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- 閿佺殑鐘舵€佸彉閲忔満鍒讹細 涓昏閿佺殑鐘舵€佽缃紝鏄惁鍏变韩鐘舵€佸彉閲忥紵
- 閿佺殑闃熷垪灏佽瀹氫箟锛氫富瑕佹槸鎸囩瓑寰呴槦鍒楀拰鏉′欢闃熷垪锛屾槸鍚﹂渶瑕佹潯浠堕槦鍒楁垨鑰呯瓑寰呴槦鍒楀畾涔夛紵
- 閿佺殑搴曞眰瀹炵幇鎿嶄綔锛?涓昏鏄寚搴曞眰CL閿佸拰CAS鎿嶄綔锛屾槸鍚﹂渶瑕佽€冭檻鑷棆閿佹垨鑰匔AS鎿嶄綔瀹炰緥瀵硅薄鏂规硶锛?/li>
- 閿佺殑缁勫悎瀹炵幇鏂伴攣锛?涓昏鏄熀浜庣嫭鍗犻攣鍜屽叡浜攣锛屾槸鍚﹁€冭檻瀵瑰簲API鑷畾涔夋搷浣滃疄鐜帮紵
缁间笂鎵€杩帮紝澶ц嚧鍙互鏍规嵁涓婅堪杩欎簺鏂瑰悜锛屾垜浠究鍙互娓呮馃墣锔忕煡閬揓ava棰嗗煙涓悇绉嶉攣瀹炵幇鐨勫熀鏈悊璁烘椂鍜屽疄鐜版€濇兂銆?/p>
鍏?CountDownLatch(闂攣)鐨勮璁′笌瀹炵幇
鍦↗ava棰嗗煙涓紝CountDownLatch(闂攣)鏄拡瀵逛簬Java澶氱嚎绋嬪苟鍙戞帶鍒朵腑鍊掕鏁板櫒鐨勫叿浣撴暟閲忥紝涓昏鏄噰鐢ㄩ€掑噺璁℃暟鏂瑰紡鐨勫€掕鏁板櫒鎬濇兂鍜屽熀浜嶢QS鍩虹鍚屾鍣ㄦ潵瀹炵幇鐨勪竴绉嶅悓姝ュ櫒宸ュ叿绫汇€?/p>
CountDownLatch(闂攣)鏄疛ava澶氱嚎绋嬪苟鍙戜腑鏈€甯歌鐨勪竴绉嶅悓姝ュ櫒锛屼粠閿佺殑鎬ц川涓婃潵鐪嬶紝灞炰簬鍏变韩閿侊紝鍏跺姛鑳界浉褰撲簬涓€涓绾跨▼鐜涓嬬殑鍊掓暟闂ㄩ棭銆?lt;br />CountDownLatch閫氳繃瀹氫箟涓€涓€掕鏁板櫒锛屽湪骞跺彂鐜涓嬬敱绾跨▼杩涜閫掑噺1鎿嶄綔锛屽綋璁℃暟鍊煎彉涓?涔嬪悗锛岃await鏂规硶闃诲鐨勭嚎绋嬪皢浼氬敜閱掋€?lt;br />閫氳繃CountDownLatch鍙互瀹炵幇绾跨▼闂寸殑璁℃暟鍚屾銆?/p>
1. 璁捐鎬濇兂
涓€鑸潵璇达紝閫氳繃瀹氫箟涓€涓€掕鏁板櫒锛屼负浜嗚鏌愪釜绾跨▼鎴栬€呭涓嚎绋嬪湪鏌愪釜杩愯鑺傜偣涓婄瓑寰匩涓潯浠堕兘婊¤冻鍚庯紝鎵嶈鎵€鏈夌殑绾跨▼缁х画寰€涓嬫墽琛岋紝鍏朵腑鍊掕鏁板櫒鐨勬暟閲忓垯涓篘锛屾瘡婊¤冻涓€涓潯浠讹紝鍊掕鏁板櫒灏变緷娆￠€愭笎閫掑噺1锛岀洿鍒癗-1=0鐨勬椂锛屾墍鏈夌瓑寰呯殑绾跨▼鎵嶅線涓嬬户缁墽琛屻€?lt;br />CountDownLatch绫绘渶鏃╂槸鍦↗DK1.5鐗堟湰鎻愪緵鐨勶紝浠庤璁℃€濇兂涓婃潵鐪嬶紝涓昏鍖呮嫭鍊掕鏁板櫒鐨勫悓姝ュ櫒锛屾帶鍒堕樆濉炵瓑寰呯殑鏂规硶锛屽€掕鏁板櫒鐨勯€掑噺鎿嶄綔鏂规硶绛?涓牳蹇冭绱犮€傚叾涓細
- 鍊掕鏁板櫒鐨勫悓姝ュ櫒锛氬熀浜嶢QS鍩虹鎶借薄闃熷垪鍚屾鍣ㄥ皝瑁呭唴缃疄鐜颁竴涓潤鎬佺殑鍐呯疆鍚屾绫?涓昏鐢ㄤ簬璁剧疆鍊掕鏁板櫒鐨勫垵濮嬪€间互鍙婂畾鍒禔QS鍩虹鍚屾鍣ㄧ殑鑾峰彇鍜岄噴鏀惧叡浜攣銆?/li>
- 鍊掕鏁板櫒鐨勫垵濮嬪€硷細 涓€鑸湪鏋勫缓CountDownLatch绫绘椂鎸囧畾锛岃〃绀虹殑鏄渶瑕佺瓑寰呮潯浠剁殑涓暟锛屽嵆灏辨槸鍊掕鏁板櫒鐨勫叿浣撶殑璧勬簮鏁伴噺Source(N)銆?/li>
- 鎺у埗绾跨▼闃诲绛夊緟鐨勬柟娉曪細瀹氫箟涓€涓帶鍒剁嚎绋嬮樆濉炵瓑寰呯殑鏂规硶锛屽綋鍊掕鏁板櫒鐨勫叿浣撶殑璧勬簮鏁伴噺 Source(N)>0鏃讹紝璋冪敤鏂规硶浣垮叾绾跨▼杩涘叆闃诲绛夊緟鐘舵€併€?/li>
- 鍊掕鏁板櫒鐨勯€掑噺鎿嶄綔鏂规硶锛氬畾涔変竴涓€掕鏁板櫒鐨勯€掑噺鎿嶄綔鏂规硶锛岃皟鐢ㄦ柟娉曞氨浼氭妸鍊掕鏁板櫒閫掑噺1锛屽綋鍊掕鏁板櫒鐨勫叿浣撶殑璧勬簮鏁伴噺 Source(N)-1=0鏃讹紝鎵€鏈夌瓑寰呯殑绾跨▼鎵嶅線涓嬬户缁墽琛屻€?/li>
绠€鍗曟潵璇达紝CountDownLatch涓昏鏄鏌愪釜绾跨▼鎴栬€呭涓嚎绋嬶紝绛夊緟鍏朵粬绾跨▼瀹屾垚鏌愪欢浜嬫儏鎴栬€呮煇涓换鍔＄粨鏉熶箣鍚庢墠鑳界户缁墽琛屻€?/p>
2. 鍩烘湰瀹炵幇
鍦–ountDownLatch绫荤殑JDK1.8鐗堟湰涓紝瀵逛簬CountDownLatch鐨勫熀鏈疄鐜板涓嬶細
public class CountDownLatch {
private final Sync sync;
/**
* CountDownLatch閿?鏋勯€犱竴涓€掕鏁板櫒
*/
public CountDownLatch(int count) {
if (count < 0) throw new IllegalArgumentException("count < 0");
this.sync = new Sync(count);
}
/**
* CountDownLatch閿?鍩轰簬AQS瀹氫箟鏀寔鍚屾鍣ㄥ疄鐜?
*/
private static class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = -5179523762034025860 L;
//......鍏朵粬鏂规硶浠ｇ爜
}
/**
* CountDownLatch閿?绾跨▼绛夊緟鏂规硶
*/
public void await() throws InterruptedException {
sync.acquireSharedInterruptibly(1);
}
/**
* CountDownLatch閿?鍊掕鏁板櫒閫掑噺鎿嶄綔
*/
public void countDown() {
sync.releaseShared(1);
}
//... 鍏朵粬浠ｇ爜
}
- 鍊掕鏁板櫒鍚屾鍣細鍩轰簬AQS鍩虹瀹氫箟鏀寔鍚屾鍣ㄥ疄鐜颁竴涓潤鎬佺鏈夊寲鐨勫悓姝ュ櫒Sync绫伙紝鍏朵腑瀹氫箟浜嗚幏鍙栧拰閲婃斁鍏变韩閿佺殑涓や釜鏂规硶
- 绾跨▼绛夊緟鏂规硶锛氫富瑕佹槸鎻愪緵浜嗕竴涓猘wait()鏂规硶锛屽叾鏈川鏄皟鐢ㄧ殑鏄疉QS鍩虹鍚屾鍣ㄤ腑鐨刟cquireSharedInterruptibly(int arg)鏂规硶锛屽惁鍒檛hrows InterruptedException寮傚父
- 鍊掕鏁板櫒閫掑噺鎿嶄綔鏂规硶锛?涓昏鏄彁渚涗簡涓€涓猚ountDown()鏂规硶锛屽叾鏈川鏄皟鐢ㄧ殑鏄疉QS鍩虹鍚屾鍣ㄤ腑鐨剅eleaseShared(int arg) 鏂规硶
2.1 鍩轰簬AQS鍚屾鍣ㄥ皝瑁呴潤鎬佸唴閮⊿ync鎶借薄绫?/h4>
/**
* CountDownLatch閿?鍩轰簬AQS鍚屾鍣ㄥ皝瑁呬竴涓唴閮ㄧ殑鍚屾鍣?
*/
private static final class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 4982264981922014374L;
Sync(int count) {
setState(count);
}
int getCount() {
return getState();
}
/**
* CountDownLatch閿?鑾峰彇鍏变韩閿佹柟娉?
*/
protected int tryAcquireShared(int acquires) {
return (getState() == 0) 1 : -1;
}
/**
* CountDownLatch閿?閲婃斁鍏变韩閿佹柟娉?
