8d2795466bb32400beda37fd2757aa1b94cb5441
[lttng-tools.git] / src / bin / lttng-sessiond / manage-kernel.cpp
1 /*
2 * Copyright (C) 2011 EfficiOS Inc.
3 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 * Copyright (C) 2013 Jérémie Galarneau <jeremie.galarneau@efficios.com>
5 *
6 * SPDX-License-Identifier: GPL-2.0-only
7 *
8 */
9
10 #include <common/pipe.hpp>
11 #include <common/utils.hpp>
12
13 #include "manage-kernel.hpp"
14 #include "testpoint.hpp"
15 #include "health-sessiond.hpp"
16 #include "utils.hpp"
17 #include "thread.hpp"
18 #include "kernel.hpp"
19 #include "kernel-consumer.hpp"
20
21 namespace {
22 struct thread_notifiers {
23 struct lttng_pipe *quit_pipe;
24 int kernel_poll_pipe_read_fd;
25 };
26 } /* namespace */
27
28 /*
29 * Update the kernel poll set of all channel fd available over all tracing
30 * session. Add the wakeup pipe at the end of the set.
31 */
32 static int update_kernel_poll(struct lttng_poll_event *events)
33 {
34 int ret;
35 struct ltt_kernel_channel *channel;
36 struct ltt_session *session;
37 const struct ltt_session_list *session_list = session_get_list();
38
39 DBG("Updating kernel poll set");
40
41 session_lock_list();
42 cds_list_for_each_entry(session, &session_list->head, list) {
43 if (!session_get(session)) {
44 continue;
45 }
46 session_lock(session);
47 if (session->kernel_session == NULL) {
48 session_unlock(session);
49 session_put(session);
50 continue;
51 }
52
53 cds_list_for_each_entry(channel,
54 &session->kernel_session->channel_list.head, list) {
55 /* Add channel fd to the kernel poll set */
56 ret = lttng_poll_add(events, channel->fd, LPOLLIN | LPOLLRDNORM);
57 if (ret < 0) {
58 session_unlock(session);
59 session_put(session);
60 goto error;
61 }
62 DBG("Channel fd %d added to kernel set", channel->fd);
63 }
64 session_unlock(session);
65 session_put(session);
66 }
67 session_unlock_list();
68
69 return 0;
70
71 error:
72 session_unlock_list();
73 return -1;
74 }
75
76 /*
77 * Find the channel fd from 'fd' over all tracing session. When found, check
78 * for new channel stream and send those stream fds to the kernel consumer.
79 *
80 * Useful for CPU hotplug feature.
81 */
82 static int update_kernel_stream(int fd)
83 {
84 int ret = 0;
85 struct ltt_session *session;
86 struct ltt_kernel_session *ksess;
87 struct ltt_kernel_channel *channel;
88 const struct ltt_session_list *session_list = session_get_list();
89
90 DBG("Updating kernel streams for channel fd %d", fd);
91
92 session_lock_list();
93 cds_list_for_each_entry(session, &session_list->head, list) {
94 if (!session_get(session)) {
95 continue;
96 }
97 session_lock(session);
98 if (session->kernel_session == NULL) {
99 session_unlock(session);
100 session_put(session);
101 continue;
102 }
103 ksess = session->kernel_session;
104
105 cds_list_for_each_entry(channel,
106 &ksess->channel_list.head, list) {
107 struct lttng_ht_iter iter;
108 struct consumer_socket *socket;
109
110 if (channel->fd != fd) {
111 continue;
112 }
113 DBG("Channel found, updating kernel streams");
114 ret = kernel_open_channel_stream(channel);
115 if (ret < 0) {
116 goto error;
117 }
118 /* Update the stream global counter */
119 ksess->stream_count_global += ret;
120
121 /*
122 * Have we already sent fds to the consumer? If yes, it
123 * means that tracing is started so it is safe to send
124 * our updated stream fds.
125 */
126 if (ksess->consumer_fds_sent != 1
127 || ksess->consumer == NULL) {
128 ret = -1;
129 goto error;
130 }
131
132 rcu_read_lock();
133 cds_lfht_for_each_entry(ksess->consumer->socks->ht,
134 &iter.iter, socket, node.node) {
135 pthread_mutex_lock(socket->lock);
136 ret = kernel_consumer_send_channel_streams(socket,
137 channel, ksess,
138 session->output_traces ? 1 : 0);
139 pthread_mutex_unlock(socket->lock);
140 if (ret < 0) {
141 rcu_read_unlock();
142 goto error;
143 }
144 }
145 rcu_read_unlock();
146 }
147 session_unlock(session);
148 session_put(session);
149 }
150 session_unlock_list();
151 return ret;
152
153 error:
154 session_unlock(session);
155 session_put(session);
156 session_unlock_list();
157 return ret;
158 }
159
160 /*
161 * This thread manage event coming from the kernel.
162 *
163 * Features supported in this thread:
164 * -) CPU Hotplug
165 */
166 static void *thread_kernel_management(void *data)
167 {
168 int ret, i, pollfd, update_poll_flag = 1, err = -1;
169 uint32_t revents, nb_fd;
170 char tmp;
171 struct lttng_poll_event events;
172 struct thread_notifiers *notifiers = (thread_notifiers *) data;
173 const int quit_pipe_read_fd = lttng_pipe_get_readfd(notifiers->quit_pipe);
174
175 DBG("[thread] Thread manage kernel started");
176
177 health_register(the_health_sessiond, HEALTH_SESSIOND_TYPE_KERNEL);
178
179 /*
180 * This first step of the while is to clean this structure which could free
181 * non NULL pointers so initialize it before the loop.
