1 #ifndef _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
2 #define _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
5 * linux/ringbuffer/frontend_internal.h
7 * Ring Buffer Library Synchronization Header (internal helpers).
9 * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
26 * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
28 * See ring_buffer_frontend.c for more information on wait-free algorithms.
31 #include <wrapper/ringbuffer/config.h>
32 #include <wrapper/ringbuffer/backend_types.h>
33 #include <wrapper/ringbuffer/frontend_types.h>
34 #include <lib/prio_heap/lttng_prio_heap.h> /* For per-CPU read-side iterator */
36 /* Buffer offset macros */
38 /* buf_trunc mask selects only the buffer number. */
40 unsigned long buf_trunc(unsigned long offset
, struct channel
*chan
)
42 return offset
& ~(chan
->backend
.buf_size
- 1);
46 /* Select the buffer number value (counter). */
48 unsigned long buf_trunc_val(unsigned long offset
, struct channel
*chan
)
50 return buf_trunc(offset
, chan
) >> chan
->backend
.buf_size_order
;
53 /* buf_offset mask selects only the offset within the current buffer. */
55 unsigned long buf_offset(unsigned long offset
, struct channel
*chan
)
57 return offset
& (chan
->backend
.buf_size
- 1);
60 /* subbuf_offset mask selects the offset within the current subbuffer. */
62 unsigned long subbuf_offset(unsigned long offset
, struct channel
*chan
)
64 return offset
& (chan
->backend
.subbuf_size
- 1);
67 /* subbuf_trunc mask selects the subbuffer number. */
69 unsigned long subbuf_trunc(unsigned long offset
, struct channel
*chan
)
71 return offset
& ~(chan
->backend
.subbuf_size
- 1);
74 /* subbuf_align aligns the offset to the next subbuffer. */
76 unsigned long subbuf_align(unsigned long offset
, struct channel
*chan
)
78 return (offset
+ chan
->backend
.subbuf_size
)
79 & ~(chan
->backend
.subbuf_size
- 1);
82 /* subbuf_index returns the index of the current subbuffer within the buffer. */
84 unsigned long subbuf_index(unsigned long offset
, struct channel
*chan
)
86 return buf_offset(offset
, chan
) >> chan
->backend
.subbuf_size_order
;
90 * Last TSC comparison functions. Check if the current TSC overflows tsc_bits
91 * bits from the last TSC read. When overflows are detected, the full 64-bit
92 * timestamp counter should be written in the record header. Reads and writes
93 * last_tsc atomically.
96 #if (BITS_PER_LONG == 32)
98 void save_last_tsc(const struct lib_ring_buffer_config
*config
,
99 struct lib_ring_buffer
*buf
, u64 tsc
)
101 if (config
->tsc_bits
== 0 || config
->tsc_bits
== 64)
105 * Ensure the compiler performs this update in a single instruction.
107 v_set(config
, &buf
->last_tsc
, (unsigned long)(tsc
>> config
->tsc_bits
));
111 int last_tsc_overflow(const struct lib_ring_buffer_config
*config
,
112 struct lib_ring_buffer
*buf
, u64 tsc
)
114 unsigned long tsc_shifted
;
116 if (config
->tsc_bits
== 0 || config
->tsc_bits
== 64)
119 tsc_shifted
= (unsigned long)(tsc
>> config
->tsc_bits
);
120 if (unlikely(tsc_shifted
121 - (unsigned long)v_read(config
, &buf
->last_tsc
)))
128 void save_last_tsc(const struct lib_ring_buffer_config
*config
,
129 struct lib_ring_buffer
*buf
, u64 tsc
)
131 if (config
->tsc_bits
== 0 || config
->tsc_bits
== 64)
134 v_set(config
, &buf
->last_tsc
, (unsigned long)tsc
);
138 int last_tsc_overflow(const struct lib_ring_buffer_config
*config
,
139 struct lib_ring_buffer
*buf
, u64 tsc
)
141 if (config
->tsc_bits
== 0 || config
->tsc_bits
== 64)
144 if (unlikely((tsc
- v_read(config
, &buf
->last_tsc
))
145 >> config
->tsc_bits
))
153 int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx
*ctx
);
156 void lib_ring_buffer_switch_slow(struct lib_ring_buffer
*buf
,
157 enum switch_mode mode
);
160 void lib_ring_buffer_check_deliver_slow(const struct lib_ring_buffer_config
*config
,
161 struct lib_ring_buffer
*buf
,
162 struct channel
*chan
,
163 unsigned long offset
,
164 unsigned long commit_count
,
169 void lib_ring_buffer_switch_remote(struct lib_ring_buffer
*buf
);
171 void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer
*buf
);
173 /* Buffer write helpers */
176 void lib_ring_buffer_reserve_push_reader(struct lib_ring_buffer
*buf
,
177 struct channel
*chan
,
178 unsigned long offset
)
180 unsigned long consumed_old
, consumed_new
;
183 consumed_old
= atomic_long_read(&buf
->consumed
);
185 * If buffer is in overwrite mode, push the reader consumed
186 * count if the write position has reached it and we are not
187 * at the first iteration (don't push the reader farther than
188 * the writer). This operation can be done concurrently by many
189 * writers in the same buffer, the writer being at the farthest
190 * write position sub-buffer index in the buffer being the one
191 * which will win this loop.
