From 304f4ec7d4426f8b549412dde29fc5b2eb4f9af8 Mon Sep 17 00:00:00 2001
From: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
Date: Fri, 25 Sep 2020 13:51:38 +0200
Subject: [PATCH] cpu/cortexm_common: flush pipeline after PendSV

https://interrupt.memfault.com/blog/arm-cortex-m-exceptions-and-nvic#pendsv-example
---
 cpu/cortexm_common/thread_arch.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/cpu/cortexm_common/thread_arch.c b/cpu/cortexm_common/thread_arch.c
index 145372019d..19a1923e64 100644
--- a/cpu/cortexm_common/thread_arch.c
+++ b/cpu/cortexm_common/thread_arch.c
@@ -297,6 +297,9 @@ void thread_yield_higher(void)
     /* trigger the PENDSV interrupt to run scheduler and schedule new thread if
      * applicable */
     SCB->ICSR = SCB_ICSR_PENDSVSET_Msk;
+    /* flush the pipeline. Otherwise we risk that subsequent instructions are
+     * executed before the IRQ has actually triggered */
+    __ISB();
 }
 
 void __attribute__((naked)) __attribute__((used)) isr_pendsv(void) {