*/
protected boolean tryReleaseShared(int releases) {
// Decrement count; signal when transition to zero
for (;;) {
int c = getState();
if (c == 0)
return false;
int nextc = c-1;
if (compareAndSetState(c, nextc))
return nextc == 0;
}
}
}
- 瀹炵幇鏂瑰紡锛?涓昏鍩轰簬AQS灏佽鐨勫唴閮ㄩ潤鎬佹娊璞ync鍚屾绫诲疄鐜帮紝浣跨敤鐨凙QS鐨勫叡浜ā寮?/li>
- 涓昏鏂规硶锛?涓昏瀹氬埗閫傞厤鎻愪緵浜唗ryAcquireShared()鍜宼ryReleaseShared()鏂规硶锛屽嵆灏辨槸tryAcquireShared()鐢ㄤ簬鑾峰彇鍏变韩閿侊紝tryReleaseShared()鏂规硶鐢ㄤ簬閲婃斁鍏变韩閿侊紝鍏朵腑锛?
- 鑾峰彇鍏变韩閿乼ryAcquireShared()鏂规硶锛氶鍏堣幏鍙栫姸鎬佸彉閲弒tatus锛岃繖閲屾槸鎸囧€掕鏁板櫒涓殑鏁伴噺锛屽綋status=0鏃讹紝杩斿洖鍊?1锛岃〃绀鸿幏鍙栭攣鎴愬姛锛涘惁鍒欙紝status !=0 鏃讹紝杩斿洖鍊?-1锛岃〃绀鸿幏鍙栧叡浜攣澶辫触杩涜鍏ラ槦銆?/li>
- 閲婃斁鍏变韩閿乼ryReleaseShared()鏂规硶锛?閫氳繃鑷棆鏉ュ疄鐜伴€掑噺鎿嶄綔锛屽叾涓細鑾峰彇鐘舵€佸彉閲弒tatus锛屽皢鍏堕€掑噺1鍚庝娇鐢╟ompareAndSetState(c, nextc)鏂规硶閫氳繃CAS淇敼鐘舵€佸€?/li>
- 閿佽幏鍙栨柟寮忥細 涓昏鏄埄鐢╣etCount()鏉ヨ幏鍙栧€掕鏁板櫒涓殑鏁伴噺锛屽悓鏃惰繕鍙互鍒╃敤鏋勯€犳柟娉曟寚瀵间竴涓€掕鏁板櫒涓殑鏁伴噺銆?/li>
3. 鍏蜂綋瀹炵幇
public class CountDownLatch {
private final Sync sync;
/**
* CountDownLatch閿?鍩轰簬AQS鍩虹鍚屾鍣ㄥ疄鐜颁竴涓唴閮ㄥ悓姝ュ櫒
*/
private static final class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 4982264981922014374 L;
Sync(int count) {
setState(count);
}
int getCount() {
return getState();
}
protected int tryAcquireShared(int acquires) {
return (getState() == 0) 1 : -1;
}
protected boolean tryReleaseShared(int releases) {
// Decrement count; signal when transition to zero
for (;;) {
int c = getState();
if (c == 0)
return false;
int nextc = c - 1;
if (compareAndSetState(c, nextc))
return nextc == 0;
}
}
}
/**
* CountDownLatch閿?鏋勯€犱竴涓€掕鏁板櫒
*/
public CountDownLatch(int count) {
if (count < 0) throw new IllegalArgumentException("count < 0");
this.sync = new Sync(count);
}
/**
* CountDownLatch閿?鍩轰簬AQS瀹氫箟鏀寔鍚屾鍣ㄥ疄鐜?
*/
private static class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = -5179523762034025860 L;
//......鍏朵粬鏂规硶浠ｇ爜
}
/**
* CountDownLatch閿?绾跨▼绛夊緟鏂规硶
*/
public void await() throws InterruptedException {
sync.acquireSharedInterruptibly(1);
}
/**
* CountDownLatch閿?杩斿洖褰撳墠璁℃暟鍣?
*/
public long getCount() {
return sync.getCount();
}
/**
* CountDownLatch閿?绾跨▼绛夊緟鏂规硶(鏀寔瓒呮椂鏈哄埗)
*/
public boolean await(long timeout, TimeUnit unit)
throws InterruptedException {
return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
}
/**
* CountDownLatch閿?鍊掕鏁板櫒閫掑噺鎿嶄綔
*/
public void countDown() {
sync.releaseShared(1);
}
}
- 鍊掕鏁板垵濮嬪€硷細閫氳繃鏋勯€犳柟娉旵ountDownLatch(int count)鎸囧畾涓€涓€掕鏁板櫒鐨勫垵濮嬪€硷紝鍏跺繀椤诲ぇ浜?锛屽惁鍒欎細throw new IllegalArgumentException("count < 0")
- 绾跨▼绛夊緟鏂规硶锛?涓昏鎻愪緵浜哸wait() 鏂规硶鍜宎wait(long timeout, TimeUnit unit)鏂规硶锛屽叾涓細
- 鏃犲弬鏁癮wait() 鏂规硶锛?涓€鑸粯璁ょ殑鏂规硶锛屽叾鏈川鏄皟鐢ˋQS鍚屾鍣ㄤ腑鐨刟cquireSharedInterruptibly()鏂规硶锛屼富瑕佽〃绀烘敮鎸佷腑鏂満鍒?/li>
- 鏈夊弬鏁癮wait(long timeout, TimeUnit unit)鏂规硶锛?鏄敤浜庡疄鐜拌秴鏃舵満鍒讹紝鍏舵湰璐ㄦ槸璋冪敤AQS鍚屾鍣ㄤ腑鐨則ryAcquireSharedNanos(int arg, long nanosTimeout)鏂规硶
- 鍊掕鏁伴€掑噺鎿嶄綔鏂规硶锛氫富瑕佹槸countDown() 鏂规硶锛?鍏舵湰璐ㄦ槸璋冪敤AQS鍚屾鍣ㄤ腑鐨剅eleaseShared(int arg) 鏂规硶锛屾牳蹇冨疄鐜版槸AQS鍩虹鍚屾鍣ㄧ殑doReleaseShared鏂规硶銆?/li>
- 鍏朵粬鏂规硶锛?涓昏鏄痝etCount() 鏂规硶锛岀敤鏉ヨ幏鍙栧€掕鏁颁釜鏁帮紝鍏舵湰璐ㄦ槸璋冪敤AQS鍚屾鍣ㄤ腑getCount()鏂规硶锛屾潵鑾峰彇鐘舵€佸彉閲?/li>
/**
* CountDownLatch閿?鍩轰簬AQS鍚屾鍣ㄥ皝瑁呬竴涓唴閮ㄧ殑鍚屾鍣?
*/
private static final class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 4982264981922014374L;
Sync(int count) {
setState(count);
}
int getCount() {
return getState();
}
/**
* CountDownLatch閿?鑾峰彇鍏变韩閿佹柟娉?
*/
protected int tryAcquireShared(int acquires) {
return (getState() == 0) 1 : -1;
}
/**
* CountDownLatch閿?閲婃斁鍏变韩閿佹柟娉?
*/
protected boolean tryReleaseShared(int releases) {
// Decrement count; signal when transition to zero
for (;;) {
int c = getState();
if (c == 0)
return false;
int nextc = c-1;
if (compareAndSetState(c, nextc))
return nextc == 0;
}
}
}
- 鑾峰彇鍏变韩閿乼ryAcquireShared()鏂规硶锛氶鍏堣幏鍙栫姸鎬佸彉閲弒tatus锛岃繖閲屾槸鎸囧€掕鏁板櫒涓殑鏁伴噺锛屽綋status=0鏃讹紝杩斿洖鍊?1锛岃〃绀鸿幏鍙栭攣鎴愬姛锛涘惁鍒欙紝status !=0 鏃讹紝杩斿洖鍊?-1锛岃〃绀鸿幏鍙栧叡浜攣澶辫触杩涜鍏ラ槦銆?/li>
- 閲婃斁鍏变韩閿乼ryReleaseShared()鏂规硶锛?閫氳繃鑷棆鏉ュ疄鐜伴€掑噺鎿嶄綔锛屽叾涓細鑾峰彇鐘舵€佸彉閲弒tatus锛屽皢鍏堕€掑噺1鍚庝娇鐢╟ompareAndSetState(c, nextc)鏂规硶閫氳繃CAS淇敼鐘舵€佸€?/li>
public class CountDownLatch {
private final Sync sync;
/**
* CountDownLatch閿?鍩轰簬AQS鍩虹鍚屾鍣ㄥ疄鐜颁竴涓唴閮ㄥ悓姝ュ櫒
*/
private static final class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 4982264981922014374 L;
Sync(int count) {
setState(count);
}
int getCount() {
return getState();
}
protected int tryAcquireShared(int acquires) {
return (getState() == 0) 1 : -1;
}
protected boolean tryReleaseShared(int releases) {
// Decrement count; signal when transition to zero
for (;;) {
int c = getState();
if (c == 0)
return false;
int nextc = c - 1;
if (compareAndSetState(c, nextc))
return nextc == 0;
}
}
}
/**
* CountDownLatch閿?鏋勯€犱竴涓€掕鏁板櫒
*/
public CountDownLatch(int count) {
if (count < 0) throw new IllegalArgumentException("count < 0");
this.sync = new Sync(count);
}
/**
* CountDownLatch閿?鍩轰簬AQS瀹氫箟鏀寔鍚屾鍣ㄥ疄鐜?
*/
private static class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = -5179523762034025860 L;
//......鍏朵粬鏂规硶浠ｇ爜
}
/**
* CountDownLatch閿?绾跨▼绛夊緟鏂规硶
*/
public void await() throws InterruptedException {
sync.acquireSharedInterruptibly(1);
}
/**
* CountDownLatch閿?杩斿洖褰撳墠璁℃暟鍣?
