124 | for (i = 0; i < shmp(handle, bufb->chan)->backend.num_subbuf; i++) { |
4746ae29 | 125 | id = shmp_index(handle, bufb->buf_wsb, i)->id; |
852c2936 | 126 | sb_bindex = subbuffer_id_get_index(config, id); |
4746ae29 | 127 | pages = shmp_index(handle, bufb->array, sb_bindex); |
1d498196 | 128 | records_unread += v_read(config, &shmp(handle, pages->shmp)->records_unread); |
852c2936 MD |
129 | } |
130 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
131 | id = bufb->buf_rsb.id; | |
132 | sb_bindex = subbuffer_id_get_index(config, id); | |
4746ae29 | 133 | pages = shmp_index(handle, bufb->array, sb_bindex); |
1d498196 | 134 | records_unread += v_read(config, &shmp(handle, pages->shmp)->records_unread); |
852c2936 MD |
135 | } |
136 | return records_unread; | |
137 | } | |
138 | ||
e92f3e28 | 139 | #endif /* _LTTNG_RING_BUFFER_BACKEND_H */ |