X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fmain.c;h=9c2458eb1a15a1bee49d1a1babe3d0390418390e;hp=f9b41d2707bd26aff4f95a72aa1885d2f2f09280;hb=524423d6b372147fd0a012700873d455fa4a0737;hpb=bc4b3ff16b26d5430fe701fd0680a157c65e21f8;ds=sidebyside

diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index f9b41d270..9c2458eb1 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