tests/kernel/mem_protect/sys_sem: qemu_x86_64 intermittent failure

[pabigot]

This sometimes shows up in buildkite, e.g. https://buildkite.com/zephyr/zephyr/builds/9752

It can be reproduced on master with:

sanitycheck -p qemu_x86_64 -s tests/kernel/mem_protect/sys_sem/kernel.memory_protection.sys_sem

When the failure occurs the output is:

SeaBIOS (version rel-1.12.1-0-ga5cab58-dirty-20200625_115407-9426dddc0a1f-zephyr)
Booting from ROM..*** Booting Zephyr OS build zephyr-v2.4.0-207-gc02eb30bbfbe  ***
Running test suite test_sys_sem
===================================================================
START - test_basic_sem_test
 PASS - test_basic_sem_test
===================================================================
START - test_simple_sem_from_isr
 PASS - test_simple_sem_from_isr
===================================================================
START - test_sem_take_timeout_isr
 PASS - test_sem_take_timeout_isr
===================================================================
START - test_sem_give_take_from_isr
 PASS - test_sem_give_take_from_isr
===================================================================
START - test_simple_sem_from_task
 PASS - test_simple_sem_from_task
===================================================================
START - test_sem_take_no_wait
 PASS - test_sem_take_no_wait
===================================================================
START - test_sem_take_no_wait_fails
 PASS - test_sem_take_no_wait_fails
===================================================================
START - test_sem_take_timeout_fails
 PASS - test_sem_take_timeout_fails
===================================================================
START - test_sem_take_timeout

    Assertion failed at WEST_TOPDIR/zephyr/tests/kernel/mem_protect/sys_sem/src/main.c:277: test_sem_take_timeout: (ret_value == 0 is false)
sys_sem_take failed when its shouldn't have
 FAIL - test_sem_take_timeout
===================================================================
START - test_sem_take_timeout_forever
 PASS - test_sem_take_timeout_forever
===================================================================
START - test_sem_take_multiple
 PASS - test_sem_take_multiple
===================================================================
START - test_sem_give_limit
 PASS - test_sem_give_limit
===================================================================
START - test_sem_multiple_threads_wait
 PASS - test_sem_multiple_threads_wait
===================================================================
Test suite test_sys_sem failed.
===================================================================
PROJECT EXECUTION FAILED

[andrewboie]

there's nothing we can do about this, qemu_x86_64 doesn't implement icount if multiple CPUs are enabled and you will occasionally get timing sensitive tests to fail.