kernel: fix race condition on boot, using SetBitAtomic

fix #18915

Change-Id: Ia8829822e21f6d6b765746ddab05f8781385745f
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7777
Haiku-Format: Haiku-format Bot <[email protected]>
Reviewed-by: Fredrik Holmqvist <[email protected]>
Reviewed-by: Jérôme Duval <[email protected]>
Tested-by: Commit checker robot <[email protected]>

src/system/kernel/cpu.cpp

@@ -150,7 +150,7 @@ cpu_preboot_init_percpu(kernel_args *args, int curr_cpu)
 	// we can use it for get_current_cpu
 	memset(&gCPU[curr_cpu], 0, sizeof(gCPU[curr_cpu]));
 	gCPU[curr_cpu].cpu_num = curr_cpu;
-	gCPUEnabled.SetBit(curr_cpu);
+	gCPUEnabled.SetBitAtomic(curr_cpu);
 
 	list_init(&gCPU[curr_cpu].irqs);
 	B_INITIALIZE_SPINLOCK(&gCPU[curr_cpu].irqs_lock);

src/system/kernel/scheduler/scheduler.cpp

@@ -379,7 +379,7 @@ reschedule(int32 nextState)
 
 	// select thread with the biggest priority and enqueue back the old thread
 	ThreadData* nextThreadData;
-	if (gCPU[thisCPU].disabled) {
+	if (!gCPUEnabled.GetBit(thisCPU)) {
 		if (!oldThreadData->IsIdle()) {
 			if (oldThread->pinned_to_cpu == 0) {
 				putOldThreadAtBack = true;