kernel: Relax cpu_ent::interrupt_time locking

The value isn't accessed by the other CPUs and all writes and reads are
done with interrupts disabled.

src/system/kernel/int.cpp

@@ -359,14 +359,16 @@ int_io_interrupt_handler(int vector, bool levelTriggered)
 	if (!sVectors[vector].no_lock_vector)
 		release_spinlock(&sVectors[vector].vector_lock);
 
-	SpinLocker locker(sVectors[vector].load_lock);
+	SpinLocker vectorLocker(sVectors[vector].load_lock);
 	bigtime_t deltaTime = system_time() - start;
 	sVectors[vector].last_measure_active += deltaTime;
-	locker.Unlock();
+	vectorLocker.Unlock();
 
-	atomic_add64(&get_cpu_struct()->interrupt_time, deltaTime);
+	cpu_ent* cpu = get_cpu_struct();
+	cpu->interrupt_time += deltaTime;
 	if (sVectors[vector].type == INTERRUPT_TYPE_IRQ)
-		atomic_add64(&get_cpu_struct()->irq_time, deltaTime);
+		cpu->irq_time += deltaTime;
+
 	update_int_load(vector);
 
 	if (levelTriggered)

src/system/kernel/scheduler/scheduler.cpp

@@ -393,8 +393,7 @@ reschedule(int32 nextState)
 	ThreadData* oldThreadData = oldThread->scheduler_data;
 
 	// return time spent in interrupts
-	oldThreadData->IncreaseStolenTime(
-		gCPU[thisCPU].interrupt_time - oldThreadData->LastInterruptTime());
+	oldThreadData->SetStolenInterruptTime(gCPU[thisCPU].interrupt_time);
 
 	bool enqueueOldThread = false;
 	bool putOldThreadAtBack = false;

src/system/kernel/scheduler/scheduler_thread.cpp

@@ -166,13 +166,6 @@ ThreadData::ComputeLoad()
 	SCHEDULER_ENTER_FUNCTION();
 
 	ASSERT(gTrackLoad);
-
-	if (fLastInterruptTime > 0) {
-		bigtime_t interruptTime = gCPU[smp_get_current_cpu()].interrupt_time;
-		interruptTime -= fLastInterruptTime;
-		fMeasureActiveTime -= interruptTime;
-	}
-
 	compute_load(fMeasureTime, fMeasureActiveTime, fLoad);
 }
 

src/system/kernel/scheduler/scheduler_thread.h

@@ -51,12 +51,9 @@ public:
 			bool		ChooseCoreAndCPU(CoreEntry*& targetCore,
 							CPUEntry*& targetCPU);
 
-	inline	bigtime_t	LastInterruptTime() const
-							{ return fLastInterruptTime; }
 	inline	void		SetLastInterruptTime(bigtime_t interruptTime)
 							{ fLastInterruptTime = interruptTime; }
-
-	inline	void		IncreaseStolenTime(bigtime_t stolenTime);
+	inline	void		SetStolenInterruptTime(bigtime_t interruptTime);
 
 	inline	void		GoesAway();
 	inline	bigtime_t	WentSleep() const	{ return fWentSleep; }
@@ -226,10 +223,13 @@ ThreadData::ShouldCancelPenalty() const
 
 
 inline void
-ThreadData::IncreaseStolenTime(bigtime_t stolenTime)
+ThreadData::SetStolenInterruptTime(bigtime_t interruptTime)
 {
 	SCHEDULER_ENTER_FUNCTION();
-	fStolenTime += stolenTime;
+
+	interruptTime -= fLastInterruptTime;
+	fStolenTime += interruptTime;
+	fMeasureActiveTime -= interruptTime;
 }