From b0168f5fdd57fe8f9c0345da9b2837b90e175425 Mon Sep 17 00:00:00 2001
From: Leandro Lanzieri <leandro.lanzieri@haw-hamburg.de>
Date: Fri, 15 May 2020 09:47:09 +0200
Subject: [PATCH] gnrc/ipv6: Configure queue size with exponent

This changes the configuration macro to be the exponent of 2^n, as the
message queue size needs to be always power of 2.
---
 sys/include/net/gnrc/ipv6.h                 | 18 +++++++++++++++---
 sys/net/gnrc/network_layer/ipv6/Kconfig     | 10 +++++++---
 sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c |  4 ++--
 3 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/sys/include/net/gnrc/ipv6.h b/sys/include/net/gnrc/ipv6.h
index d5d10b635b..e230824a03 100644
--- a/sys/include/net/gnrc/ipv6.h
+++ b/sys/include/net/gnrc/ipv6.h
@@ -138,10 +138,15 @@ extern "C" {
 #endif
 
 /**
- * @brief   Default message queue size to use for the IPv6 thread.
+ * @brief   Default message queue size to use for the IPv6 thread (as exponent
+ *          of 2^n).
+ *
+ *          As the queue size ALWAYS needs to be power of two, this option
+ *          represents the exponent of 2^n, which will be used as the size of
+ *          the queue.
  */
-#ifndef CONFIG_GNRC_IPV6_MSG_QUEUE_SIZE
-#define CONFIG_GNRC_IPV6_MSG_QUEUE_SIZE    (8U)
+#ifndef CONFIG_GNRC_IPV6_MSG_QUEUE_SIZE_EXP
+#define CONFIG_GNRC_IPV6_MSG_QUEUE_SIZE_EXP    (3U)
 #endif
 
 #ifdef DOXYGEN
@@ -164,6 +169,13 @@ extern "C" {
 #endif /* DOXYGEN */
 /** @} */
 
+/**
+ * @brief Message queue size to use for the IPv6 thread.
+ */
+#ifndef GNRC_IPV6_MSG_QUEUE_SIZE
+#define GNRC_IPV6_MSG_QUEUE_SIZE    (1 << CONFIG_GNRC_IPV6_MSG_QUEUE_SIZE_EXP)
+#endif
+
 /**
  * @brief   The PID to the IPv6 thread.
  *
diff --git a/sys/net/gnrc/network_layer/ipv6/Kconfig b/sys/net/gnrc/network_layer/ipv6/Kconfig
index 06fa33b52c..13c713b45f 100644
--- a/sys/net/gnrc/network_layer/ipv6/Kconfig
+++ b/sys/net/gnrc/network_layer/ipv6/Kconfig
@@ -14,9 +14,13 @@ menuconfig KCONFIG_MODULE_GNRC_IPV6
 
 if KCONFIG_MODULE_GNRC_IPV6
 
-config GNRC_IPV6_MSG_QUEUE_SIZE
-    int "Default message queue size to use for the IPv6 thread"
-    default 8
+config GNRC_IPV6_MSG_QUEUE_SIZE_EXP
+    int "Exponent for the message queue size used for the IPv6 thread (as 2^n)"
+    default 3
+    help
+        As the queue size ALWAYS needs to be power of two, this option
+        represents the exponent of 2^n, which will be used as the size of
+        the queue.
 
 endif # KCONFIG_MODULE_GNRC_IPV6
 
diff --git a/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c b/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
index 55961e70de..b774a669f6 100644
--- a/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
+++ b/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
@@ -173,12 +173,12 @@ static void _dispatch_next_header(gnrc_pktsnip_t *pkt, unsigned nh,
 
 static void *_event_loop(void *args)
 {
-    msg_t msg, reply, msg_q[CONFIG_GNRC_IPV6_MSG_QUEUE_SIZE];
+    msg_t msg, reply, msg_q[GNRC_IPV6_MSG_QUEUE_SIZE];
     gnrc_netreg_entry_t me_reg = GNRC_NETREG_ENTRY_INIT_PID(GNRC_NETREG_DEMUX_CTX_ALL,
                                                             sched_active_pid);
 
     (void)args;
-    msg_init_queue(msg_q, CONFIG_GNRC_IPV6_MSG_QUEUE_SIZE);
+    msg_init_queue(msg_q, GNRC_IPV6_MSG_QUEUE_SIZE);
 
     /* initialize fragmentation data-structures */
 #ifdef MODULE_GNRC_IPV6_EXT_FRAG