tests/deferred_yield_higher: initial commit

This test verifies that a thread can call `thread_yield_higher()` with IRQs
disabled, and that the actual context switch is deferred until IRQs are
re-enabled.

tests/deferred_yield_higher/Makefile

@@ -0,0 +1,5 @@
+include ../Makefile.tests_common
+
+FEATURES_BLACKLIST += arch_avr8 arch_msp430 arch_riscv arch_mips32r2
+
+include $(RIOTBASE)/Makefile.include

tests/deferred_yield_higher/Makefile.ci

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+BOARD_INSUFFICIENT_MEMORY := \
+    nucleo-l011k4 \
+    #

tests/deferred_yield_higher/README.md

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+Introduction
+============
+
+This test verifies that a thread can call "thread_yield_higher()" with IRQs
+disabled, and that the actual context switch is deferred until IRQs are
+re-enabled.
+
+For the test to be successful, the printed messages must be in order, as follows:
+
+```
+1. post yield
+2. second thread scheduled
+3. post irq enable
+```

tests/deferred_yield_higher/main.c

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+/*
+ * Copyright (C) 2021 Inria
+ *               2021 Freie Universität Berlin
+ *               2021 Kaspar Schleiser <kaspar@schleiser.de>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup tests
+ * @{
+ *
+ * @file
+ * @brief   Application for testing thread_yield_higher() with IRQs disabled
+ *
+ * @author  Kaspar Schleiser <kaspar@schleiser.de>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include "irq.h"
+#include "thread.h"
+
+static char t2_stack[THREAD_STACKSIZE_DEFAULT];
+
+static void *second_thread(void *arg)
+{
+    puts("2. second thread scheduled");
+    return arg;
+}
+
+int main(void)
+{
+    thread_create(
+        t2_stack, sizeof(t2_stack),
+        THREAD_PRIORITY_MAIN - 1,
+        THREAD_CREATE_WOUT_YIELD | THREAD_CREATE_STACKTEST,
+        second_thread, NULL, "nr2");
+
+    irq_disable();
+    thread_yield_higher();
+    puts("1. post yield");
+    irq_enable();
+    puts("3. post irq enable");
+
+    puts("if above messages are in order, this test succeeded.");
+
+    return 0;
+}

tests/deferred_yield_higher/tests/test.py

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+#!/usr/bin/env python3
+
+# Copyright (C) 2017 Kaspar Schleiser <kaspar@schleiser.de>
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+import sys
+from testrunner import run
+
+
+def testfunc(child):
+    child.expect_exact('1. post yield')
+    child.expect_exact('2. second thread scheduled')
+    child.expect_exact('3. post irq enable')
+
+
+if __name__ == "__main__":
+    sys.exit(run(testfunc))