193 if (unlikely(subbuf_trunc(offset
, chan
)
194 - subbuf_trunc(consumed_old
, chan
)
195 >= chan
->backend
.buf_size
))
196 consumed_new
= subbuf_align(consumed_old
, chan
);
199 } while (unlikely(atomic_long_cmpxchg(&buf
->consumed
, consumed_old
,
200 consumed_new
) != consumed_old
));
204 int lib_ring_buffer_pending_data(const struct lib_ring_buffer_config
*config
,
205 struct lib_ring_buffer
*buf
,
206 struct channel
*chan
)
208 return !!subbuf_offset(v_read(config
, &buf
->offset
), chan
);
212 unsigned long lib_ring_buffer_get_data_size(const struct lib_ring_buffer_config
*config
,
213 struct lib_ring_buffer
*buf
,
216 return subbuffer_get_data_size(config
, &buf
->backend
, idx
);
220 * Check if all space reservation in a buffer have been committed. This helps
221 * knowing if an execution context is nested (for per-cpu buffers only).
222 * This is a very specific ftrace use-case, so we keep this as "internal" API.
225 int lib_ring_buffer_reserve_committed(const struct lib_ring_buffer_config
*config
,
226 struct lib_ring_buffer
*buf
,
227 struct channel
*chan
)
229 unsigned long offset
, idx
, commit_count
;
231 CHAN_WARN_ON(chan
, config
->alloc
!= RING_BUFFER_ALLOC_PER_CPU
);
232 CHAN_WARN_ON(chan
, config
->sync
!= RING_BUFFER_SYNC_PER_CPU
);
235 * Read offset and commit count in a loop so they are both read
236 * atomically wrt interrupts. By deal with interrupt concurrency by
237 * restarting both reads if the offset has been pushed. Note that given
238 * we only have to deal with interrupt concurrency here, an interrupt
239 * modifying the commit count will also modify "offset", so it is safe
240 * to only check for offset modifications.
243 offset
= v_read(config
, &buf
->offset
);
244 idx
= subbuf_index(offset
, chan
);
245 commit_count
= v_read(config
, &buf
->commit_hot
[idx
].cc
);
246 } while (offset
!= v_read(config
, &buf
->offset
));
248 return ((buf_trunc(offset
, chan
) >> chan
->backend
.num_subbuf_order
)
249 - (commit_count
& chan
->commit_count_mask
) == 0);
253 * Receive end of subbuffer TSC as parameter. It has been read in the
254 * space reservation loop of either reserve or switch, which ensures it
255 * progresses monotonically with event records in the buffer. Therefore,
256 * it ensures that the end timestamp of a subbuffer is <= begin
257 * timestamp of the following subbuffers.
260 void lib_ring_buffer_check_deliver(const struct lib_ring_buffer_config
*config
,
261 struct lib_ring_buffer
*buf
,
262 struct channel
*chan
,
263 unsigned long offset
,
264 unsigned long commit_count
,
268 unsigned long old_commit_count
= commit_count
269 - chan
->backend
.subbuf_size
;
271 /* Check if all commits have been done */
272 if (unlikely((buf_trunc(offset
, chan
) >> chan
->backend
.num_subbuf_order
)
273 - (old_commit_count
& chan
->commit_count_mask
) == 0))
274 lib_ring_buffer_check_deliver_slow(config
, buf
, chan
, offset
,
275 commit_count
, idx
, tsc
);
279 * lib_ring_buffer_write_commit_counter
281 * For flight recording. must be called after commit.
282 * This function increments the subbuffer's commit_seq counter each time the
283 * commit count reaches back the reserve offset (modulo subbuffer size). It is
284 * useful for crash dump.
287 void lib_ring_buffer_write_commit_counter(const struct lib_ring_buffer_config
*config
,
288 struct lib_ring_buffer
*buf
,
289 struct channel
*chan
,
290 unsigned long buf_offset
,
291 unsigned long commit_count
,
292 struct commit_counters_hot
*cc_hot
)
294 unsigned long commit_seq_old
;
296 if (config
->oops
!= RING_BUFFER_OOPS_CONSISTENCY
)
300 * subbuf_offset includes commit_count_mask. We can simply
301 * compare the offsets within the subbuffer without caring about
302 * buffer full/empty mismatch because offset is never zero here
303 * (subbuffer header and record headers have non-zero length).
305 if (unlikely(subbuf_offset(buf_offset
- commit_count
, chan
)))
308 commit_seq_old
= v_read(config
, &cc_hot
->seq
);
309 if (likely((long) (commit_seq_old
- commit_count
) < 0))
310 v_set(config
, &cc_hot
->seq
, commit_count
);
313 extern int lib_ring_buffer_create(struct lib_ring_buffer
*buf
,
314 struct channel_backend
*chanb
, int cpu
);
315 extern void lib_ring_buffer_free(struct lib_ring_buffer
*buf
);
317 /* Keep track of trap nesting inside ring buffer code */
318 DECLARE_PER_CPU(unsigned int, lib_ring_buffer_nesting
);
320 #endif /* _LIB_RING_BUFFER_FRONTEND_INTERNAL_H */