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root/jsr166/jsr166/src/jsr166y/ForkJoinPool.java

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.167 by jsr166, Sun Dec 30 02:05:53 2012 UTC vs.
Revision 1.189 by jsr166, Sat Sep 12 19:16:45 2015 UTC

#	Line 440 | Line 440 | public class ForkJoinPool extends Abstra
440		* Common Pool
441		* ===========
442		*
443	<	* The static commonPool always exists after static
443	>	* The static common Pool always exists after static
444		* initialization.  Since it (or any other created pool) need
445		* never be used, we minimize initial construction overhead and
446		* footprint to the setup of about a dozen fields, with no nested
#	Line 687 | Line 687 | public class ForkJoinPool extends Abstra
687		return (n >= 0) ? 0 : -n; // ignore transient negative
688		}
689
690	<	/**
690	>	/**
691		* Provides a more accurate estimate of whether this queue has
692		* any tasks than does queueSize, by checking whether a
693		* near-empty queue has at least one unclaimed task.
#	Line 708 | Line 708 | public class ForkJoinPool extends Abstra
708		* shared-queue version is embedded in method externalPush.)
709		*
710		* @param task the task. Caller must ensure non-null.
711	<	* @throw RejectedExecutionException if array cannot be resized
711	>	* @throws RejectedExecutionException if array cannot be resized
712		*/
713		final void push(ForkJoinTask<?> task) {
714		ForkJoinTask<?>[] a; ForkJoinPool p;
#	Line 725 | Line 725 | public class ForkJoinPool extends Abstra
725		}
726		}
727
728	<	/**
728	>	/**
729		* Initializes or doubles the capacity of array. Call either
730		* by owner or with lock held -- it is OK for base, but not
731		* top, to move while resizings are in progress.
#	Line 907 | Line 907 | public class ForkJoinPool extends Abstra
907		* or any other cancelled task. Returns (true) on any CAS
908		* or consistency check failure so caller can retry.
909		*
910	<	* @return false if no progress can be made, else true;
910	>	* @return false if no progress can be made, else true
911		*/
912		final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
913		boolean stat = true, removed = false, empty = true;
#	Line 952 | Line 952 | public class ForkJoinPool extends Abstra
952
953		/**
954		* Polls for and executes the given task or any other task in
955	<	* its CountedCompleter computation
955	>	* its CountedCompleter computation.
956		*/
957		final boolean pollAndExecCC(ForkJoinTask<?> root) {
958		ForkJoinTask<?>[] a; int b; Object o;
#	Line 1026 | Line 1026 | public class ForkJoinPool extends Abstra
1026		private static final int ABASE;
1027		private static final int ASHIFT;
1028		static {
1029	–	int s;
1029		try {
1030		U = getUnsafe();
1031		Class<?> k = WorkQueue.class;
#	Line 1034 | Line 1033 | public class ForkJoinPool extends Abstra
1033		QLOCK = U.objectFieldOffset
1034		(k.getDeclaredField("qlock"));
1035		ABASE = U.arrayBaseOffset(ak);
1036	<	s = U.arrayIndexScale(ak);
1036	>	int scale = U.arrayIndexScale(ak);
1037	>	if ((scale & (scale - 1)) != 0)
1038	>	throw new Error("data type scale not a power of two");
1039	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
1040		} catch (Exception e) {
1041		throw new Error(e);
1042		}
1041	–	if ((s & (s-1)) != 0)
1042	–	throw new Error("data type scale not a power of two");
1043	–	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1043		}
1044		}
1045
#	Line 1074 | Line 1073 | public class ForkJoinPool extends Abstra
1073		* to paranoically avoid potential initialization circularities
1074		* as well as to simplify generated code.
1075		*/
1076	<	static final ForkJoinPool commonPool;
1076	>	static final ForkJoinPool common;
1077
1078		/**
1079	<	* Common pool parallelism. Must equal commonPool.parallelism.
1079	>	* Common pool parallelism. Must equal common.parallelism.
1080		*/
1081	<	static final int commonPoolParallelism;
1081	>	static final int commonParallelism;
1082
1083		/**
1084		* Sequence number for creating workerNamePrefix.
