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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 | 85 | unsigned long sb_bindex, id; |
15500a1b MD |
86 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
87 | void *p; | |
852c2936 | 88 | |
0bf3c920 MD |
89 | if (caa_unlikely(!len)) |
90 | return; | |
852c2936 MD |
91 | offset &= chanb->buf_size - 1; |
92 | sbidx = offset >> chanb->subbuf_size_order; | |
4746ae29 | 93 | id = shmp_index(handle, bufb->buf_wsb, sbidx)->id; |
852c2936 | 94 | sb_bindex = subbuffer_id_get_index(config, id); |
4746ae29 | 95 | rpages = shmp_index(handle, bufb->array, sb_bindex); |
15500a1b MD |
96 | if (caa_unlikely(!rpages)) |
97 | return; | |
852c2936 MD |
98 | CHAN_WARN_ON(ctx->chan, |
99 | config->mode == RING_BUFFER_OVERWRITE | |
100 | && subbuffer_id_is_noref(config, id)); | |
a6352fd4 MD |
101 | /* |
102 | * Underlying layer should never ask for writes across | |
103 | * subbuffers. | |
104 | */ | |
105 | CHAN_WARN_ON(chanb, offset >= chanb->buf_size); | |
15500a1b MD |
106 | backend_pages = shmp(handle, rpages->shmp); |
107 | if (caa_unlikely(!backend_pages)) | |
108 | return; | |
109 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); | |
110 | if (caa_unlikely(!p)) | |
111 | return; | |
112 | lib_ring_buffer_do_copy(config, p, src, len); | |
852c2936 MD |
113 | ctx->buf_offset += len; |
114 | } | |
115 | ||
a44c74d9 MD |
116 | /* |
117 | * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL | |
118 | * terminating character is found in @src. Returns the number of bytes | |
119 | * copied. Does *not* terminate @dest with NULL terminating character. | |
120 | */ | |
121 | static inline | |
122 | size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, | |
123 | char *dest, const char *src, size_t len) | |
124 | { | |
125 | size_t count; | |
126 | ||
127 | for (count = 0; count < len; count++) { | |
128 | char c; | |
129 | ||
130 | /* | |
131 | * Only read source character once, in case it is | |
132 | * modified concurrently. | |
133 | */ | |
134 | c = CMM_LOAD_SHARED(src[count]); | |
135 | if (!c) | |
136 | break; | |
137 | lib_ring_buffer_do_copy(config, &dest[count], &c, 1); | |
138 | } | |
139 | return count; | |
140 | } | |
141 | ||
142 | /** | |
143 | * lib_ring_buffer_strcpy - write string data to a buffer backend | |
144 | * @config : ring buffer instance configuration | |
145 | * @ctx: ring buffer context. (input arguments only) | |
146 | * @src : source pointer to copy from | |
147 | * @len : length of data to copy | |
148 | * @pad : character to use for padding | |
149 | * | |
150 | * This function copies @len - 1 bytes of string data from a source | |
151 | * pointer to a buffer backend, followed by a terminating '\0' | |
152 | * character, at the current context offset. This is more or less a | |
153 | * buffer backend-specific strncpy() operation. If a terminating '\0' | |
154 | * character is found in @src before @len - 1 characters are copied, pad | |
155 | * the buffer with @pad characters (e.g. '#'). | |
156 | */ | |
157 | static inline | |
158 | void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, | |
159 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
160 | const char *src, size_t len, int pad) | |
161 | { | |
162 | struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend; | |
163 | struct channel_backend *chanb = &ctx->chan->backend; | |
164 | struct lttng_ust_shm_handle *handle = ctx->handle; | |
165 | size_t sbidx, count; | |
166 | size_t offset = ctx->buf_offset; | |
167 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
168 | unsigned long sb_bindex, id; | |
169 | ||
170 | if (caa_unlikely(!len)) | |
171 | return; | |
172 | offset &= chanb->buf_size - 1; | |
173 | sbidx = offset >> chanb->subbuf_size_order; | |
174 | id = shmp_index(handle, bufb->buf_wsb, sbidx)->id; | |
175 | sb_bindex = subbuffer_id_get_index(config, id); | |
176 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
177 | CHAN_WARN_ON(ctx->chan, | |
178 | config->mode == RING_BUFFER_OVERWRITE | |
179 | && subbuffer_id_is_noref(config, id)); | |
180 | /* | |
181 | * Underlying layer should never ask for writes across | |
182 | * subbuffers. | |
183 | */ | |
184 | CHAN_WARN_ON(chanb, offset >= chanb->buf_size); | |
185 | count = lib_ring_buffer_do_strcpy(config, | |
186 | shmp_index(handle, shmp(handle, rpages->shmp)->p, | |
187 | offset & (chanb->subbuf_size - 1)), | |
188 | src, len - 1); | |
189 | offset += count; | |
190 | /* Padding */ | |
191 | if (caa_unlikely(count < len - 1)) { | |
192 | size_t pad_len = len - 1 - count; | |
193 | ||
194 | lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p, | |
195 | offset & (chanb->subbuf_size - 1)), | |
196 | pad, pad_len); | |
197 | offset += pad_len; | |
198 | } | |
199 | /* Final '\0' */ | |
200 | lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p, | |
201 | offset & (chanb->subbuf_size - 1)), | |
202 | '\0', 1); | |
203 | ctx->buf_offset += len; | |
204 | } | |
205 | ||
852c2936 MD |
206 | /* |
207 | * This accessor counts the number of unread records in a buffer. | |
208 | * It only provides a consistent value if no reads not writes are performed | |
209 | * concurrently. | |
210 | */ | |
211 | static inline | |
212 | unsigned long lib_ring_buffer_get_records_unread( | |
4cfec15c MD |
213 | const struct lttng_ust_lib_ring_buffer_config *config, |
214 | struct lttng_ust_lib_ring_buffer *buf, | |
38fae1d3 | 215 | struct lttng_ust_shm_handle *handle) |
852c2936 | 216 | { |
4cfec15c | 217 | struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend; |
15500a1b | 218 | unsigned long records_unread = 0, sb_bindex; |
852c2936 | 219 | unsigned int i; |
15500a1b | 220 | struct channel *chan; |
852c2936 | 221 | |
15500a1b MD |
222 | chan = shmp(handle, bufb->chan); |
223 | if (!chan) | |
224 | return 0; | |
225 | for (i = 0; i < chan->backend.num_subbuf; i++) { | |
226 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; | |
227 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
228 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
229 | ||
230 | wsb = shmp_index(handle, bufb->buf_wsb, i); | |
231 | if (!wsb) | |
232 | return 0; | |
233 | sb_bindex = subbuffer_id_get_index(config, wsb->id); | |
234 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
235 | if (!rpages) | |
236 | return 0; | |
237 | backend_pages = shmp(handle, rpages->shmp); | |
238 | if (!backend_pages) | |
239 | return 0; | |
240 | records_unread += v_read(config, &backend_pages->records_unread); | |
852c2936 MD |
241 | } |
242 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
15500a1b MD |
243 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
244 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
245 | ||
246 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
247 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
248 | if (!rpages) | |
249 | return 0; | |
250 | backend_pages = shmp(handle, rpages->shmp); | |
251 | if (!backend_pages) | |
252 | return 0; | |
253 | records_unread += v_read(config, &backend_pages->records_unread); | |
852c2936 MD |
254 | } |
255 | return records_unread; | |
256 | } | |
257 | ||
e92f3e28 | 258 | #endif /* _LTTNG_RING_BUFFER_BACKEND_H */ |