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