#	Line 1132 | Line 1131 | public class ForkJoinPool extends Abstra
1131		*/
1132		private static final int SEED_INCREMENT = 0x61c88647;
1133
1134	<	/**
1134	>	/*
1135		* Bits and masks for control variables
1136		*
1137		* Field ctl is a long packed with:
#	Line 1245 | Line 1244 | public class ForkJoinPool extends Abstra
1244		volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
1245		volatile Object pad18, pad19, pad1a, pad1b;
1246
1247	<	/*
1247	>	/**
1248		* Acquires the plock lock to protect worker array and related
1249		* updates. This method is called only if an initial CAS on plock
1250	<	* fails. This acts as a spinLock for normal cases, but falls back
1250	>	* fails. This acts as a spinlock for normal cases, but falls back
1251		* to builtin monitor to block when (rarely) needed. This would be
1252		* a terrible idea for a highly contended lock, but works fine as
1253		* a more conservative alternative to a pure spinlock.
#	Line 1522 | Line 1521 | public class ForkJoinPool extends Abstra
1521		(m = ws.length - 1) < 0) { // initialize workQueues
1522		int p = config & SMASK;         // find power of two table size
1523		int n = (p > 1) ? p - 1 : 1;    // ensure at least 2 slots
1524	<	n |= n >>> 1; n |= n >>> 2;  n |= n >>> 4;
1525	<	n |= n >>> 8; n |= n >>> 16; n = (n + 1) << 1;
1524	>	n |= n >>> 1;
1525	>	n |= n >>> 2;
1526	>	n |= n >>> 4;
1527	>	n |= n >>> 8;
1528	>	n |= n >>> 16;
1529	>	n = (n + 1) << 1;
1530		WorkQueue[] nws = ((ws = workQueues) == null || ws.length == 0 ?
1531		new WorkQueue[n] : null);
1532		if (((ps = plock) & PL_LOCK) != 0 ||
#	Line 1932 | Line 1935 | public class ForkJoinPool extends Abstra
1935		* @param task the task to join
1936		* @param mode if shared, exit upon completing any task
1937		* if all workers are active
1935	–	*
1938		*/
1939		private int helpComplete(ForkJoinTask<?> task, int mode) {
1940		WorkQueue[] ws; WorkQueue q; int m, n, s, u;
#	Line 2129 | Line 2131 | public class ForkJoinPool extends Abstra
2131		w.runSubtask(t);
2132		}
2133		}
2134	<	else if (active) {       // decrement active count without queuing
2134	>	else if (active) {      // decrement active count without queuing
2135		long nc = (c = ctl) - AC_UNIT;
2136		if ((int)(nc >> AC_SHIFT) + (config & SMASK) == 0)
2137	<	return;          // bypass decrement-then-increment
2137	>	return;         // bypass decrement-then-increment
2138		if (U.compareAndSwapLong(this, CTL, c, nc))
2139		active = false;
2140		}
#	Line 2187 | Line 2189 | public class ForkJoinPool extends Abstra
2189		* producing extra tasks amortizes the uncertainty of progress and
2190		* diffusion assumptions.
2191		*
2192	<	* So, users will want to use values larger, but not much larger
2192	>	* So, users will want to use values larger (but not much larger)
2193		* than 1 to both smooth over transient shortages and hedge
2194		* against uneven progress; as traded off against the cost of
2195		* extra task overhead. We leave the user to pick a threshold
#	Line 2241 | Line 2243 | public class ForkJoinPool extends Abstra
2243		*/
2244		private boolean tryTerminate(boolean now, boolean enable) {
2245		int ps;
2246	<	if (this == commonPool)                    // cannot shut down
2246	>	if (this == common)                    // cannot shut down
2247		return false;
2248		if ((ps = plock) >= 0) {                   // enable by setting plock
2249		if (!enable)
#	Line 2332 | Line 2334 | public class ForkJoinPool extends Abstra
2334		static WorkQueue commonSubmitterQueue() {
2335		ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2336		return ((z = submitters.get()) != null &&
2337	<	(p = commonPool) != null &&
2337	>	(p = common) != null &&
2338		(ws = p.workQueues) != null &&
2339		(m = ws.length - 1) >= 0) ?
