subsys/ztest: Revert "Make 1cpu tests run on CPU 0 specifically"

This change introduced some weird failures on x86 that will take some
time to untangle, and wasn't a particularly important feature to
merge.  Revert for now.

This reverts commit adc901a.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>

Author: Andy Ross

subsys/testsuite/ztest/src/ztest.c

@@ -97,28 +97,26 @@ static int cleanup_test(struct unit_test *test)
 #endif
 #define CPUHOLD_STACK_SZ (512 + CONFIG_TEST_EXTRA_STACK_SIZE)
 
-#if defined(CONFIG_SMP) && (CONFIG_MP_NUM_CPUS > 1)
-static struct k_thread cpuhold_threads[CONFIG_MP_NUM_CPUS];
-K_KERNEL_STACK_ARRAY_DEFINE(cpuhold_stacks, CONFIG_MP_NUM_CPUS, CPUHOLD_STACK_SZ);
+static struct k_thread cpuhold_threads[NUM_CPUHOLD];
+K_KERNEL_STACK_ARRAY_DEFINE(cpuhold_stacks, NUM_CPUHOLD, CPUHOLD_STACK_SZ);
 static struct k_sem cpuhold_sem;
-atomic_t cpuhold_holding;
 volatile int cpuhold_active;
-#endif
 
 /* "Holds" a CPU for use with the "1cpu" test cases.  Note that we
  * can't use tools like the cpumask feature because we have tests that
  * may need to control that configuration themselves.  We do this at
  * the lowest level, but locking interrupts directly and spinning.
  */
-static inline void cpu_hold(void *arg1, void *arg2, void *arg3)
+static void cpu_hold(void *arg1, void *arg2, void *arg3)
 {
 	ARG_UNUSED(arg1);
 	ARG_UNUSED(arg2);
 	ARG_UNUSED(arg3);
-#if defined(CONFIG_SMP) && (CONFIG_MP_NUM_CPUS > 1)
 	unsigned int key = arch_irq_lock();
 	uint32_t dt, start_ms = k_uptime_get_32();
 
+	k_sem_give(&cpuhold_sem);
+
 #if defined(CONFIG_ARM64) && defined(CONFIG_FPU_SHARING)
 	/*
 	 * We'll be spinning with IRQs disabled. The flush-your-FPU request
@@ -130,26 +128,6 @@ static inline void cpu_hold(void *arg1, void *arg2, void *arg3)
 	z_arm64_flush_local_fpu();
 #endif
 
-	/* One of these threads will end up on cpu 0.  Its job is to
-	 * wait for the others to start holding their CPUs, then wake
-	 * up the main test thread and exit, so that the test starts
-	 * running on cpu 0. Note that the spinning here is a
-	 * CPU-local loop, not k_busy_wait(), which tends to involve
-	 * the timer driver and cause performance weirdness in SMP
-	 * situations.
-	 */
-	if (arch_curr_cpu()->id == 0) {
-		while (atomic_get(&cpuhold_holding) < (CONFIG_MP_NUM_CPUS - 1)) {
-			for (volatile int i = 0; i < 10000; i++) {
-			}
-		}
-
-		k_sem_give(&cpuhold_sem);
-		arch_irq_unlock(key);
-		return;
-	}
-
-	atomic_inc(&cpuhold_holding);
 	while (cpuhold_active) {
 		k_busy_wait(1000);
 	}
@@ -163,23 +141,24 @@ static inline void cpu_hold(void *arg1, void *arg2, void *arg3)
 	zassert_true(dt < 3000,
 		     "1cpu test took too long (%d ms)", dt);
 	arch_irq_unlock(key);
-#endif
 }
 
 void z_impl_z_test_1cpu_start(void)
 {
-#if defined(CONFIG_SMP) && (CONFIG_MP_NUM_CPUS > 1)
+	cpuhold_active = 1;
 #ifdef CONFIG_THREAD_NAME
 	char tname[CONFIG_THREAD_MAX_NAME_LEN];
 #endif
-	cpuhold_active = 1;
 	k_sem_init(&cpuhold_sem, 0, 999);
-	atomic_set(&cpuhold_holding, 0);
 
-	/* Spawn threads to "hold" the other CPUs, waiting for each to
-	 * signal us that it's locked and spinning.
+	/* Spawn N-1 threads to "hold" the other CPUs, waiting for
+	 * each to signal us that it's locked and spinning.
+	 *
+	 * Note that NUM_CPUHOLD can be a value that causes coverity
+	 * to flag the following loop as DEADCODE so suppress the warning.
 	 */
-	for (int i = 0; i < CONFIG_MP_NUM_CPUS; i++)  {
+	/* coverity[DEADCODE] */
+	for (int i = 0; i < NUM_CPUHOLD; i++)  {
 		k_thread_create(&cpuhold_threads[i],
 				cpuhold_stacks[i], CPUHOLD_STACK_SZ,
 				(k_thread_entry_t) cpu_hold, NULL, NULL, NULL,
@@ -188,23 +167,21 @@ void z_impl_z_test_1cpu_start(void)
 		snprintk(tname, CONFIG_THREAD_MAX_NAME_LEN, "cpuhold%02d", i);
 		k_thread_name_set(&cpuhold_threads[i], tname);
 #endif
+		k_sem_take(&cpuhold_sem, K_FOREVER);
 	}
-
-	/* Sleep, waiting to be woken up on cpu0 */
-	k_sem_take(&cpuhold_sem, K_FOREVER);
-	__ASSERT(arch_curr_cpu()->id == 0, "1cpu case running on wrong cpu");
-#endif
 }
 
 void z_impl_z_test_1cpu_stop(void)
 {
-#if defined(CONFIG_SMP) && (CONFIG_MP_NUM_CPUS > 1)
 	cpuhold_active = 0;
 
-	for (int i = 0; i < CONFIG_MP_NUM_CPUS; i++)  {
+	/* Note that NUM_CPUHOLD can be a value that causes coverity
+	 * to flag the following loop as DEADCODE so suppress the warning.
+	 */
+	/* coverity[DEADCODE] */
+	for (int i = 0; i < NUM_CPUHOLD; i++)  {
 		k_thread_abort(&cpuhold_threads[i]);
 	}
-#endif
 }
 
 #ifdef CONFIG_USERSPACE