*/
public long getCount() {
return sync.getCount();
}
/**
* CountDownLatch閿?绾跨▼绛夊緟鏂规硶(鏀寔瓒呮椂鏈哄埗)
*/
public boolean await(long timeout, TimeUnit unit)
throws InterruptedException {
return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
}
/**
* CountDownLatch閿?鍊掕鏁板櫒閫掑噺鎿嶄綔
*/
public void countDown() {
sync.releaseShared(1);
}
}
- 鏃犲弬鏁癮wait() 鏂规硶锛?涓€鑸粯璁ょ殑鏂规硶锛屽叾鏈川鏄皟鐢ˋQS鍚屾鍣ㄤ腑鐨刟cquireSharedInterruptibly()鏂规硶锛屼富瑕佽〃绀烘敮鎸佷腑鏂満鍒?/li>
- 鏈夊弬鏁癮wait(long timeout, TimeUnit unit)鏂规硶锛?鏄敤浜庡疄鐜拌秴鏃舵満鍒讹紝鍏舵湰璐ㄦ槸璋冪敤AQS鍚屾鍣ㄤ腑鐨則ryAcquireSharedNanos(int arg, long nanosTimeout)鏂规硶
缁间笂鎵€杩帮紝浠庝竴瀹氭剰涔変笂璁诧紝CountDownLatch鏄竴绉嶅叡浜攣锛屽睘浜嶢QS鍩虹鎶借薄闃熷垪鍚屾鍣ㄤ腑鍏变韩妯″紡瀛靛寲鐨勪骇鐗╋紝娌℃湁鏀寔鍏钩妯″紡涓庨潪鍏钩妯″紡鐨勫疄鐜般€?/p>
涓?CyclicBarrier(寰幆灞忛殰)鐨勮璁′笌瀹炵幇
鍦↗ava棰嗗煙涓紝CyclicBarrier(寰幆灞忛殰)鏄拡瀵逛簬Java澶氱嚎绋嬪苟鍙戞帶鍒朵腑鍊掕鏁板櫒鐨勭嚎绋嬫暟閲忥紝涓昏鏄噰鐢ㄩ€掑噺璁℃暟鏂瑰紡鐨勫€掕鏁板櫒鎬濇兂鍜屽熀浜嶢QS鍩虹鍚屾鍣ㄥ疄鐜扮殑ReentrantLock閿佹潵瀹炵幇鐨勪竴绉嶅悓姝ュ櫒宸ュ叿绫汇€?/p>
CyclicBarrier(寰幆灞忛殰)鏄疛ava涓€氳繃瀵圭嚎绋嬮瀹氫箟璁剧疆涓€涓睆闅滐紝鍙湁褰撳埌杈惧睆闅滅殑绾跨▼鏁伴噺鍒拌揪鎸囧畾鐨勬渶澶у睆闅滄椂锛屽睆闅滄墠浼氳杩欎簺绾跨▼閫氳繃鎵ц銆?lt;br />浠庝竴瀹氭剰涔変笂鏉ヨ锛岃繖閲岀殑灞忛殰鏈川涓婅繕鏄竴涓€掕鏁板櫒锛屽€掕鏁板櫒鐨勬渶澶ч檺搴︽敮鎸佺殑鏁伴噺灏辨槸鎴戜滑涓虹嚎绋嬭缃睆闅滃ぇ灏忥紝鍏跺伐浣滃師鐞嗕笌CountDownLatch(闂攣)绫讳技锛岄兘鏄€氳繃璁╃嚎绋嬮樆濉炵瓑寰呮椂锛屽€掕鏁板櫒鎵ц閫掑噺1杩愮畻銆?lt;br />浣嗘槸涓嶤ountDownLatch涓嶅悓鏄紝CyclicBarrier(寰幆灞忛殰)鏄熀浜嶳eentrantLock(鍙噸鍏ラ攣)鏉ュ疄鐜扮殑锛屾洿鍑嗙‘鐨勮锛孋yclicBarrier鏄ReentrantLock鐨勫簲鐢ㄥ疄渚嬨€?/p>
1. 璁捐鎬濇兂
涓€鑸潵璇达紝閫氳繃瀹氫箟涓€涓€掕鏁板櫒锛屼负浜嗚鏌愪釜绾跨▼鎴栬€呭涓嚎绋嬪湪鏌愪釜杩愯鑺傜偣涓婄害鏉烴涓嚎绋嬶紝闇€瑕佽鎸囧畾鏁伴噺鐨勭嚎绋嬪叡鍚屽埌杈炬煇涓€涓妭鐐逛箣鍚庯紝杩欎簺绾跨▼鎵嶄細涓€璧疯鎵ц銆?lt;br />CyclicBarrier(寰幆灞忛殰)鏈€鏃╂槸鍦↗DK1.5鐗堟湰涓彁渚涚殑锛屼粠璁捐鎬濇兂涓婃潵鐪嬶紝涓昏鍖呮嫭鍊掕鏁板櫒鐨勬渶澶у睆闅滐紝鎺у埗闃诲绛夊緟鐨勬柟娉曪紝鍊掕鏁板櫒鐨勯€掑噺鎿嶄綔鏂规硶锛屽拰瑙﹀彂鐐圭嚎绋嬩换鍔＄瓑4涓牳蹇冭绱犮€傚叾涓細
- 鍊掕鏁板櫒鐨勫悓姝ュ櫒锛?涓昏鍩轰簬ReentrantLock鏉ュ疄鐜版帶鍒剁嚎绋嬪璞★紝鍏舵湰璐ㄨ繕鏄熀浜嶢QS鍩虹鍚屾鍣ㄥ疄鐜般€?/li>
- 鍊掕鏁板櫒鐨勬渶澶у睆闅滄暟閲忥細涓€鑸槸鍦ㄦ瀯寤篊yclicBarrier(寰幆灞忛殰)瀵硅薄鏄瀹氫箟璁剧疆锛岃〃绀洪渶瑕佸湪鏌愪釜杩愯鑺傜偣涓婄害鏉熺殑绾跨▼鏁伴噺銆?/li>
- 鎺у埗绾跨▼闃诲绛夊緟鐨勬柟娉曪細瀹氫箟涓€涓柟娉曪紝浣垮緱瀹炵幇闃诲绾跨▼璁╁叾杩涘叆绛夊緟鐘舵€併€?/li>
- 鍊掕鏁板櫒鐨勯€掑噺鎿嶄綔鏂规硶锛氬畾涔変竴涓柟娉曪紝浣垮緱璁╁€掕鏁板櫒杩涜閫掑噺1杩愮畻锛岀洿鍒拌揪鍒板睆闅滄椂锛岀瓑寰呯殑绾跨▼鎵嶇户缁墽琛屻€?/li>
- 瑙﹀彂鐐圭嚎绋嬩换鍔★細涓€鑸寚鐨勬槸褰撴寚瀹氭暟閲忕殑绾跨▼杈惧埌璁剧疆鐨勫睆闅滄椂锛屾墠浼氬幓瑙﹀彂鎵ц鐨勪换鍔°€?/li>
绠€鍗曟潵璇达紝CyclicBarrier(寰幆灞忛殰)鏄澶氫釜绾跨▼浜掔浉绛夊緟锛岀洿鍒拌揪鍒颁竴涓悓姝ョ殑杩愯鑺傜偣銆傚啀缁х画涓€璧锋墽琛屻€?/p>
2. 鍩烘湰瀹炵幇
鍦–yclicBarrier绫荤殑JDK1.8鐗堟湰涓紝瀵逛簬CountDownLatch鐨勫熀鏈疄鐜板涓嬶細
public class CyclicBarrier {
/** CyclicBarrier閿佲€斿睆闅渓ock瀹炰綋 */
private final ReentrantLock lock = new ReentrantLock();
/** CyclicBarrier閿佲€斿睆闅滄潯浠堕槦鍒?*/
private final Condition trip = lock.newCondition();
/** CyclicBarrier閿佲€斿睆闅滄渶澶у€?*/
private final int parties;
/** CyclicBarrier閿佲€斿睆闅滆Е鍙戠嚎绋嬩换鍔＄洰鏍?*/
private final Runnable barrierCommand;
/** CyclicBarrier閿佲€斿綋鍓嶈鏁板櫒鐨勬渶澶у€煎睆闅滃疄渚?*/
private Generation generation = new Generation();
/** CyclicBarrier閿佲€斿綋鍓嶈鏁板櫒鐨勬渶澶у€煎睆闅滃疄渚?*/
private int count;
/** CyclicBarrier閿佲€斿睆闅滃疄渚?*/
private static class Generation {
boolean broken = false;
}
/** CyclicBarrier閿佲€旀瀯閫犱竴涓睆闅滃疄渚?涓嶅甫瑙﹀彂浠诲姟鐨? */
public CyclicBarrier(int parties) {
this(parties, null);
}
/** CyclicBarrier閿佲€旀瀯閫犱竴涓睆闅滃疄渚?甯﹁Е鍙戜换鍔＄殑) */
public CyclicBarrier(int parties, Runnable barrierAction) {
if (parties <= 0) throw new IllegalArgumentException();
this.parties = parties;
this.count = parties;
this.barrierCommand = barrierAction;
}
/** CyclicBarrier閿佲€旀棤鍙傛暟鏋勯€犱竴涓瓑寰呮柟娉?榛樿妯″紡) */
public int await() throws InterruptedException, BrokenBarrierException {
try {
return dowait(false, 0L);
} catch (TimeoutException toe) {
throw new Error(toe); // cannot happen
}
}
/** CyclicBarrier閿佲€旀湁鍙傛暟鏋勯€犱竴涓瓑寰呮柟娉?鏀寔瓒呮椂鏈哄埗) */
public int await(long timeout, TimeUnit unit)
throws InterruptedException,
BrokenBarrierException,
TimeoutException {
return dowait(true, unit.toNanos(timeout));
}
/** CyclicBarrier閿佲€旀洿鏂扮姸鎬佸彉閲?*/
private void nextGeneration() {
// signal completion of last generation
trip.signalAll();
// set up next generation
count = parties;
generation = new Generation();
}
/** CyclicBarrier閿佲€旈樆濉炲睆闅?*/
private void breakBarrier() {
generation.broken = true;
count = parties;
trip.signalAll();
}
//...鍏朵粬浠ｇ爜
}
- 棰勫畾涔夎缃睆闅滄渶澶у€硷細 涓昏鏄€氳繃鍙橀噺parties鏉ュ疄鐜伴瀹氫箟璁剧疆灞忛殰鏈€澶у€?/li>
- 璁剧疆褰撳墠灞忛殰鏁伴噺锛氫富瑕佹槸閫氳繃鍙橀噺count鏉ュ疄鐜?/li>
- 鎺у埗绾跨▼鐨勫璞″疄渚嬶細 涓昏鏄€氳繃ReentrantLock鍜孋ondition鏉ユ帶鍒剁嚎绋嬮棿閫氫俊
- 瑙﹀彂鐩爣浠诲姟瀵硅薄锛?涓昏鏄€氳繃Runable鏉ュ畾涔塨arrierCommand鍙橀噺
- 鎻愪緵浜嗕袱涓瀯閫犳柟娉曪細閮介渶瑕侀瀹氫箟鎸囧畾灞忛殰鏈€澶у€紁arties锛屽叾涓竴涓渶瑕佷紶鍏arrierAction瑙﹀彂鐐逛换鍔?/li>
- 绾跨▼闃诲绛夊緟鏂规硶锛氫富瑕佹彁渚涗簡2涓猘wait()鏂规硶锛屽叾涓細
- 鏃犲弬鏁癮wait()鏂规硶锛氶粯璁ゅ鐞嗘柟寮忥紝涓嶆敮鎸佽秴鏃舵満鍒讹紝鍏舵牳蹇冨鐞嗛€昏緫鍦╠owait(boolean timed, long nanos)鏂规硶涓疄鐜?/li>
- 鏈夊弬鏁癮wait()鏂规硶锛氭寚瀹氬弬鏁板鐞嗭紝鏀寔瓒呮椂鏈哄埗锛屽叾鏍稿績澶勭悊閫昏緫鍦╠owait(boolean timed, long nanos)鏂规硶涓疄鐜?/li>
- 灞忛殰璁剧疆鍏冲仴鏂规硶锛氫富瑕佹槸breakBarrier() 鏉ュ疄鐜帮紝鍏朵腑锛?