2340		ws[m & z.seed & SQMASK] : null;
#	Line 2346 | Line 2348 | public class ForkJoinPool extends Abstra
2348		ForkJoinTask<?>[] a;  int m, s;
2349		if (t != null &&
2350		(z = submitters.get()) != null &&
2351	<	(p = commonPool) != null &&
2351	>	(p = common) != null &&
2352		(ws = p.workQueues) != null &&
2353		(m = ws.length - 1) >= 0 &&
2354		(q = ws[m & z.seed & SQMASK]) != null &&
#	Line 2423 | Line 2425 | public class ForkJoinPool extends Abstra
2425		ForkJoinTask<?>[] a;  int m, s, n;
2426		if (t != null &&
2427		(z = submitters.get()) != null &&
2428	<	(p = commonPool) != null &&
2428	>	(p = common) != null &&
2429		(ws = p.workQueues) != null &&
2430		(m = ws.length - 1) >= 0 &&
2431		(q = ws[m & z.seed & SQMASK]) != null &&
#	Line 2452 | Line 2454 | public class ForkJoinPool extends Abstra
2454		}
2455		}
2456
2455	–	/**
2456	–	* Restricted version of helpQuiescePool for external callers
2457	–	*/
2458	–	static void externalHelpQuiescePool() {
2459	–	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2460	–	if ((p = commonPool) != null &&
2461	–	(q = p.findNonEmptyStealQueue(1)) != null &&
2462	–	(b = q.base) - q.top < 0 &&
2463	–	(t = q.pollAt(b)) != null) {
2464	–	if (q.base - q.top < 0)
2465	–	p.signalWork(q);
2466	–	t.doExec();
2467	–	}
2468	–	}
2469	–
2457		// Exported methods
2458
2459		// Constructors
#	Line 2483 | Line 2470 | public class ForkJoinPool extends Abstra
2470		*         java.lang.RuntimePermission}{@code ("modifyThread")}
2471		*/
2472		public ForkJoinPool() {
2473	<	this(Runtime.getRuntime().availableProcessors(),
2473	>	this(Math.min(MAX_CAP, Runtime.getRuntime().availableProcessors()),
2474		defaultForkJoinWorkerThreadFactory, null, false);
2475		}
2476
#	Line 2566 | Line 2553 | public class ForkJoinPool extends Abstra
2553
2554		/**
2555		* Returns the common pool instance. This pool is statically
2556	<	* constructed; its run state is unaffected by attempts to
2557	<	* {@link #shutdown} or {@link #shutdownNow}.
2556	>	* constructed; its run state is unaffected by attempts to {@link
2557	>	* #shutdown} or {@link #shutdownNow}. However this pool and any
2558	>	* ongoing processing are automatically terminated upon program
2559	>	* {@link System#exit}.  Any program that relies on asynchronous
2560	>	* task processing to complete before program termination should
2561	>	* invoke {@code commonPool().}{@link #awaitQuiescence}, before
2562	>	* exit.
2563		*
2564		* @return the common pool instance
2565	+	* @since 1.8
2566		*/
2567		public static ForkJoinPool commonPool() {
2568	<	// assert commonPool != null : "static init error";
2569	<	return commonPool;
2568	>	// assert common != null : "static init error";
2569	>	return common;
2570		}
2571
2572		// Execution methods
#	Line 2696 | Line 2689 | public class ForkJoinPool extends Abstra
2689		// In previous versions of this class, this method constructed
2690		// a task to run ForkJoinTask.invokeAll, but now external
2691		// invocation of multiple tasks is at least as efficient.
2692	<	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2700	<	// Workaround needed because method wasn't declared with
2701	<	// wildcards in return type but should have been.
2702	<	@SuppressWarnings({"unchecked", "rawtypes"})
2703	<	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2692	>	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
2693
2694		boolean done = false;
2695		try {
2696		for (Callable<T> t : tasks) {
2697		ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2698	+	futures.add(f);
2699		externalPush(f);
2710	–	fs.add(f);
2700		}
2701	<	for (ForkJoinTask<T> f : fs)
2702	<	f.quietlyJoin();
2701	>	for (int i = 0, size = futures.size(); i < size; i++)
2702	>	((ForkJoinTask<?>)futures.get(i)).quietlyJoin();
2703		done = true;
2704		return futures;
2705		} finally {
2706		if (!done)
2707	<	for (ForkJoinTask<T> f : fs)
2708	<	f.cancel(false);
2707	>	for (int i = 0, size = futures.size(); i < size; i++)
2708	>	futures.get(i).cancel(false);
2709		}
2710		}
2711
#	Line 2752 | Line 2741 | public class ForkJoinPool extends Abstra
2741		* Returns the targeted parallelism level of the common pool.
