From e524d8399abc076190d6320811d7f7ff54e49a85 Mon Sep 17 00:00:00 2001
From: schneider <schneider@blinkenlichts.net>
Date: Wed, 15 Sep 2021 11:51:17 +0200
Subject: [PATCH] fix(pycardium): Fix potential race when systick counts from 1
to 0
---
pycardium/mphalport.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/pycardium/mphalport.c b/pycardium/mphalport.c
index c4ba6bdb1..ab3e0857c 100644
--- a/pycardium/mphalport.c
+++ b/pycardium/mphalport.c
@@ -166,13 +166,16 @@ void SysTick_Handler(void)
static uint64_t systick_get_us()
{
uint32_t val, count;
+ uint32_t irqsaved = __get_PRIMASK();
/* The asynchronous/slow clocking of the systick means that
* its value can jump to 0 before the interrupt is triggered.
* Simply wait until it is not 0 and then read the count. */
do {
+ __set_PRIMASK(0);
val = SysTick->VAL;
count = systick_count;
+ __set_PRIMASK(irqsaved);
} while (val == 0);
uint64_t us = count * SYSTICK_INTERVAL_US +
--
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