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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 | ||
b4051ad8 | 29 | #include <stddef.h> |
14641deb MD |
30 | #include <unistd.h> |
31 | ||
852c2936 | 32 | /* Internal helpers */ |
4931a13e MD |
33 | #include "backend_internal.h" |
34 | #include "frontend_internal.h" | |
852c2936 MD |
35 | |
36 | /* Ring buffer backend API */ | |
37 | ||
38 | /* Ring buffer backend access (read/write) */ | |
39 | ||
4cfec15c | 40 | extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 41 | size_t offset, void *dest, size_t len, |
38fae1d3 | 42 | struct lttng_ust_shm_handle *handle); |
852c2936 | 43 | |
4cfec15c | 44 | extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 45 | size_t offset, void *dest, size_t len, |
38fae1d3 | 46 | struct lttng_ust_shm_handle *handle); |
852c2936 | 47 | |
852c2936 MD |
48 | /* |
49 | * Return the address where a given offset is located. | |
50 | * Should be used to get the current subbuffer header pointer. Given we know | |
51 | * it's never on a page boundary, it's safe to write directly to this address, | |
52 | * as long as the write is never bigger than a page size. | |
53 | */ | |
54 | extern void * | |
4cfec15c | 55 | lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 56 | size_t offset, |
38fae1d3 | 57 | struct lttng_ust_shm_handle *handle); |
852c2936 | 58 | extern void * |
4cfec15c | 59 | lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 60 | size_t offset, |
38fae1d3 | 61 | struct lttng_ust_shm_handle *handle); |
852c2936 MD |
62 | |
63 | /** | |
64 | * lib_ring_buffer_write - write data to a buffer backend | |
65 | * @config : ring buffer instance configuration | |
66 | * @ctx: ring buffer context. (input arguments only) | |
67 | * @src : source pointer to copy from | |
68 | * @len : length of data to copy | |
69 | * | |
70 | * This function copies "len" bytes of data from a source pointer to a buffer | |
71 | * backend, at the current context offset. This is more or less a buffer | |
72 | * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write) | |
73 | * if copy is crossing a page boundary. | |
74 | */ | |
00d0f8eb | 75 | static inline __attribute__((always_inline)) |
4cfec15c MD |
76 | void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config, |
77 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
852c2936 MD |
78 | const void *src, size_t len) |
79 | { | |
852c2936 | 80 | struct channel_backend *chanb = &ctx->chan->backend; |
38fae1d3 | 81 | struct lttng_ust_shm_handle *handle = ctx->handle; |
852c2936 | 82 | size_t offset = ctx->buf_offset; |
15500a1b MD |
83 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
84 | void *p; | |
852c2936 | 85 | |
0bf3c920 MD |
86 | if (caa_unlikely(!len)) |
87 | return; | |
a6352fd4 MD |
88 | /* |
89 | * Underlying layer should never ask for writes across | |
90 | * subbuffers. | |
91 | */ | |
a3492932 MD |
92 | CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size); |
93 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); | |
94 | if (caa_unlikely(!backend_pages)) { | |
95 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
96 | return; | |
97 | } | |
15500a1b MD |
98 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
99 | if (caa_unlikely(!p)) | |
100 | return; | |
101 | lib_ring_buffer_do_copy(config, p, src, len); | |
852c2936 MD |
102 | ctx->buf_offset += len; |
103 | } | |
104 | ||
a44c74d9 MD |
105 | /* |
106 | * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL | |
107 | * terminating character is found in @src. Returns the number of bytes | |
108 | * copied. Does *not* terminate @dest with NULL terminating character. | |
109 | */ | |
00d0f8eb | 110 | static inline __attribute__((always_inline)) |
a44c74d9 MD |
111 | size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, |
112 | char *dest, const char *src, size_t len) | |
113 | { | |
114 | size_t count; | |
115 | ||
116 | for (count = 0; count < len; count++) { | |
117 | char c; | |
118 | ||
119 | /* | |
120 | * Only read source character once, in case it is | |
121 | * modified concurrently. | |
122 | */ | |
123 | c = CMM_LOAD_SHARED(src[count]); | |
124 | if (!c) | |
125 | break; | |
126 | lib_ring_buffer_do_copy(config, &dest[count], &c, 1); | |
127 | } | |
128 | return count; | |
129 | } | |
130 | ||
131 | /** | |
132 | * lib_ring_buffer_strcpy - write string data to a buffer backend | |
133 | * @config : ring buffer instance configuration | |
134 | * @ctx: ring buffer context. (input arguments only) | |
135 | * @src : source pointer to copy from | |
136 | * @len : length of data to copy | |