2742		*
2743		* @return the targeted parallelism level of the common pool
2744	+	* @since 1.8
2745		*/
2746		public static int getCommonPoolParallelism() {
2747	<	return commonPoolParallelism;
2747	>	return commonParallelism;
2748		}
2749
2750		/**
#	Line 3012 | Line 3002 | public class ForkJoinPool extends Abstra
3002		* Possibly initiates an orderly shutdown in which previously
3003		* submitted tasks are executed, but no new tasks will be
3004		* accepted. Invocation has no effect on execution state if this
3005	<	* is the {@link #commonPool}, and no additional effect if
3005	>	* is the {@link #commonPool()}, and no additional effect if
3006		* already shut down.  Tasks that are in the process of being
3007		* submitted concurrently during the course of this method may or
3008		* may not be rejected.
#	Line 3030 | Line 3020 | public class ForkJoinPool extends Abstra
3020		/**
3021		* Possibly attempts to cancel and/or stop all tasks, and reject
3022		* all subsequently submitted tasks.  Invocation has no effect on
3023	<	* execution state if this is the {@link #commonPool}, and no
3023	>	* execution state if this is the {@link #commonPool()}, and no
3024		* additional effect if already shut down. Otherwise, tasks that
3025		* are in the process of being submitted or executed concurrently
3026		* during the course of this method may or may not be
#	Line 3093 | Line 3083 | public class ForkJoinPool extends Abstra
3083		/**
3084		* Blocks until all tasks have completed execution after a
3085		* shutdown request, or the timeout occurs, or the current thread
3086	<	* is interrupted, whichever happens first. Note that the {@link
3087	<	* #commonPool()} never terminates until program shutdown so
3088	<	* this method will always time out.
3086	>	* is interrupted, whichever happens first. Because the {@link
3087	>	* #commonPool()} never terminates until program shutdown, when
3088	>	* applied to the common pool, this method is equivalent to {@link
3089	>	* #awaitQuiescence} but always returns {@code false}.
3090		*
3091		* @param timeout the maximum time to wait
3092		* @param unit the time unit of the timeout argument
#	Line 3105 | Line 3096 | public class ForkJoinPool extends Abstra
3096		*/
3097		public boolean awaitTermination(long timeout, TimeUnit unit)
3098		throws InterruptedException {
3099	+	if (Thread.interrupted())
3100	+	throw new InterruptedException();
3101	+	if (this == common) {
3102	+	awaitQuiescence(timeout, unit);
3103	+	return false;
3104	+	}
3105		long nanos = unit.toNanos(timeout);
3106		if (isTerminated())
3107		return true;
#	Line 3124 | Line 3121 | public class ForkJoinPool extends Abstra
3121		}
3122
3123		/**
3124	+	* If called by a ForkJoinTask operating in this pool, equivalent
3125	+	* in effect to {@link ForkJoinTask#helpQuiesce}. Otherwise,
3126	+	* waits and/or attempts to assist performing tasks until this
3127	+	* pool {@link #isQuiescent} or the indicated timeout elapses.
3128	+	*
3129	+	* @param timeout the maximum time to wait
3130	+	* @param unit the time unit of the timeout argument
3131	+	* @return {@code true} if quiescent; {@code false} if the
3132	+	* timeout elapsed.
3133	+	*/
3134	+	public boolean awaitQuiescence(long timeout, TimeUnit unit) {
3135	+	long nanos = unit.toNanos(timeout);
3136	+	ForkJoinWorkerThread wt;
3137	+	Thread thread = Thread.currentThread();
3138	+	if ((thread instanceof ForkJoinWorkerThread) &&
3139	+	(wt = (ForkJoinWorkerThread)thread).pool == this) {
3140	+	helpQuiescePool(wt.workQueue);
3141	+	return true;
3142	+	}
3143	+	long startTime = System.nanoTime();
3144	+	WorkQueue[] ws;
3145	+	int r = 0, m;
3146	+	boolean found = true;
3147	+	while (!isQuiescent() && (ws = workQueues) != null &&
3148	+	(m = ws.length - 1) >= 0) {
3149	+	if (!found) {
3150	+	if ((System.nanoTime() - startTime) > nanos)
3151	+	return false;
3152	+	Thread.yield(); // cannot block
3153	+	}
3154	+	found = false;
3155	+	for (int j = (m + 1) << 2; j >= 0; --j) {
3156	+	ForkJoinTask<?> t; WorkQueue q; int b;
3157	+	if ((q = ws[r++ & m]) != null && (b = q.base) - q.top < 0) {
3158	+	found = true;
3159	+	if ((t = q.pollAt(b)) != null) {
3160	+	if (q.base - q.top < 0)
3161	+	signalWork(q);
3162	+	t.doExec();
3163	+	}
3164	+	break;
3165	+	}
3166	+	}
3167	+	}
3168	+	return true;
3169	+	}
3170	+
3171	+	/**
3172	+	* Waits and/or attempts to assist performing tasks indefinitely
3173	+	* until the {@link #commonPool()} {@link #isQuiescent}.
