src/bin/lttng-relayd/thread-utils.cpp

   1 /*
   2  * Copyright (C) 2022 EfficiOS Inc.
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #include "lttng-relayd.hpp"
   9
  10 #include <common/compat/poll.hpp>
  11 #include <common/error.hpp>
  12 #include <common/fd-tracker/utils.hpp>
  13 #include <common/readwrite.hpp>
  14 #include <common/utils.hpp>
  15
  16 /*
  17  * Quit pipe for all threads. This permits a single cancellation point
  18  * for all threads when receiving an event on the pipe.
  19  */
  20 static int thread_quit_pipe[2] = { -1, -1 };
  21
  22 /*
  23  * Write to writable pipe used to notify a thread.
  24  */
  25 static int notify_thread_pipe(int wpipe)
  26 {
  27         const auto ret = lttng_write(wpipe, "!", 1);
  28
  29         if (ret < 1) {
  30                 PERROR("Failed to write to thread pipe");
  31                 return -1;
  32         }
  33
  34         return 0;
  35 }
  36
  37 /*
  38  * Initialize the thread quit pipe.
  39  *
  40  * Return -1 on error or 0 if all pipes are created.
  41  */
  42 int relayd_init_thread_quit_pipe()
  43 {
  44         return fd_tracker_util_pipe_open_cloexec(
  45                 the_fd_tracker, "Thread quit pipe", thread_quit_pipe);
  46 }
  47
  48 /*
  49  * Notify the threads to initiate shutdown.
  50  *
  51  * Return 0 on success or -1 on error.
  52  */
  53 int relayd_notify_thread_quit_pipe()
  54 {
  55         return notify_thread_pipe(thread_quit_pipe[1]);
  56 }
  57
  58 /*
  59  * Close the thread quit pipe.
  60  */
  61 void relayd_close_thread_quit_pipe()
  62 {
  63         if (thread_quit_pipe[0] != -1) {
  64                 (void) fd_tracker_util_pipe_close(the_fd_tracker, thread_quit_pipe);
  65         }
  66 }
  67
  68 /*
  69  * Return 1 if 'fd' is the thread quit pipe read fd.
  70  */
  71 bool relayd_is_thread_quit_pipe(const int fd)
  72 {
  73         return (fd == thread_quit_pipe[0]);
  74 }
  75
  76 /*
  77  * Create a poll set with O_CLOEXEC and add the thread quit pipe to the set.
  78  */
  79 int create_named_thread_poll_set(struct lttng_poll_event *events, int size, const char *name)
  80 {
  81         if (events == nullptr || size == 0) {
  82                 return -1;
  83         }
  84
  85         const auto create_ret =
  86                 fd_tracker_util_poll_create(the_fd_tracker, name, events, 1, LTTNG_CLOEXEC);
  87         if (create_ret) {
  88                 PERROR("Failed to create \"%s\" poll file descriptor", name);
  89                 return -1;
  90         }
  91
  92         /* Add thread quit pipe to monitored events. */
  93         const auto poll_add_ret = lttng_poll_add(events, thread_quit_pipe[0], LPOLLIN);
  94         if (poll_add_ret < 0) {
  95                 return -1;
  96         }
  97
  98         return 0;
  99 }