src/bin/lttng-sessiond/manage-apps.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 "health-sessiond.hpp"
  11 #include "manage-apps.hpp"
  12 #include "testpoint.hpp"
  13 #include "thread.hpp"
  14 #include "utils.hpp"
  15
  16 #include <fcntl.h>
  17
  18 namespace {
  19 struct thread_notifiers {
  20         struct lttng_pipe *quit_pipe;
  21         int apps_cmd_pipe_read_fd;
  22 };
  23 } /* namespace */
  24
  25 static void cleanup_application_management_thread(void *data)
  26 {
  27         struct thread_notifiers *notifiers = (thread_notifiers *) data;
  28
  29         lttng_pipe_destroy(notifiers->quit_pipe);
  30         free(notifiers);
  31 }
  32
  33 /*
  34  * This thread receives application command sockets (FDs) on the
  35  * apps_cmd_pipe and waits (polls) on them until they are closed
  36  * or an error occurs.
  37  *
  38  * At that point, it flushes the data (tracing and metadata) associated
  39  * with this application and tears down ust app sessions and other
  40  * associated data structures through ust_app_unregister_by_socket().
  41  *
  42  * Note that this thread never sends commands to the applications
  43  * through the command sockets; it merely listens for hang-ups
  44  * and errors on those sockets and cleans-up as they occur.
  45  */
  46 static void *thread_application_management(void *data)
  47 {
  48         int i, ret, err = -1;
  49         ssize_t size_ret;
  50         uint32_t nb_fd;
  51         struct lttng_poll_event events;
  52         struct thread_notifiers *notifiers = (thread_notifiers *) data;
  53         const auto thread_quit_pipe_fd = lttng_pipe_get_readfd(notifiers->quit_pipe);
  54
  55         DBG("[thread] Manage application started");
  56
  57         rcu_register_thread();
  58         rcu_thread_online();
  59
  60         health_register(the_health_sessiond, HEALTH_SESSIOND_TYPE_APP_MANAGE);
  61
  62         if (testpoint(sessiond_thread_manage_apps)) {
  63                 goto error_testpoint;
  64         }
  65
  66         health_code_update();
  67
  68         ret = lttng_poll_create(&events, 2, LTTNG_CLOEXEC);
  69         if (ret < 0) {
  70                 goto error_poll_create;
  71         }
  72
  73         ret = lttng_poll_add(&events, notifiers->apps_cmd_pipe_read_fd, LPOLLIN | LPOLLRDHUP);
  74         if (ret < 0) {
  75                 goto error;
  76         }
  77
  78         ret = lttng_poll_add(&events, thread_quit_pipe_fd, LPOLLIN);
  79         if (ret < 0) {
  80                 goto error;
  81         }
  82
  83         if (testpoint(sessiond_thread_manage_apps_before_loop)) {
  84                 goto error;
  85         }
  86
  87         health_code_update();
  88
  89         while (true) {
  90                 DBG("Apps thread polling");
  91
  92                 /* Inifinite blocking call, waiting for transmission */
  93         restart:
  94                 health_poll_entry();
  95                 ret = lttng_poll_wait(&events, -1);
  96                 DBG("Apps thread return from poll on %d fds", LTTNG_POLL_GETNB(&events));
  97                 health_poll_exit();
  98                 if (ret < 0) {
  99                         /*
 100                          * Restart interrupted system call.
 101                          */
 102                         if (errno == EINTR) {
 103                                 goto restart;
 104                         }
 105                         goto error;
 106                 }
 107
 108                 nb_fd = ret;
 109
 110                 for (i = 0; i < nb_fd; i++) {
 111                         /* Fetch once the poll data */
 112                         const auto revents = LTTNG_POLL_GETEV(&events, i);
 113                         const auto pollfd = LTTNG_POLL_GETFD(&events, i);
 114
 115                         health_code_update();
 116
 117                         /* Activity on thread quit pipe, exiting. */
 118                         if (pollfd == thread_quit_pipe_fd) {
 119                                 DBG("Activity on thread quit pipe");
 120                                 err = 0;
 121                                 goto exit;
 122                         }
 123
 124                         if (pollfd == notifiers->apps_cmd_pipe_read_fd) {
 125                                 /* Inspect the apps cmd pipe */
 126                                 if (revents & LPOLLIN) {
 127                                         int sock;
 128
 129                                         /* Empty pipe */
 130                                         size_ret = lttng_read(notifiers->apps_cmd_pipe_read_fd,
 131                                                               &sock,
 132                                                               sizeof(sock));
 133                                         if (size_ret < sizeof(sock)) {
 134                                                 PERROR("read apps cmd pipe");
 135                                                 goto error;
 136                                         }
 137
 138                                         health_code_update();
 139
 140                                         /*
 141                                          * Since this is a command socket (write then read),
 142                                          * we only monitor the error events of the socket.