3174	+	*/
3175	+	static void quiesceCommonPool() {
3176	+	common.awaitQuiescence(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
3177	+	}
3178	+
3179	+	/**
3180		* Interface for extending managed parallelism for tasks running
3181		* in {@link ForkJoinPool}s.
3182		*
#	Line 3276 | Line 3329 | public class ForkJoinPool extends Abstra
3329		private static final long QLOCK;
3330
3331		static {
3332	<	int s; // initialize field offsets for CAS etc
3332	>	// initialize field offsets for CAS etc
3333		try {
3334		U = getUnsafe();
3335		Class<?> k = ForkJoinPool.class;
#	Line 3296 | Line 3349 | public class ForkJoinPool extends Abstra
3349		(wk.getDeclaredField("qlock"));
3350		Class<?> ak = ForkJoinTask[].class;
3351		ABASE = U.arrayBaseOffset(ak);
3352	<	s = U.arrayIndexScale(ak);
3353	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3352	>	int scale = U.arrayIndexScale(ak);
3353	>	if ((scale & (scale - 1)) != 0)
3354	>	throw new Error("data type scale not a power of two");
3355	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
3356		} catch (Exception e) {
3357		throw new Error(e);
3358		}
3304	–	if ((s & (s-1)) != 0)
3305	–	throw new Error("data type scale not a power of two");
3359
3360		submitters = new ThreadLocal<Submitter>();
3361		ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
#	Line 3339 | Line 3392 | public class ForkJoinPool extends Abstra
3392		par = Runtime.getRuntime().availableProcessors();
3393		if (par > MAX_CAP)
3394		par = MAX_CAP;
3395	<	commonPoolParallelism = par;
3395	>	commonParallelism = par;
3396		long np = (long)(-par); // precompute initial ctl value
3397		long ct = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
3398
3399	<	commonPool = new ForkJoinPool(par, ct, fac, handler);
3399	>	common = new ForkJoinPool(par, ct, fac, handler);
3400		}
3401
3349	–
3402		/**
3403		* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
3404		* Replace with a simple call to Unsafe.getUnsafe when integrating
#	Line 3357 | Line 3409 | public class ForkJoinPool extends Abstra
3409		private static sun.misc.Unsafe getUnsafe() {
3410		try {
3411		return sun.misc.Unsafe.getUnsafe();
3412	<	} catch (SecurityException se) {
3413	<	try {
3414	<	return java.security.AccessController.doPrivileged
3415	<	(new java.security
3416	<	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
3417	<	public sun.misc.Unsafe run() throws Exception {
3418	<	java.lang.reflect.Field f = sun.misc
3419	<	.Unsafe.class.getDeclaredField("theUnsafe");
3420	<	f.setAccessible(true);
3421	<	return (sun.misc.Unsafe) f.get(null);
3422	<	}});
3423	<	} catch (java.security.PrivilegedActionException e) {
3424	<	throw new RuntimeException("Could not initialize intrinsics",
3425	<	e.getCause());
3426	<	}
3412	>	} catch (SecurityException tryReflectionInstead) {}
3413	>	try {
3414	>	return java.security.AccessController.doPrivileged
3415	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
3416	>	public sun.misc.Unsafe run() throws Exception {
3417	>	Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
3418	>	for (java.lang.reflect.Field f : k.getDeclaredFields()) {
3419	>	f.setAccessible(true);
3420	>	Object x = f.get(null);
3421	>	if (k.isInstance(x))
3422	>	return k.cast(x);
3423	>	}
3424	>	throw new NoSuchFieldError("the Unsafe");
3425	>	}});
3426	>	} catch (java.security.PrivilegedActionException e) {
3427	>	throw new RuntimeException("Could not initialize intrinsics",
3428	>	e.getCause());
3429		}
3430		}
3377	–
3431		}

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