- 閫氱煡鍒拌揪灞忛殰鐨勬墍鏈夌嚎绋嬶細涓昏鏄€氳繃Condition涓殑signalAll()鏉ラ€氱煡灞忛殰涓墍鏈夌嚎绋嬪凡缁忔弧瓒虫潯浠?/li>
- 灞忛殰璁剧疆锛氶粯璁ら瀹氫箟璁剧疆灞忛殰鏈€澶у€间笌璁剧疆褰撳墠灞忛殰鏁扮浉鍚岋紝涓昏璁剧疆count = parties
- 鏇存柊灞忛殰鐘舵€侊細涓昏鏄€氳繃generation.broken = true鏉ュ疄鐜?/li>
- 鏇存柊灞忛殰鐨勭姸鎬侊細涓昏鏄彁渚涗簡nextGeneration() 鏂规硶锛岃〃绀哄凡缁忓埌杈鹃瀹氫箟璁剧疆灞忛殰鏈€澶у€硷紝鍏朵腑锛?
- 閫氱煡鍒拌揪灞忛殰鐨勬墍鏈夌嚎绋嬶細涓昏鏄€氳繃Condition涓殑signalAll()鏉ラ€氱煡灞忛殰涓墍鏈夌嚎绋嬪凡缁忔弧瓒虫潯浠?/li>
- 鍑嗗涓嬩竴杞睆闅滆缃細鎰忓懗鐫€棰勫畾涔夎缃睆闅滄渶澶у€间笌璁剧疆褰撳墠灞忛殰鏁扮浉鍚岋紝涓昏璁剧疆count = parties
- 閲嶇疆灞忛殰鐘舵€侊細涓昏鏄€氳繃generation = new Generation()鏉ュ疄鐜?/li>
2.1 鏋勯€燝eneration灞忛殰瀹炰緥鏍囪
private static class Generation {
boolean broken = false;
}
涓昏鏄瀯閫犱簡涓€涓潤鎬佺鏈夊寲鐨凣eneration绫伙紝鍏朵腑瀹氫箟浜嗕竴涓猙roken鍙橀噺鏉ヤ綔涓哄睆闅滄爣璁帮紝榛樿鍒濆鍊间负false锛岃〃绀鸿繕娌¤揪鍒板睆闅滄渶澶у€笺€?/p>
2.1 绾跨▼闃诲绛夊緟鏍稿績dowait鏂规硶
private int dowait(boolean timed, long nanos)
throws InterruptedException, BrokenBarrierException,
TimeoutException {
// [1].瀹炰緥鍖栨瀯寤篟eentrantLock鐨勫璞?
final ReentrantLock lock = this.lock;
// [2].閫氳繃lock()鑾峰彇閿佹垨鑰呰鍔犻攣鎿嶄綔
lock.lock();
try {
// [3].瀹炰緥鍖栨瀯寤篏eneration灞忛殰瀹炰緥瀵硅薄
final Generation g = generation;
// [4].鍒ゆ柇Generation灞忛殰瀹炰緥鏍囪鐘舵€?
if (g.broken)
throw new BrokenBarrierException();
// [5].鍒ゆ柇Thread鏄寘鍚腑鏂爣蹇椾綅
if (Thread.interrupted()) {
breakBarrier();
throw new InterruptedException();
}
// [6].瀵瑰€掕鏁板櫒鐨勫睆闅滄暟閲忛€掑噺1杩愮畻
int index = --count;
// [7].渚濇嵁缁撴灉index == 0琛ㄧず褰撳墠鎸囧畾鐨勭嚎绋嬫暟閲忓埌杈惧睆闅滄渶澶у€硷紝闇€瑕佽Е鍙慠unnable浠诲姟
if (index == 0) { // tripped
boolean ranAction = false;
try {
final Runnable command = barrierCommand;
if (command != null)
command.run();
ranAction = true;
// 杩涜涓嬩竴杞睆闅滆缃?
nextGeneration();
return 0;
} finally {
if (!ranAction)
breakBarrier();
}
}
// [7].鑷棆鎿嶄綔
for (;;) {
try {
// 鍒ゆ柇鏄惁瓒呮椂
if (!timed)
trip.await();
else if (nanos > 0L)
// 杩涜涓嬩竴杞睆闅滆缃?
nanos = trip.awaitNanos(nanos);
} catch (InterruptedException ie) {
if (g == generation && ! g.broken) {
breakBarrier();
throw ie;
} else {
// 鏄惁鍙戠敓绾跨▼涓柇
Thread.currentThread().interrupt();
}
}
if (g.broken)
throw new BrokenBarrierException();
if (g != generation)
return index;
// 濡傛灉绛夊緟鏃堕棿瓒呰繃鎸囧畾瓒呮椂鏃堕棿锛宼hrow new TimeoutException
if (timed && nanos <= 0L) {
breakBarrier();
throw new TimeoutException();
}
}
} finally {
// 鏈€鍚庨噴鏀鹃攣鎿嶄綔
lock.unlock();
}
}
- 鍔犻攣鎿嶄綔锛?瀹炰緥鍖栨瀯寤篟eentrantLock鐨勫璞★紝閫氳繃lock()鏂规硶杩涜鍔犻攣鎿嶄綔
- 鍒ゆ柇灞忛殰瀹炰緥鏍囪鐘舵€侊細瀹炰緥鍖栨瀯寤篏eneration瀹炰緥鏍囪锛屽垽鏂睆闅滃疄渚嬫爣璁扮姸鎬佹槸鍚︿竴鑷达紝濡傛灉涓嶄竴鑷村垯throw new BrokenBarrierException();
- 鍒ゆ柇褰撳墠绾跨▼鏄惁琚腑鏂細 鍒ゆ柇Thread鏄寘鍚腑鏂爣蹇椾綅锛屽鏋滀腑鏂璽hrow new InterruptedException()骞惰皟鐢╞reakBarrier()閲嶆柊璁剧疆灞忛殰
- 灞忛殰鍊掕鏁板櫒閫掑噺杩愮畻锛氬鍊掕鏁板櫒鐨勫睆闅滄暟閲忛€掑噺1杩愮畻锛屽嵆灏辨槸瀵瑰綋鍓嶅€掕鏁板櫒鐨勫綋鍓嶅€煎噺鍘?
- 瑙﹀彂鑺傜偣绾跨▼浠诲姟锛?褰撳墠鍊掕鏁板櫒鐨勫綋鍓嶅€间负0鏃讹紝闇€瑕佽Е鍙慠unnable浠诲姟锛屽苟璋冪敤nextGeneration鏂规硶寮€鍚笅涓€杞搷浣滐紱鍚﹀垯锛屽綋鍓嶅€掕鏁板櫒鐨勫綋鍓嶅€间笉涓?鏃讹紝璋冪敤awaitNanos(nanos)鏂规硶杩涘叆绛夊緟鐘舵€?/li>
- 鑷棆鎿嶄綔鍒ゆ柇瓒呮椂锛?濡傛灉浣跨敤浜嗚秴鏃跺弬鏁帮紝璋冪敤awaitNanos(nanos)鏂规硶杩涘叆绛夊緟鐘舵€侊紝鍏朵腑濡傛灉鍙戠敓涓柇鍒欒皟鐢═hread.currentThread().interrupt()璁剧疆涓柇鏍囪銆傚鏋滅瓑寰呮椂闂?gt; 鎸囧畾瓒呮椂鏃堕棿锛屾姏鍑簍hrow new TimeoutException()寮傚父
- 閲婃斁閿侊細 閫氳繃unlock()鏂规硶杩涜瑙ｉ攣鎿嶄綔锛屽苟閲婃斁閿?/li>
3. 鍏蜂綋瀹炵幇
鍦–yclicBarrier绫荤殑JDK1.8鐗堟湰涓紝瀵逛簬CyclicBarrier鐨勫叿浣撳疄鐜板涓嬶細
public class CyclicBarrier {
/** CyclicBarrier閿佲€斿睆闅渓ock瀹炰綋 */
private final ReentrantLock lock = new ReentrantLock();
/** CyclicBarrier閿佲€斿睆闅滄潯浠堕槦鍒?*/
private final Condition trip = lock.newCondition();
/** CyclicBarrier閿佲€斿睆闅滄渶澶у€?*/
private final int parties;
/** CyclicBarrier閿佲€斿睆闅滆Е鍙戠嚎绋嬩换鍔＄洰鏍?*/
private final Runnable barrierCommand;
/** CyclicBarrier閿佲€斿綋鍓嶈鏁板櫒鐨勬渶澶у€煎睆闅滃疄渚?*/
private Generation generation = new Generation();
/** CyclicBarrier閿佲€斿綋鍓嶈鏁板櫒鐨勬渶澶у€煎睆闅滃疄渚?*/
private int count;
/** CyclicBarrier閿佲€斿睆闅滃疄渚?*/
private static class Generation {
boolean broken = false;
}
/** CyclicBarrier閿佲€旀瀯閫犱竴涓睆闅滃疄渚?涓嶅甫瑙﹀彂浠诲姟鐨? */
public CyclicBarrier(int parties) {
this(parties, null);
}
/** CyclicBarrier閿佲€旀瀯閫犱竴涓睆闅滃疄渚?甯﹁Е鍙戜换鍔＄殑) */
public CyclicBarrier(int parties, Runnable barrierAction) {
if (parties <= 0) throw new IllegalArgumentException();
this.parties = parties;
this.count = parties;
this.barrierCommand = barrierAction;
}
/** CyclicBarrier閿佲€旀棤鍙傛暟鏋勯€犱竴涓瓑寰呮柟娉?榛樿妯″紡) */
public int await() throws InterruptedException, BrokenBarrierException {
try {
return dowait(false, 0L);
} catch (TimeoutException toe) {
throw new Error(toe); // cannot happen
}
}
/** CyclicBarrier閿佲€旀湁鍙傛暟鏋勯€犱竴涓瓑寰呮柟娉?鏀寔瓒呮椂鏈哄埗) */
public int await(long timeout, TimeUnit unit)
throws InterruptedException,
BrokenBarrierException,
TimeoutException {
return dowait(true, unit.toNanos(timeout));
}
/** CyclicBarrier閿佲€旀洿鏂扮姸鎬佸彉閲?*/
private void nextGeneration() {
// signal completion of last generation
trip.signalAll();
// set up next generation
count = parties;
generation = new Generation();
}
/** CyclicBarrier閿佲€旈樆濉炲睆闅?*/
private void breakBarrier() {
generation.broken = true;
count = parties;
trip.signalAll();
}
/** CyclicBarrier閿佲€旈樆濉炲睆闅?*/
private int dowait(boolean timed, long nanos)
throws InterruptedException, BrokenBarrierException,
TimeoutException {
// [1].瀹炰緥鍖栨瀯寤篟eentrantLock鐨勫璞?
