src/bin/lttng-sessiond/manage-kernel.c

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