From 375cad38df9f548e3bbf59ca6ceae8c6d6f6a57f Mon Sep 17 00:00:00 2001
From: Leandro Lanzieri <leandro.lanzieri@haw-hamburg.de>
Date: Fri, 15 May 2020 11:16:47 +0200
Subject: [PATCH] gnrc/sixlowpan: 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/sixlowpan/config.h         | 17 ++++++++++++++---
 sys/net/gnrc/network_layer/sixlowpan/Kconfig    | 10 +++++++---
 .../network_layer/sixlowpan/gnrc_sixlowpan.c    |  4 ++--
 3 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/sys/include/net/gnrc/sixlowpan/config.h b/sys/include/net/gnrc/sixlowpan/config.h
index 686d48406f..3701d89bb5 100644
--- a/sys/include/net/gnrc/sixlowpan/config.h
+++ b/sys/include/net/gnrc/sixlowpan/config.h
@@ -43,10 +43,14 @@ extern "C" {
 #endif
 
 /**
- * @brief   Default message queue size to use for the 6LoWPAN thread.
+ * @brief   Default message queue size to use for the 6LoWPAN 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_SIXLOWPAN_MSG_QUEUE_SIZE
-#define CONFIG_GNRC_SIXLOWPAN_MSG_QUEUE_SIZE       (8U)
+#ifndef CONFIG_GNRC_SIXLOWPAN_MSG_QUEUE_SIZE_EXP
+#define CONFIG_GNRC_SIXLOWPAN_MSG_QUEUE_SIZE_EXP   (3U)
 #endif
 
 /**
@@ -307,6 +311,13 @@ extern "C" {
 #endif
 /** @} */
 
+/**
+ * @brief   Message queue size to use for the 6LoWPAN thread.
+ */
+#ifndef GNRC_SIXLOWPAN_MSG_QUEUE_SIZE
+#define GNRC_SIXLOWPAN_MSG_QUEUE_SIZE    (1 << CONFIG_GNRC_SIXLOWPAN_MSG_QUEUE_SIZE_EXP)
+#endif
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/sys/net/gnrc/network_layer/sixlowpan/Kconfig b/sys/net/gnrc/network_layer/sixlowpan/Kconfig
index d38ae846f9..9aa2776697 100644
--- a/sys/net/gnrc/network_layer/sixlowpan/Kconfig
+++ b/sys/net/gnrc/network_layer/sixlowpan/Kconfig
@@ -16,8 +16,12 @@ if KCONFIG_MODULE_GNRC_SIXLOWPAN
 rsource "frag/Kconfig"
 rsource "nd/Kconfig"
 
-config GNRC_SIXLOWPAN_MSG_QUEUE_SIZE
-    int "Message queue size for the 6LoWPAN thread"
-    default 8
+config GNRC_SIXLOWPAN_MSG_QUEUE_SIZE_EXP
+    int "Exponent for the message queue size for the 6LoWPAN 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_SIXLOWPAN
diff --git a/sys/net/gnrc/network_layer/sixlowpan/gnrc_sixlowpan.c b/sys/net/gnrc/network_layer/sixlowpan/gnrc_sixlowpan.c
index 5ea018b5b7..1ae7027b5c 100644
--- a/sys/net/gnrc/network_layer/sixlowpan/gnrc_sixlowpan.c
+++ b/sys/net/gnrc/network_layer/sixlowpan/gnrc_sixlowpan.c
@@ -308,12 +308,12 @@ static void _send(gnrc_pktsnip_t *pkt)
 
 static void *_event_loop(void *args)
 {
-    msg_t msg, reply, msg_q[CONFIG_GNRC_SIXLOWPAN_MSG_QUEUE_SIZE];
+    msg_t msg, reply, msg_q[GNRC_SIXLOWPAN_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_SIXLOWPAN_MSG_QUEUE_SIZE);
+    msg_init_queue(msg_q, GNRC_SIXLOWPAN_MSG_QUEUE_SIZE);
 
     /* register interest in all 6LoWPAN packets */
     gnrc_netreg_register(GNRC_NETTYPE_SIXLOWPAN, &me_reg);