tests: kernel: context: Bugfix for POSIX arch in TICKLESS

In the POSIX architecture, with the inf_clock "SOC", time does
not pass while the CPU is running. Tests that require time to pass
while busy waiting should call k_busy_wait() or in some other way
set the CPU to idle. This test was setting the CPU to idle while
waiting for the next time slice. This is ok if the system tick
(timer) is active and awaking the CPU every system tick period.
But when configured in tickless mode that is not the case, and the
CPU was set to sleep for an indefinite amount of time.
This commit fixes it by using k_busy_wait(a few microseconds) inside
that busy wait loop instead.

Signed-off-by: Alberto Escolar Piedras <[email protected]>

Author: aescolar

tests/kernel/context/src/main.c

@@ -244,7 +244,7 @@ static void _test_kernel_cpu_idle(int atomic)
 	tms = k_uptime_get_32();
 	while (tms == k_uptime_get_32()) {
 #if defined(CONFIG_ARCH_POSIX)
-		posix_halt_cpu(); /*Sleep until next IRQ*/
+		k_busy_wait(50);
 #endif
 	}