final ReentrantLock lock = this.lock;
// [2].閫氳繃lock()鑾峰彇閿佹垨鑰呰鍔犻攣鎿嶄綔
lock.lock();
try {
// [3].瀹炰緥鍖栨瀯寤篏eneration灞忛殰瀹炰緥瀵硅薄
final Generation g = generation;
// [4].鍒ゆ柇Generation灞忛殰瀹炰緥鏍囪鐘舵€佹槸鍚︿负true
if (g.broken)
throw new BrokenBarrierException();
// [5].鍒ゆ柇Thread鏄寘鍚腑鏂爣蹇椾綅
if (Thread.interrupted()) {
breakBarrier();
throw new InterruptedException();
}
// [6].瀵瑰€掕鏁板櫒鐨勫睆闅滄暟閲忛€掑噺1杩愮畻
int index = --count;
// [7].渚濇嵁缁撴灉index == 0琛ㄧず褰撳墠鎸囧畾鐨勭嚎绋嬫暟閲忓埌杈惧睆闅滄渶澶у€硷紝闇€瑕佽Е鍙慠unnable浠诲姟
if (index == 0) { // tripped
boolean ranAction = false;
try {
final Runnable command = barrierCommand;
if (command != null)
command.run();
ranAction = true;
// 杩涜涓嬩竴杞睆闅滆缃?
nextGeneration();
return 0;
} finally {
if (!ranAction)
breakBarrier();
}
}
// [7].鑷棆鎿嶄綔
for (;;) {
try {
// 鍒ゆ柇鏄惁瓒呮椂
if (!timed)
trip.await();
else if (nanos > 0L)
nanos = trip.awaitNanos(nanos);
} catch (InterruptedException ie) {
if (g == generation && ! g.broken) {
breakBarrier();
throw ie;
} else {
Thread.currentThread().interrupt();
}
}
if (g.broken)
throw new BrokenBarrierException();
if (g != generation)
return index;
// 濡傛灉绛夊緟鏃堕棿瓒呰繃鎸囧畾瓒呮椂鏃堕棿锛宼hrow new TimeoutException
if (timed && nanos <= 0L) {
breakBarrier();
throw new TimeoutException();
}
}
} finally {
// 鏈€鍚庨噴鏀鹃攣鎿嶄綔
lock.unlock();
}
}
/** CyclicBarrier閿佲€旇幏鍙栧綋鍓嶇瓑灞忛殰绛夊緟鏁伴噺 */
public int getNumberWaiting() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return parties - count;
} finally {
lock.unlock();
}
}
/** CyclicBarrier閿佲€旇幏鍙栧綋鍓嶇瓑灞忛殰鏁伴噺 */
public int getParties() {
return parties;
}
/** CyclicBarrier閿佲€斿垽鏂綋鍓嶅睆闅?*/
public boolean isBroken() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return generation.broken;
} finally {
lock.unlock();
}
}
/** CyclicBarrier閿佲€旈噸缃睆闅滄暟閲?*/
public void reset() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
breakBarrier(); // break the current generation
nextGeneration(); // start a new generation
} finally {
lock.unlock();
}
}
}
涓昏闇€瑕佹敞鎰忓涓嬪嚑涓柟娉曪紝閮芥槸鍩轰簬ReentrantLock鏉ュ疄鐜板姞閿佸拰瑙ｉ攣鎿嶄綔鐨勶紝鍏朵腑锛?/p>
- getNumberWaiting()鏂规硶锛?鑾峰彇褰撳墠灞忛殰涓瓑寰呯殑绾跨▼鏁伴噺
- reset() 鏂规硶锛氬綋涓€杞睆闅滄搷浣滅粨鏉燂紝闇€瑕侀噸缃睆闅滀腑鏈€澶х嚎绋嬫暟閲?/li>
- isBroken() 鏂规硶锛氬垽鏂槸鍚﹀埌杈惧睆闅滄渶澶у€?/li>
缁间笂鎵€杩帮紝浠庝竴瀹氭剰涔変笂璁诧紝CyclicBarrier鏄竴绉嶅彲閲嶅叆閿侊紝灞炰簬ReentrantLock鐨勫簲鐢ㄥ疄渚嬶紝鍏朵腑鍔犻攣鍜岃В閿佹搷浣滈兘鏄嫭鍗犳ā寮忕殑銆?/p>
鍏?Semaphore(淇″彿閲?鐨勮璁′笌瀹炵幇
鍦↗ava棰嗗煙涓紝Semaphore(淇″彿閲?鏄拡瀵逛簬Java澶氱嚎绋嬪苟鍙戞帶鍒朵腑瀹炵幇瀵瑰叕鍏辫祫婧愮殑绾跨▼鏁伴噺杩涜骞跺彂鍚屾椂璁块棶鎺у埗锛屼富瑕佹槸閲囩敤鎸囧畾涓€涓渶澶ц鍙暟鐨勬€濇兂鍜屽熀浜嶢QS鍩虹鍚屾鍣ㄦ潵瀹炵幇鐨勪竴绉嶅悓姝ュ櫒宸ュ叿绫汇€?/p>
Semaphore鍙互鐢ㄦ潵鎺у埗鍦ㄥ悓涓€鏃跺埢璁块棶鍏变韩璧勬簮鐨勭嚎绋嬫暟閲忥紝閫氳繃鍗忚皟鍚勪釜绾跨▼浠ヤ繚璇佸叡浜祫婧愮殑鍚堢悊浣跨敤銆?lt;br />Semaphore缁存姢浜嗕竴缁勮櫄鎷熻鍙紝瀹冪殑鏁伴噺鍙互閫氳繃鏋勯€犲櫒鐨勫弬鏁版寚瀹氥€?lt;br />绾跨▼鍦ㄨ闂叡浜祫婧愬墠锛屽繀椤昏皟鐢⊿emaphore鐨刟cquire()鏂规硶鑾峰緱璁稿彲锛屽鏋滆鍙暟閲忎负0锛岃绾跨▼灏变竴鐩撮樆濉炪€?lt;br />绾跨▼鍦ㄨ闂叡浜祫婧愬悗锛屽繀椤昏皟鐢⊿emaphore鐨剅elease()鏂规硶閲婃斁璁稿彲銆?/p>
1. 璁捐鎬濇兂
涓€鑸潵璇达紝閫氳繃瀹氫箟涓€涓€掕鏁板櫒锛屼负浜嗘帶鍒舵渶澶歂涓嚎绋嬪悓鏃惰闂叕鍏辫祫婧愶紝鍏惰鏁板櫒鐨勬渶澶у€糓ax(N)鏄璁稿彲鐨勬渶澶歂涓嚎绋嬫暟閲忥紝鍗冲氨鏄鍙殑鏈€澶у€糔銆?lt;br />Semaphore绫绘渶鏃╂槸鍦↗DK1.5鐗堟湰鎻愪緵鐨勶紝浠庤璁℃€濇兂涓婃潵鐪嬶紝涓昏鍖呮嫭鍊掕鏁板櫒鐨勬渶澶ц鍙暟锛屽悓姝ュ櫒宸ヤ綔妯″紡锛岃幏鍙栭攣鏂规硶锛岄噴鏀鹃攣鏂规硶绛?涓牳蹇冭绱犮€傚叾涓細
- 鍚屾鍣ㄥ伐浣滄ā寮忥細鍩轰簬AQS鍩虹鎶借薄闃熷垪鍚屾鍣ㄥ皝瑁呭唴缃疄鐜颁竴涓潤鎬佺殑鍐呯疆鍚屾鍣ㄦ娊璞＄被锛岀劧鍚庡熀浜庤繖涓娊璞＄被鍒嗗埆瀹炵幇浜嗗叕骞冲悓姝ュ櫒鍜岄潪鍏钩鍚屾鍣紝鐢ㄦ潵鎸囧畾鍜屾弿杩板悓姝ュ櫒宸ヤ綔妯″紡鏄叕骞虫ā寮忚繕鏄潪鍏钩妯″紡銆?/li>
- 鍏钩/闈炲叕骞虫ā寮忥細涓昏鎻忚堪鐨勬槸澶氫釜绾跨▼鍦ㄥ悓鏃惰幏鍙栭攣鏃舵槸鍚︽寜鐓у厛鍒板厛寰楃殑椤哄簭鑾峰彇閿侊紝濡傛灉鏄垯涓哄叕骞虫ā寮忥紝鍚﹀垯涓洪潪鍏钩妯″紡銆?/li>
- 鑾峰彇閿佹柟娉曪細涓昏瀹氫箟浜嗕竴涓猯ock()鏂规硶鏉ヨ幏鍙栭攣锛岃〃绀哄亣濡傞攣宸茬粡琚叾浠栫嚎绋嬪崰鏈夋垨鎸佹湁锛屽叾褰撳墠鑾峰彇閿佺殑绾跨▼鍒欒繘鍏ョ瓑寰呯姸鎬併€?/li>
- 閲婃斁閿佹柟娉曪細涓昏瀹氫箟浜嗕竴涓猽nlock()鏂规硶鏉ラ噴鏀鹃攣锛岃〃绀哄亣濡傞攣宸茬粡琚叾浠栫嚎绋嬫斁寮冩垨閲婃斁锛屽叾褰撳墠鑾峰彇閿佺殑绾跨▼鍒欒幏寰楄閿併€?/li>
2. 鍩烘湰瀹炵幇
鍦↗DK1.8鐗堟湰涓紝瀵逛簬Semaphore鐨勫熀鏈疄鐜板涓嬶細
public class Semaphore implements java.io.Serializable {
private static final long serialVersionUID = -3222578661600680210 L;
/**
* Semaphore閿? 灏佽鍚屾鍣?
