Standardize quit pipes behavior

[lttng-tools.git] / src / bin / lttng-relayd / thread-utils.cpp

diff --git a/src/bin/lttng-relayd/thread-utils.cpp b/src/bin/lttng-relayd/thread-utils.cpp
new file mode 100644 (file)
index 0000000..d469f90
--- /dev/null
+++ b/src/bin/lttng-relayd/thread-utils.cpp
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2022 EfficiOS Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ */
+
+#include "lttng-relayd.hpp"
+
+#include <common/compat/poll.hpp>
+#include <common/error.hpp>
+#include <common/fd-tracker/utils.hpp>
+#include <common/readwrite.hpp>
+#include <common/utils.hpp>
+
+/*
+ * Quit pipe for all threads. This permits a single cancellation point
+ * for all threads when receiving an event on the pipe.
+ */
+static int thread_quit_pipe[2] = { -1, -1 };
+
+/*
+ * Write to writable pipe used to notify a thread.
+ */
+static int notify_thread_pipe(int wpipe)
+{
+       const auto ret = lttng_write(wpipe, "!", 1);
+
+       if (ret < 1) {
+               PERROR("Failed to write to thread pipe");
+               return -1;
+       }
+
+       return 0;
+}
+
+/*
+ * Initialize the thread quit pipe.
+ *
+ * Return -1 on error or 0 if all pipes are created.
+ */
+int relayd_init_thread_quit_pipe(void)
+{
+       return fd_tracker_util_pipe_open_cloexec(
+                       the_fd_tracker, "Thread quit pipe", thread_quit_pipe);
+}
+
+/*
+ * Notify the threads to initiate shutdown.
+ *
+ * Return 0 on success or -1 on error.
+ */
+int relayd_notify_thread_quit_pipe(void)
+{
+       return notify_thread_pipe(thread_quit_pipe[1]);
+}
+
+/*
+ * Close the thread quit pipe.
+ */
+void relayd_close_thread_quit_pipe(void)
+{
+       if (thread_quit_pipe[0] != -1) {
+               (void) fd_tracker_util_pipe_close(
+                               the_fd_tracker, thread_quit_pipe);
+       }
+}
+
+/*
+ * Return 1 if 'fd' is the thread quit pipe read fd.
+ */
+bool relayd_is_thread_quit_pipe(const int fd)
+{
+       return (fd == thread_quit_pipe[0]);
+}
+
+/*
+ * Create a poll set with O_CLOEXEC and add the thread quit pipe to the set.
+ */
+int create_named_thread_poll_set(struct lttng_poll_event *events,
+               int size, const char *name)
+{
+       if (events == NULL || size == 0) {
+               return -1;
+       }
+
+       const auto create_ret = fd_tracker_util_poll_create(the_fd_tracker,
+                       name, events, 1, LTTNG_CLOEXEC);
+       if (create_ret) {
+               PERROR("Failed to create \"%s\" poll file descriptor", name);
+               return -1;
+       }
+
+       /* Add thread quit pipe to monitored events. */
+       const auto poll_add_ret = lttng_poll_add(events, thread_quit_pipe[0], LPOLLIN | LPOLLERR);
+       if (poll_add_ret < 0) {
+               return -1;
+       }
+
+       return 0;
+}