X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fmain.c;h=e032e037c3ebf933f0caa216cd292578fbb7e9ae;hb=3044f922f5125b490a1815d5913f8b9d00e21e9a;hp=f9b41d2707bd26aff4f95a72aa1885d2f2f09280;hpb=bc4b3ff16b26d5430fe701fd0680a157c65e21f8;p=lttng-tools.git

diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index f9b41d270..e032e037c 100644
--- a/src/bin/lttng-sessiond/main.c
+++ b/src/bin/lttng-sessiond/main.c
@@ -366,10 +366,21 @@ LTTNG_HIDDEN
 void sessiond_notify_ready(void)
 {
 	/*
-	 * The _return variant is used since the implied memory barriers are
-	 * required.
+	 * This memory barrier is paired with the one performed by
+	 * the client thread after it has seen that 'lttng_sessiond_ready' is 0.
+	 *
+	 * The purpose of these memory barriers is to ensure that all
+	 * initialization operations of the various threads that call this
+	 * function to signal that they are ready are commited/published
+	 * before the client thread can see the 'lttng_sessiond_ready' counter
+	 * reach 0.
+	 *
+	 * Note that this could be a 'write' memory barrier, but a full barrier
+	 * is used in case the code using this utility changes. The performance
+	 * implications of this choice are minimal since this is a slow path.
 	 */
-	(void) uatomic_sub_return(&lttng_sessiond_ready, 1);
+	cmm_smp_mb();
+	uatomic_sub(&lttng_sessiond_ready, 1);
 }
 
 static
@@ -4563,8 +4574,17 @@ static void *thread_manage_clients(void *data)
 		if (ret > 0 || (ret < 0 && errno != EINTR)) {
 			goto exit;
 		}
-		cmm_smp_rmb();
 	}
+	/*
+	 * This barrier is paired with the one in sessiond_notify_ready() to
+	 * ensure that loads accessing data initialized by the other threads,
+	 * on which this thread was waiting, are not performed before this point.
+	 *
+	 * Note that this could be a 'read' memory barrier, but a full barrier
+	 * is used in case the code changes. The performance implications of
+	 * this choice are minimal since this is a slow path.
+	 */
+	cmm_smp_mb();
 
 	/* This testpoint is after we signal readiness to the parent. */
 	if (testpoint(sessiond_thread_manage_clients)) {
@@ -5810,6 +5830,12 @@ int main(int argc, char **argv)
 		goto exit_set_signal_handler;
 	}
 
+	/*
+	 * Init config from environment variables.
+	 * Command line option override env configuration per-doc. Do env first.
+	 */
+	sessiond_config_apply_env_config(&config);
+
 	/*
 	 * Parse arguments and load the daemon configuration file.
 	 *
@@ -5824,9 +5850,6 @@ int main(int argc, char **argv)
 		goto exit_options;
 	}
 
-	/* Init config from environment variables. */
-	sessiond_config_apply_env_config(&config);
-
 	/*
 	 * Resolve all paths received as arguments, configuration option, or
 	 * through environment variable as absolute paths. This is necessary