*/
private final Sync sync;
/**
* Semaphore閿? 灏佽鍚屾鍣?
*/
abstract static class Sync extends AbstractQueuedSynchronizer {
//....鍏朵粬浠ｇ爜
}
/**
* Semaphore閿? 鏋勯€犱竴涓护鐗岃鍙?榛樿闈炲叕妯″紡)
*/
public Semaphore(int permits) {
sync = new NonfairSync(permits);
}
/**
* Semaphore閿? 鏋勯€犱竴涓护鐗岃鍙?鍙€夊叕骞?闈炲叕妯″紡)
*/
public Semaphore(int permits, boolean fair) {
sync = fair new FairSync(permits) : new NonfairSync(permits);
}
/**
* Semaphore閿? 鑾峰彇閿佹柟娉?榛樿涓€涓笖鍙腑鏂満鍒?
*/
public void acquire() throws InterruptedException {
sync.acquireSharedInterruptibly(1);
}
/**
* Semaphore閿? 鑾峰彇閿佹柟娉?鍙€夋寚瀹氬涓笖鍙腑鏂満鍒?
*/
public void acquire(int permits) throws InterruptedException {
if (permits < 0) throw new IllegalArgumentException();
sync.acquireSharedInterruptibly(permits);
}
/**
* Semaphore閿? 鑾峰彇閿佹柟娉?榛樿澶氫釜涓斾笉鍙腑鏂満鍒?
*/
public void acquireUninterruptibly() {
sync.acquireShared(1);
}
/**
* Semaphore閿? 鑾峰彇閿佹柟娉?鎸囧畾澶氫釜涓斾笉鍙腑鏂満鍒?
*/
public void acquireUninterruptibly(int permits) {
if (permits < 0) throw new IllegalArgumentException();
sync.acquireShared(permits);
}
/**
* Semaphore閿?閲婃斁閿佹柟娉?榛樿涓€涓?
*/
public void release() {
sync.releaseShared(1);
}
/**
* Semaphore閿?閲婃斁閿佹柟娉?鍙€夋寚瀹氬涓?
*/
public void release(int permits) {
if (permits < 0) throw new IllegalArgumentException();
sync.releaseShared(permits);
}
}
- 鍐呴儴鍚屾鍣細鍩轰簬AQS鍩虹鍚屾鍣ㄥ皝瑁呭拰瀹氫箟浜嗕竴涓潤鎬佸唴閮⊿ync鎶借薄绫伙紝鍏朵腑鎶借薄浜嗕竴涓唴缃攣lock()鏂规硶
- 鍚屾鍣ㄥ伐浣滄ā寮忥細涓昏鎻愪緵浜?2涓瀯閫犳柟娉曪紝鍏朵腑鏃犲弬鏁版瀯閫犳柟娉曡〃绀虹殑鏄粯璁ょ殑宸ヤ綔妯″紡锛屾湁鍙傛暟鏋勯€犳柟娉曚富瑕佷緷鎹弬鏁版潵瀹炵幇鎸囧畾鐨勫伐浣滄ā寮?/li>
- 鑾峰彇閿佹柟娉曪細 涓昏鎻愪緵浜?涓熀浜巃cquire鏂规硶锛岀敤浜庤幏鍙栭攣鍏变韩閿侊紝鍏朵腑锛?
- 鏃犲弬鏁癮cquire()鏂规硶锛氳幏鍙栧叡浜攣鐨勪竴鑸ā寮忥紝榛樿鎸囧畾涓€涓鍙拰鏀寔鍙腑鏂満鍒?/li>
- 鏈夊弬鏁癮cquire()鏂规硶锛氳幏鍙栧叡浜攣鐨勬寚瀹氭ā寮忥紝鍙€夋寚瀹氬涓鍙笖鏀寔鍙腑鏂満鍒?/li>
- 鏃犲弬鏁癮cquireUninterruptibly()鏂规硶锛氳幏鍙栧叡浜攣鐨勬寚瀹氭ā寮忥紝榛樿鎸囧畾涓€涓鍙笖涓嶆敮鎸佸彲涓柇鏈哄埗
- 閲婃斁閿佹柟娉曪細 涓昏鏄彁渚涗簡2涓猺elease()鏂规硶鐢ㄤ簬閲婃斁閿佸叡浜攣锛屽叾涓細
- 鏃犲弬鏁皉elease()鏂规硶锛氶噴鏀惧叡浜攣鐨勪竴鑸ā寮忥紝榛樿鎸囧畾涓€涓鍙拰鏀寔鍙腑鏂満鍒?/li>
- 鏈夊弬鏁皉elease()鏂规硶锛氶噴鏀惧叡浜攣鐨勬寚瀹氭ā寮忥紝鍙€夋寚瀹氬涓鍙笖鏀寔鍙腑鏂満鍒?/li>
2.1 鍩轰簬AQS鍚屾鍣ㄥ皝瑁呴潤鎬佸唴閮⊿ync鎶借薄绫?/h4>
/**
* Semaphore閿? 鍩轰簬AQS鍩虹鍚屾鍣ㄥ皝瑁呭悓姝ュ櫒
*/
abstract static class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 1192457210091910933 L;
Sync(int permits) {
setState(permits);
}
final int getPermits() {
return getState();
}
/**
* Semaphore閿? 闈炲叕骞虫ā寮忚幏鍙栧叡浜攣
*/
final int nonfairTryAcquireShared(int acquires) {
for (;;) {
int available = getState();
int remaining = available - acquires;
if (remaining < 0 ||
compareAndSetState(available, remaining))
return remaining;
}
}
/**
* Semaphore閿? 閲婃斁鍏变韩閿?
*/
protected final boolean tryReleaseShared(int releases) {
for (;;) {
int current = getState();
int next = current + releases;
if (next < current) // overflow
throw new Error("Maximum permit count exceeded");
if (compareAndSetState(current, next))
return true;
}
}
/**
* Semaphore閿? 鑷棆+compareAndSetState閫氳繃CAS鎿嶄綔璁＄畻鎿嶄綔浠ょ墝璁稿彲鏁?
*/
final void reducePermits(int reductions) {
for (;;) {
int current = getState();
int next = current - reductions;
if (next > current) // underflow
throw new Error("Permit count underflow");
if (compareAndSetState(current, next))
return;
}
}
/**
* Semaphore閿? 鑷棆+compareAndSetState閫氳繃CAS鎿嶄綔閲嶇疆浠ょ墝璁稿彲鏁?
*/
final int drainPermits() {
for (;;) {
int current = getState();
if (current == 0 || compareAndSetState(current, 0))
return current;
}
}
}
- 瀹炵幇鏂瑰紡锛氫富瑕佹槸鍩轰簬AQS鍩虹鍚屾鍣ㄥ皝瑁呬簡涓€涓潤鎬佺殑鐨凷ync鎶借薄绫伙紝閫氳繃鏋勯€犳柟娉曟寚瀹氫竴涓渶澶х殑浠ょ墝璁稿彲鏁伴噺
- 涓昏鏂规硶锛氫富瑕佹槸鐪嬪叡浜攣鐨勮幏鍙杗onfairTryAcquireShared()鏂规硶鍜岄噴鏀鹃攣tryReleaseShared()鏂规硶锛屽叾涓細
- 鑾峰彇閿乶onfairTryAcquireShared()鏂规硶锛氶潪鍏钩妯″紡涓嬭幏鍙栧叡浜攣锛屽埄鐢ㄨ嚜鏃?compareAndSetState()鏂规硶閫氳繃CAS鎿嶄綔锛屼繚璇佸苟鍙戜慨鏀逛护鐗岃鍙暟閲?/li>
- 閲婃斁閿乼ryReleaseShared(i)鏂规硶锛?鍏钩/闈炲叕骞虫ā寮忎笅閲婃斁鍏变韩閿侊紝鍒╃敤鑷棆+compareAndSetState()鏂规硶閫氳繃CAS鎿嶄綔閲婃斁锛屼細鎶婇噴鏀剧殑浠ょ墝璁稿彲鏁伴噺澧炲姞鍒板綋鍓嶅墿浣欑殑浠ょ墝璁稿彲鏁伴噺涓€?/li>
- 浠ょ墝璁稿彲鎿嶄綔鏂规硶锛氫富瑕佹彁渚涗簡drainPermits() 鏂规硶 鍜宺educePermits() 鏂规硶锛屽叾涓細
- drainPermits() 鏂规硶锛氫富瑕佹槸鍒╃敤鑷棆+compareAndSetState()鏂规硶閫氳繃CAS鎿嶄綔閲嶇疆浠ょ墝璁稿彲鏁?/li>
- reducePermits() 鏂规硶锛氫富瑕佹槸鑷棆+compareAndSetState)鏂规硶閫氳繃CAS鎿嶄綔閫掑噺璁＄畻鎿嶄綔浠ょ墝璁稿彲鏁?/li>
- 鑾峰彇閿佹柟寮忥細浠ょ墝璁稿彲鏁伴噺QS鍩虹鍚屾鍣ㄧ姸鎬佸彉閲忓搴旓紝閫氳繃getPermits() 鏂规硶鏉ヨ幏鍙栦护鐗岃鍙暟閲忥紝鏈川鏄皟鐢ˋQS鍩虹鍚屾鍣ㄤ腑鐨刧etState()鏉ヨ幏鍙栫姸鎬佸彉閲忋€?/li>
鐗瑰埆鎸囧嚭鐨勬槸锛岃繖閲岀殑闈炲叕骞虫ā寮忎富瑕佹弿杩扮殑鏄紝鍦ㄤ护鐗岃鍙暟閲忓厑璁哥殑鎯呭喌涓嬶紝璁╂墍鏈夌嚎绋嬭繘琛岃嚜鏃嬫搷浣滐紝鍏跺疄灏辨槸涓嶅叧蹇冪嚎绋嬪埌鏉ョ殑椤哄簭锛屽皢鍏ㄩ儴绾跨▼鏀惧埌涓€璧峰幓鍙備笌绔炰簤浠ょ墝璁稿彲銆?lt;br />鍏朵腑锛屼富瑕佽繕鍒╃敤compareAndSetState鏂规硶鏉ヨ繘琛孋AS鎿嶄綔锛屼繚璇佷慨鏀逛护鐗岃鍙暟閲忕殑鍘熷瓙鎬ф搷浣溿€?lt;br />涓€鑸潵璇达紝鍋囪鎴戜滑鍏佽鎺у埗鐨勬渶澶х嚎绋嬫暟閲忎负N锛屽墿浣欎护鐗岃鍙暟閲忎负Remanent(N), 褰撳墠鍙敤浠ょ墝璁稿彲鏁伴噺涓篊urrent(N) , 娑堣€椾护鐗岃鍙暟閲忎负Reduction(N)锛岄偅涔堟垜浠細寰楀埌涓€涓绠楀叕寮忥細<br />
/**
* Semaphore閿? 鍩轰簬AQS鍩虹鍚屾鍣ㄥ皝瑁呭悓姝ュ櫒
*/
abstract static class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 1192457210091910933 L;
Sync(int permits) {
setState(permits);
}
final int getPermits() {
return getState();
}
/**
* Semaphore閿? 闈炲叕骞虫ā寮忚幏鍙栧叡浜攣
*/
final int nonfairTryAcquireShared(int acquires) {
for (;;) {
int available = getState();
int remaining = available - acquires;
if (remaining < 0 ||
compareAndSetState(available, remaining))
return remaining;
}
}
/**
* Semaphore閿? 閲婃斁鍏变韩閿?