 143                                          */
 144                                         ret = lttng_poll_add(&events, sock, LPOLLRDHUP);
 145                                         if (ret < 0) {
 146                                                 goto error;
 147                                         }
 148
 149                                         DBG("Apps with sock %d added to poll set", sock);
 150                                 } else if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
 151                                         ERR("Apps command pipe error");
 152                                         goto error;
 153                                 } else {
 154                                         ERR("Unknown poll events %u for sock %d", revents, pollfd);
 155                                         goto error;
 156                                 }
 157                         } else {
 158                                 /*
 159                                  * At this point, we know that a registered application made
 160                                  * the event at poll_wait.
 161                                  */
 162                                 if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
 163                                         /* Removing from the poll set */
 164                                         ret = lttng_poll_del(&events, pollfd);
 165                                         if (ret < 0) {
 166                                                 goto error;
 167                                         }
 168
 169                                         /* Socket closed on remote end. */
 170                                         ust_app_unregister_by_socket(pollfd);
 171                                 } else {
 172                                         ERR("Unexpected poll events %u for sock %d",
 173                                             revents,
 174                                             pollfd);
 175                                         goto error;
 176                                 }
 177                         }
 178
 179                         health_code_update();
 180                 }
 181         }
 182
 183 exit:
 184 error:
 185         lttng_poll_clean(&events);
 186 error_poll_create:
 187 error_testpoint:
 188
 189         /*
 190          * We don't clean the UST app hash table here since already registered
 191          * applications can still be controlled so let them be until the session
 192          * daemon dies or the applications stop.
 193          */
 194
 195         if (err) {
 196                 health_error();
 197                 ERR("Health error occurred in %s", __func__);
 198         }
 199         health_unregister(the_health_sessiond);
 200         DBG("Application communication apps thread cleanup complete");
 201         rcu_thread_offline();
 202         rcu_unregister_thread();
 203         return nullptr;
 204 }
 205
 206 static bool shutdown_application_management_thread(void *data)
 207 {
 208         struct thread_notifiers *notifiers = (thread_notifiers *) data;
 209         const int write_fd = lttng_pipe_get_writefd(notifiers->quit_pipe);
 210
 211         return notify_thread_pipe(write_fd) == 1;
 212 }
 213
 214 bool launch_application_management_thread(int apps_cmd_pipe_read_fd)
 215 {
 216         struct lttng_pipe *quit_pipe;
 217         struct thread_notifiers *notifiers = nullptr;
 218         struct lttng_thread *thread;
 219
 220         notifiers = zmalloc<thread_notifiers>();
 221         if (!notifiers) {
 222                 goto error_alloc;
 223         }
 224         quit_pipe = lttng_pipe_open(FD_CLOEXEC);
 225         if (!quit_pipe) {
 226                 goto error;
 227         }
 228         notifiers->quit_pipe = quit_pipe;
 229         notifiers->apps_cmd_pipe_read_fd = apps_cmd_pipe_read_fd;
 230
 231         thread = lttng_thread_create("UST application management",
 232                                      thread_application_management,
 233                                      shutdown_application_management_thread,
 234                                      cleanup_application_management_thread,
 235                                      notifiers);
 236         if (!thread) {
 237                 goto error;
 238         }
 239
 240         lttng_thread_put(thread);
 241         return true;
 242 error:
 243         cleanup_application_management_thread(notifiers);
 244 error_alloc:
 245         return false;
 246 }