137 | * @pad : character to use for padding | |
138 | * | |
139 | * This function copies @len - 1 bytes of string data from a source | |
140 | * pointer to a buffer backend, followed by a terminating '\0' | |
141 | * character, at the current context offset. This is more or less a | |
142 | * buffer backend-specific strncpy() operation. If a terminating '\0' | |
143 | * character is found in @src before @len - 1 characters are copied, pad | |
144 | * the buffer with @pad characters (e.g. '#'). | |
145 | */ | |
00d0f8eb | 146 | static inline __attribute__((always_inline)) |
a44c74d9 MD |
147 | void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, |
148 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
149 | const char *src, size_t len, int pad) | |
150 | { | |
a44c74d9 MD |
151 | struct channel_backend *chanb = &ctx->chan->backend; |
152 | struct lttng_ust_shm_handle *handle = ctx->handle; | |
a3492932 | 153 | size_t count; |
a44c74d9 | 154 | size_t offset = ctx->buf_offset; |
a3492932 MD |
155 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
156 | void *p; | |
a44c74d9 MD |
157 | |
158 | if (caa_unlikely(!len)) | |
159 | return; | |
a44c74d9 MD |
160 | /* |
161 | * Underlying layer should never ask for writes across | |
162 | * subbuffers. | |
163 | */ | |
a3492932 MD |
164 | CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size); |
165 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); | |
166 | if (caa_unlikely(!backend_pages)) { | |
167 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
168 | return; | |
169 | } | |
170 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); | |
171 | if (caa_unlikely(!p)) | |
172 | return; | |
173 | ||
174 | count = lib_ring_buffer_do_strcpy(config, p, src, len - 1); | |
a44c74d9 MD |
175 | offset += count; |
176 | /* Padding */ | |
177 | if (caa_unlikely(count < len - 1)) { | |
178 | size_t pad_len = len - 1 - count; | |
179 | ||
a3492932 MD |
180 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
181 | if (caa_unlikely(!p)) | |
182 | return; | |
183 | lib_ring_buffer_do_memset(p, pad, pad_len); | |
a44c74d9 MD |
184 | offset += pad_len; |
185 | } | |
186 | /* Final '\0' */ | |
a3492932 MD |
187 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
188 | if (caa_unlikely(!p)) | |
189 | return; | |
190 | lib_ring_buffer_do_memset(p, '\0', 1); | |
a44c74d9 MD |
191 | ctx->buf_offset += len; |
192 | } | |
193 | ||
852c2936 MD |
194 | /* |
195 | * This accessor counts the number of unread records in a buffer. | |
196 | * It only provides a consistent value if no reads not writes are performed | |
197 | * concurrently. | |
198 | */ | |
199 | static inline | |
200 | unsigned long lib_ring_buffer_get_records_unread( | |
4cfec15c MD |
201 | const struct lttng_ust_lib_ring_buffer_config *config, |
202 | struct lttng_ust_lib_ring_buffer *buf, | |
38fae1d3 | 203 | struct lttng_ust_shm_handle *handle) |
852c2936 | 204 | { |
4cfec15c | 205 | struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend; |
15500a1b | 206 | unsigned long records_unread = 0, sb_bindex; |
852c2936 | 207 | unsigned int i; |
15500a1b | 208 | struct channel *chan; |
852c2936 | 209 | |
15500a1b MD |
210 | chan = shmp(handle, bufb->chan); |
211 | if (!chan) | |
212 | return 0; | |
213 | for (i = 0; i < chan->backend.num_subbuf; i++) { | |
214 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; | |
215 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
216 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
217 | ||
218 | wsb = shmp_index(handle, bufb->buf_wsb, i); | |
219 | if (!wsb) | |
220 | return 0; | |
221 | sb_bindex = subbuffer_id_get_index(config, wsb->id); | |
222 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
223 | if (!rpages) | |
224 | return 0; | |
225 | backend_pages = shmp(handle, rpages->shmp); | |
226 | if (!backend_pages) | |
227 | return 0; | |
228 | records_unread += v_read(config, &backend_pages->records_unread); | |
852c2936 MD |
229 | } |
230 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
15500a1b MD |
231 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
232 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
233 | ||
234 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
235 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
236 | if (!rpages) | |
237 | return 0; | |
238 | backend_pages = shmp(handle, rpages->shmp); | |
239 | if (!backend_pages) | |
240 | return 0; | |
241 | records_unread += v_read(config, &backend_pages->records_unread); | |
852c2936 MD |
242 | } |
243 | return records_unread; | |
244 | } | |
245 | ||
e92f3e28 | 246 | #endif /* _LTTNG_RING_BUFFER_BACKEND_H */ |