*/
protected final boolean tryReleaseShared(int releases) {
for (;;) {
int current = getState();
int next = current + releases;
if (next < current) // overflow
throw new Error("Maximum permit count exceeded");
if (compareAndSetState(current, next))
return true;
}
}
/**
* Semaphore閿? 鑷棆+compareAndSetState閫氳繃CAS鎿嶄綔璁＄畻鎿嶄綔浠ょ墝璁稿彲鏁?
*/
final void reducePermits(int reductions) {
for (;;) {
int current = getState();
int next = current - reductions;
if (next > current) // underflow
throw new Error("Permit count underflow");
if (compareAndSetState(current, next))
return;
}
}
/**
* Semaphore閿? 鑷棆+compareAndSetState閫氳繃CAS鎿嶄綔閲嶇疆浠ょ墝璁稿彲鏁?
*/
final int drainPermits() {
for (;;) {
int current = getState();
if (current == 0 || compareAndSetState(current, 0))
return current;
}
}
}
- 鑾峰彇閿乶onfairTryAcquireShared()鏂规硶锛氶潪鍏钩妯″紡涓嬭幏鍙栧叡浜攣锛屽埄鐢ㄨ嚜鏃?compareAndSetState()鏂规硶閫氳繃CAS鎿嶄綔锛屼繚璇佸苟鍙戜慨鏀逛护鐗岃鍙暟閲?/li>
- 閲婃斁閿乼ryReleaseShared(i)鏂规硶锛?鍏钩/闈炲叕骞虫ā寮忎笅閲婃斁鍏变韩閿侊紝鍒╃敤鑷棆+compareAndSetState()鏂规硶閫氳繃CAS鎿嶄綔閲婃斁锛屼細鎶婇噴鏀剧殑浠ょ墝璁稿彲鏁伴噺澧炲姞鍒板綋鍓嶅墿浣欑殑浠ょ墝璁稿彲鏁伴噺涓€?/li>
- drainPermits() 鏂规硶锛氫富瑕佹槸鍒╃敤鑷棆+compareAndSetState()鏂规硶閫氳繃CAS鎿嶄綔閲嶇疆浠ょ墝璁稿彲鏁?/li>
- reducePermits() 鏂规硶锛氫富瑕佹槸鑷棆+compareAndSetState)鏂规硶閫氳繃CAS鎿嶄綔閫掑噺璁＄畻鎿嶄綔浠ょ墝璁稿彲鏁?/li>
<br />鍗冲氨鎰忓懗鐫€锛屽墿浣欎护鐗岃鍙暟閲忕瓑浜庡綋鍓嶅彲鐢ㄤ护鐗岃鍙暟閲忎笌娑堣€椾护鐗岃鍙暟閲忎箣宸€?lt;br />鐢辨鍙锛屽湪鍏钩/闈炲叕骞虫ā寮忎笅锛屾垜浠浜庡浜庤幏鍙栭攣鍜岄噴鏀鹃攣鏃讹紝瀵逛簬鍓╀綑浠ょ墝璁稿彲鏁伴噺Remanent(N)璁＄畻閮芥弧瓒充互涓嬪叕寮忥細
- 棣栧厛锛屽湪绾跨▼鍦ㄨ闂叡浜祫婧愬墠锛屾垜浠彲浠ュ厑璁哥殑鏈€澶у€间负Available(N),鑷棆鑾峰彇閿佺殑鏁伴噺涓篈cquires(N)锛岄偅涔堟垜浠湪鑾峰彇閿佹椂锛?/li>
- 鍏舵锛屽湪绾跨▼鍦ㄨ闂叡浜祫婧愬悗锛岃嚜鏃嬮噴鏀鹃攣鐨勬暟閲忎负Releases(N)锛岄偅涔堟垜浠湪閲婃斁閿佹椂锛?/li>
<br />褰撶劧锛岄渶瑕佹敞鎰忕殑鐨勪竴涓棶棰橈紝灏辨槸褰撳墿浣欎护鐗岃鍙暟閲廟emanent(N) < 0鏃讹紝琛ㄧず褰撳墠绾跨▼浼氳繘鍏ラ樆濉炵瓑寰呯姸鎬併€?/p>
2.2 鍩轰簬Sync鎶借薄绫诲皝瑁匜airSync鍏钩鍚屾鍣?/h4>
/**
* Semaphore閿? 鍩轰簬Sync鎶借薄绫诲皝瑁匜airSync鍏钩鍚屾鍣?
*/
static final class FairSync extends Sync {
private static final long serialVersionUID = 2014338818796000944 L;
/**
* Semaphore閿? Semaphore閿? 閫氳繃鏋勯€犳柟娉曟寚瀹氫护鐗岃鍙?
*/
FairSync(int permits) {
super(permits);
}
/**
* Semaphore閿? Semaphore閿? 鍏钩妯″紡閲婃斁鍏变韩閿?
*/
protected int tryAcquireShared(int acquires) {
for (;;) {
if (hasQueuedPredecessors())
return -1;
int available = getState();
int remaining = available - acquires;
if (remaining < 0 ||
compareAndSetState(available, remaining))
return remaining;
}
}
}
- 瀹炵幇鏂瑰紡锛?涓昏鏄湪鍩轰簬闈欐€佸唴閮⊿ync鎶借薄绫绘潵瀹炵幇锛屾瀯閫犱簡涓€涓彲鎸囧畾澶у皬鐨勭殑浠ょ墝璁稿彲
- 涓昏鏂规硶锛?涓昏鏄彁渚涗簡涓€涓猼ryAcquireShared鏂规硶锛屽叾涓埄鐢╤asQueuedPredecessors()鏉ヤ繚璇佸叕骞虫€?/li>
- 宸ヤ綔鏈哄埗锛?閫氳繃鍩轰簬AQS鍩虹鍚屾鍣ㄤ腑鐨勭瓑寰呴槦鍒楁潵瀹炵幇鍏钩鏈哄埗
/**
* Semaphore閿? 鍩轰簬Sync鎶借薄绫诲皝瑁匜airSync鍏钩鍚屾鍣?
*/
static final class FairSync extends Sync {
private static final long serialVersionUID = 2014338818796000944 L;
/**
* Semaphore閿? Semaphore閿? 閫氳繃鏋勯€犳柟娉曟寚瀹氫护鐗岃鍙?
*/
FairSync(int permits) {
super(permits);
}
/**
* Semaphore閿? Semaphore閿? 鍏钩妯″紡閲婃斁鍏变韩閿?
*/
protected int tryAcquireShared(int acquires) {
for (;;) {
if (hasQueuedPredecessors())
return -1;
int available = getState();
int remaining = available - acquires;
if (remaining < 0 ||
compareAndSetState(available, remaining))
return remaining;
}
}
}
闇€瑕佹敞鎰忕殑鏄紝鍦ㄦ湭杈惧埌鏈€澶х殑浠ょ墝璁稿彲鏁伴噺鏃讹紝鎵€鏈夌嚎绋嬮兘涓嶄細杩涘叆绛夊緟闃熷垪涓€?/p>
2.3 鍩轰簬Sync鎶借薄绫诲皝瑁匩onfairSync闈炲叕骞冲悓姝ュ櫒
/**
* Semaphore閿? 鍩轰簬Sync鎶借薄绫诲皝瑁匩onfairSync闈炲叕骞冲悓姝ュ櫒
*/
static final class NonfairSync extends Sync {
private static final long serialVersionUID = -2694183684443567898 L;
/**
* Semaphore閿? Semaphore閿? 閫氳繃鏋勯€犳柟娉曟寚瀹氫护鐗岃鍙?
