scheduler: Use sequential locks instead of atomic 64 bit access

headers/os/drivers/KernelExport.h

@@ -59,9 +59,9 @@ typedef struct {
 } seqlock;
 
 #define B_SEQLOCK_INITIALIZER	{ B_SPINLOCK_INITIALIZER, 0 }
-#define B_INITIALIZE_SEQLOCK(seqlock)	do {	\
-		B_INITIALIZE_SPINLOCK((seqlock)->lock);	\
-		(seqlock)->count = 0;					\
+#define B_INITIALIZE_SEQLOCK(seqlock)	do {		\
+		B_INITIALIZE_SPINLOCK(&(seqlock)->lock);	\
+		(seqlock)->count = 0;						\
 	} while (false)
 
 /* interrupt handling support for device drivers */

src/system/kernel/scheduler/low_latency.cpp

@@ -35,8 +35,16 @@ has_cache_expired(const ThreadData* threadData)
 {
 	ASSERT(!gSingleCore);
 
-	return atomic_get64(&threadData->GetCore()->fActiveTime)
-			- threadData->fWentSleepActive > kCacheExpire;
+	CoreEntry* core = threadData->GetCore();
+
+	bigtime_t activeTime;
+	uint32 count;
+	do {
+		count = acquire_read_seqlock(&core->fActiveTimeLock);
+		activeTime = core->fActiveTime;
+	} while (!release_read_seqlock(&core->fActiveTimeLock, count));
+
+	return activeTime - threadData->fWentSleepActive > kCacheExpire;
 }
 
 

src/system/kernel/scheduler/scheduler_cpu.cpp

@@ -272,6 +272,7 @@ CoreEntry::CoreEntry()
 {
 	B_INITIALIZE_SPINLOCK(&fCPULock);
 	B_INITIALIZE_SPINLOCK(&fQueueLock);
+	B_INITIALIZE_SEQLOCK(&fActiveTimeLock);
 }
 
 

src/system/kernel/scheduler/scheduler_cpu.h

@@ -100,6 +100,7 @@ struct CoreEntry : public MinMaxHeapLinkImpl<CoreEntry, int32>,
 						spinlock		fQueueLock;
 
 						bigtime_t		fActiveTime;
+						seqlock			fActiveTimeLock;
 
 						int32			fLoad;
 						bool			fHighLoad;

src/system/kernel/scheduler/scheduler_thread.h

@@ -177,8 +177,13 @@ ThreadData::GoesAway()
 	fLastInterruptTime = 0;
 
 	fWentSleep = system_time();
-	fWentSleepActive = atomic_get64(&fCore->fActiveTime);
 	fWentSleepCount = atomic_get(&fCore->fStarvationCounter);
+
+	uint32 count;
+	do {
+		count = acquire_read_seqlock(&fCore->fActiveTimeLock);
+		fWentSleepActive = fCore->fActiveTime;
+	} while (!release_read_seqlock(&fCore->fActiveTimeLock, count));
 }
 
 
@@ -262,7 +267,10 @@ ThreadData::UpdateActivity(bigtime_t active)
 {
 	fMeasureActiveTime += active;
 	gCPUEntries[smp_get_current_cpu()].fMeasureActiveTime += active;
-	atomic_add64(&fCore->fActiveTime, active);
+
+	WriteSequentialLocker locker(fCore->fActiveTimeLock);
+	fCore->fActiveTime += active;
+	locker.Unlock();
 }