182 */
183 lttng_poll_init(&events);
184
185 if (testpoint(sessiond_thread_manage_kernel)) {
186 goto error_testpoint;
187 }
188
189 health_code_update();
190
191 if (testpoint(sessiond_thread_manage_kernel_before_loop)) {
192 goto error_testpoint;
193 }
194
195 while (1) {
196 health_code_update();
197
198 if (update_poll_flag == 1) {
199 /* Clean events object. We are about to populate it again. */
200 lttng_poll_clean(&events);
201
202 ret = lttng_poll_create(&events, 2, LTTNG_CLOEXEC);
203 if (ret < 0) {
204 goto error_poll_create;
205 }
206
207 ret = lttng_poll_add(&events,
208 notifiers->kernel_poll_pipe_read_fd,
209 LPOLLIN);
210 if (ret < 0) {
211 goto error;
212 }
213
214 ret = lttng_poll_add(&events,
215 quit_pipe_read_fd,
216 LPOLLIN);
217 if (ret < 0) {
218 goto error;
219 }
220
221 /* This will add the available kernel channel if any. */
222 ret = update_kernel_poll(&events);
223 if (ret < 0) {
224 goto error;
225 }
226 update_poll_flag = 0;
227 }
228
229 DBG("Thread kernel polling");
230
231 /* Poll infinite value of time */
232 restart:
233 health_poll_entry();
234 ret = lttng_poll_wait(&events, -1);
235 DBG("Thread kernel return from poll on %d fds",
236 LTTNG_POLL_GETNB(&events));
237 health_poll_exit();
238 if (ret < 0) {
239 /*
240 * Restart interrupted system call.
241 */
242 if (errno == EINTR) {
243 goto restart;
244 }
245 goto error;
246 } else if (ret == 0) {
247 /* Should not happen since timeout is infinite */
248 ERR("Return value of poll is 0 with an infinite timeout.\n"
249 "This should not have happened! Continuing...");
250 continue;
251 }
252
253 nb_fd = ret;
254
255 for (i = 0; i < nb_fd; i++) {
256 /* Fetch once the poll data */
257 revents = LTTNG_POLL_GETEV(&events, i);
258 pollfd = LTTNG_POLL_GETFD(&events, i);
259
260 health_code_update();
261
262 if (pollfd == quit_pipe_read_fd) {
263 err = 0;
264 goto exit;
265 }
266
267 /* Check for data on kernel pipe */
268 if (revents & LPOLLIN) {
269 if (pollfd == notifiers->kernel_poll_pipe_read_fd) {
270 (void) lttng_read(notifiers->kernel_poll_pipe_read_fd,
271 &tmp, 1);
272 /*
273 * Ret value is useless here, if this pipe gets any actions an
274 * update is required anyway.
275 */
276 update_poll_flag = 1;
277 continue;
278 } else {
279 /*
280 * New CPU detected by the kernel. Adding kernel stream to
281 * kernel session and updating the kernel consumer
282 */
283 ret = update_kernel_stream(pollfd);
284 if (ret < 0) {
285 continue;
286 }
287 break;
288 }
289 } else if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
290 update_poll_flag = 1;
291 continue;
292 } else {
293 ERR("Unexpected poll events %u for sock %d", revents, pollfd);
294 goto error;
295 }
296 }
297 }
298
299 exit:
300 error:
301 lttng_poll_clean(&events);
302 error_poll_create:
303 error_testpoint:
304 if (err) {
305 health_error();
306 ERR("Health error occurred in %s", __func__);
307 WARN("Kernel thread died unexpectedly. "
308 "Kernel tracing can continue but CPU hotplug is disabled.");
309 }
310 health_unregister(the_health_sessiond);
311 DBG("Kernel thread dying");
312 return NULL;
313 }
314
315 static bool shutdown_kernel_management_thread(void *data)
316 {
317 struct thread_notifiers *notifiers = (thread_notifiers *) data;
318 const int write_fd = lttng_pipe_get_writefd(notifiers->quit_pipe);
319
320 return notify_thread_pipe(write_fd) == 1;
321 }
322
323 static void cleanup_kernel_management_thread(void *data)
324 {
325 struct thread_notifiers *notifiers = (thread_notifiers *) data;
326
327 lttng_pipe_destroy(notifiers->quit_pipe);
328 free(notifiers);
329 }
330
331 bool launch_kernel_management_thread(int kernel_poll_pipe_read_fd)
332 {
333 struct lttng_pipe *quit_pipe;
334 struct thread_notifiers *notifiers = NULL;
335 struct lttng_thread *thread;
336
337 notifiers = zmalloc<thread_notifiers>();
338 if (!notifiers) {
339 goto error_alloc;
340 }
341 quit_pipe = lttng_pipe_open(FD_CLOEXEC);
342 if (!quit_pipe) {
343 goto error;
344 }
345 notifiers->quit_pipe = quit_pipe;
346 notifiers->kernel_poll_pipe_read_fd = kernel_poll_pipe_read_fd;
347
348 thread = lttng_thread_create("Kernel management",
349 thread_kernel_management,
350 shutdown_kernel_management_thread,
351 cleanup_kernel_management_thread,
352 notifiers);
353 if (!thread) {
354 goto error;
355 }
356 lttng_thread_put(thread);
357 return true;
358 error:
359 cleanup_kernel_management_thread(notifiers);
360 error_alloc:
361 return false;
362 }
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