*/
NonfairSync(int permits) {
super(permits);
}
/**
* Semaphore閿? Semaphore閿? 闈炲叕骞虫ā寮忛噴鏀惧叡浜攣
*/
protected int tryAcquireShared(int acquires) {
return nonfairTryAcquireShared(acquires);
}
}
- 瀹炵幇鏂瑰紡锛?涓昏鏄湪鍩轰簬闈欐€佸唴閮⊿ync鎶借薄绫绘潵瀹炵幇锛屾瀯閫犱簡涓€涓彲鎸囧畾澶у皬鐨勭殑浠ょ墝璁稿彲
- 涓昏鏂规硶锛?涓昏鏄彁渚涗簡涓€涓猼ryAcquireShared鏂规硶锛屽叾涓富瑕佹槸璋冪敤浜嗛潤鎬佸唴閮⊿ync鎶借薄绫籲onfairTryAcquireShared鏂规硶銆?/li>
- 宸ヤ綔鏈哄埗锛?閫氳繃鑷棆鎿嶄綔璁╂墍鏈夌嚎绋嬬珵浜夎幏鍙栦护鐗岃鍙紝鏈川杩樻槸閲囩敤浜咥QS鍩虹鍚屾鍣ㄤ腑闂叆绛栫暐鍒版墦鐮村叕骞崇殑
3. 鍏蜂綋瀹炵幇
鍦↗DK1.8鐗堟湰涓紝瀵逛簬Semaphore鐨勫叿浣撳疄鐜板涓嬶細
public class Semaphore implements java.io.Serializable {
private static final long serialVersionUID = -3222578661600680210 L;
/**
* Semaphore閿? 灏佽鍚屾鍣?
*/
private final Sync sync;
/**
* Semaphore閿? 鍩轰簬AQS鍩虹鍚屾鍣ㄥ皝瑁呭悓姝ュ櫒
*/
abstract static class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 1192457210091910933 L;
Sync(int permits) {
setState(permits);
}
final int getPermits() {
return getState();
}
/**
* Semaphore閿? 闈炲叕骞虫ā寮忚幏鍙栧叡浜攣
*/
final int nonfairTryAcquireShared(int acquires) {
for (;;) {
int available = getState();
int remaining = available - acquires;
if (remaining < 0 ||
compareAndSetState(available, remaining))
return remaining;
}
}
/**
* Semaphore閿? 閲婃斁鍏变韩閿?
*/
protected final boolean tryReleaseShared(int releases) {
for (;;) {
int current = getState();
int next = current + releases;
if (next < current) // overflow
throw new Error("Maximum permit count exceeded");
if (compareAndSetState(current, next))
return true;
}
}
/**
* Semaphore閿? 鑷棆+compareAndSetState閫氳繃CAS鎿嶄綔璁＄畻鎿嶄綔浠ょ墝璁稿彲鏁?
*/
final void reducePermits(int reductions) {
for (;;) {
int current = getState();
int next = current - reductions;
if (next > current) // underflow
throw new Error("Permit count underflow");
if (compareAndSetState(current, next))
return;
}
}
/**
* Semaphore閿? 鑷棆+compareAndSetState閫氳繃CAS鎿嶄綔閲嶇疆浠ょ墝璁稿彲鏁?
*/
final int drainPermits() {
for (;;) {
int current = getState();
if (current == 0 || compareAndSetState(current, 0))
return current;
}
}
}
/**
* Semaphore閿? 鍩轰簬Sync鎶借薄绫诲皝瑁匜airSync鍏钩鍚屾鍣?
*/
static final class FairSync extends Sync {
private static final long serialVersionUID = 2014338818796000944 L;
/**
* Semaphore閿? Semaphore閿? 閫氳繃鏋勯€犳柟娉曟寚瀹氫护鐗岃鍙?
*/
FairSync(int permits) {
super(permits);
}
/**
* Semaphore閿? Semaphore閿? 鍏钩妯″紡閲婃斁鍏变韩閿?
*/
protected int tryAcquireShared(int acquires) {
for (;;) {
if (hasQueuedPredecessors())
return -1;
int available = getState();
int remaining = available - acquires;
if (remaining < 0 ||
compareAndSetState(available, remaining))
return remaining;
}
}
}
/**
* Semaphore閿? 鍩轰簬Sync鎶借薄绫诲皝瑁匩onfairSync闈炲叕骞冲悓姝ュ櫒
*/
static final class NonfairSync extends Sync {
private static final long serialVersionUID = -2694183684443567898 L;
/**
* Semaphore閿? Semaphore閿? 閫氳繃鏋勯€犳柟娉曟寚瀹氫护鐗岃鍙?
*/
NonfairSync(int permits) {
super(permits);
}
/**
* Semaphore閿? Semaphore閿? 闈炲叕骞虫ā寮忛噴鏀惧叡浜攣
*/
protected int tryAcquireShared(int acquires) {
return nonfairTryAcquireShared(acquires);
}
}
/**
* Semaphore閿? 鏋勯€犱竴涓护鐗岃鍙?榛樿闈炲叕妯″紡)
*/
public Semaphore(int permits) {
sync = new NonfairSync(permits);
}
/**
* Semaphore閿? 鏋勯€犱竴涓护鐗岃鍙?鍙€夊叕骞?闈炲叕妯″紡)
*/
public Semaphore(int permits, boolean fair) {
sync = fair new FairSync(permits) : new NonfairSync(permits);
}
/**
* Semaphore閿? 鑾峰彇閿佹柟娉?榛樿涓€涓笖鍙腑鏂満鍒?
*/
public void acquire() throws InterruptedException {
sync.acquireSharedInterruptibly(1);
}
/**
* Semaphore閿? 鑾峰彇閿佹柟娉?鍙€夋寚瀹氬涓笖鍙腑鏂満鍒?
*/
public void acquire(int permits) throws InterruptedException {
if (permits < 0) throw new IllegalArgumentException();
sync.acquireSharedInterruptibly(permits);
}
/**
* Semaphore閿? 鑾峰彇閿佹柟娉?榛樿澶氫釜涓斾笉鍙腑鏂満鍒?
*/
public void acquireUninterruptibly() {
sync.acquireShared(1);
}
/**
* Semaphore閿? 鑾峰彇閿佹柟娉?鎸囧畾澶氫釜涓斾笉鍙腑鏂満鍒?
*/
public void acquireUninterruptibly(int permits) {
if (permits < 0) throw new IllegalArgumentException();
sync.acquireShared(permits);
}
/**
* Semaphore閿?閲婃斁閿佹柟娉?榛樿涓€涓?
*/
public void release() {
sync.releaseShared(1);
}
/**
* Semaphore閿?閲婃斁閿佹柟娉?鍙€夋寚瀹氬涓?
*/
public void release(int permits) {
if (permits < 0) throw new IllegalArgumentException();
sync.releaseShared(permits);
}
/**
* Semaphore閿?灏濊瘯鑾峰彇閿佹柟娉?榛樿涓€涓?
*/
public boolean tryAcquire() {
return sync.nonfairTryAcquireShared(1) >= 0;
}
/**
* Semaphore閿?灏濊瘯鑾峰彇閿佹柟娉?鍙€夋寚瀹氬涓?
*/
public boolean tryAcquire(int permits) {
if (permits < 0) throw new IllegalArgumentException();
return sync.nonfairTryAcquireShared(permits) >= 0;
}
/**
* Semaphore閿?灏濊瘯鑾峰彇閿佹柟娉?鍙€夋寚瀹氬涓苟涓旀敮鎸佽秴鏃舵満鍒?
*/
public boolean tryAcquire(int permits, long timeout, TimeUnit unit)
throws InterruptedException {
if (permits < 0) throw new IllegalArgumentException();
return sync.tryAcquireSharedNanos(permits, unit.toNanos(timeout));
}
/**
* Semaphore閿?灏濊瘯鑾峰彇閿佹柟娉?榛樿涓€涓苟涓旀敮鎸佽秴鏃舵満鍒?
*/
public boolean tryAcquire(long timeout, TimeUnit unit)
throws InterruptedException {
return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
}
/**
* Semaphore閿?缁熻鍙互浠ょ墝璁稿彲鏁?
*/
public int availablePermits() {
return sync.getPermits();
}
/**
* Semaphore閿?閲嶇疆浠ょ墝璁稿彲鏁?
*/
public int drainPermits() {
return sync.drainPermits();
}
/**
* Semaphore閿?閫掑噺璁＄畻浠ょ墝璁稿彲鏁?
*/
protected void reducePermits(int reduction) {
if (reduction < 0) throw new IllegalArgumentException();
sync.reducePermits(reduction);
}
/**
* Semaphore閿?鍒ゆ柇鏄惁鍏钩妯″紡
*/
public boolean isFair() {
return sync instanceof FairSync;
}
/**
* Semaphore閿?鍒ゆ柇闃熷垪涓槸鍚﹀瓨鍦ㄧ嚎绋嬪璞?
*/
public final boolean hasQueuedThreads() {
return sync.hasQueuedThreads();
}
/**
* Semaphore閿?鑾峰彇闃熷垪闀垮害
*/
public final int getQueueLength() {
return sync.getQueueLength();
}
/**
* Semaphore閿?鑾峰彇闃熷垪鐨勭嚎绋嬪璞?
*/
protected Collection < Thread > getQueuedThreads() {
return sync.getQueuedThreads();
}
}
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- 鏃犲弬鏁癮cquire()鏂规硶锛氫竴鑸ā寮忚幏鍙栧叡浜攣锛屼富瑕佹槸鍩轰簬AQS鍩虹鍚屾鍣ㄤ腑鐨刟cquireSharedInterruptibly(int arg)鏉ュ疄鐜帮紝鍏舵牳蹇冮€昏緫鏄痙oAcquireSharedInterruptibly(int arg)鏉ユ搷绾点€?/li>
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- 鏃犲弬鏁癮cquireUninterruptibly() 鏂规硶锛氫竴鑸ā寮忚幏鍙栧叡浜攣锛屼富瑕佹槸鍩轰簬AQS鍩虹鍚屾鍣ㄤ腑acquireShared(int arg)鏂规硶鏉ュ疄鐜帮紝鍏舵牳蹇冮€昏緫鏄痙oAcquireShared(int arg) 鏉ユ搷绾点€?/li>
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- 鏃犲弬鏁皌ryAcquire() 鏂规硶锛氶潪鍏钩妯″紡灏濊瘯鑾峰彇鍏变韩閿侊紝鐩存帴璋冪敤鐨勬槸闈炲叕骞冲悓姝ュ櫒涓殑nonfairTryAcquireShared(int acquires) 鏂规硶銆?/li>
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- 鍏钩妯″紡鑾峰彇閿佹柟寮忥細涓昏鎻愪緵浜?涓猼ryAcquire() 鏂规硶锛屾敮鎸佽秴鏃舵満鍒躲€傚叾涓細
- 鏃犲弬鏁皌ryAcquire() 鏂规硶锛氬叕骞虫ā寮忓皾璇曡幏鍙栧叡浜攣锛屼緷鎹寚瀹氫紶鍏ョ殑浠ょ墝璁稿彲鏁伴噺permits鏉ュ垽鏂紝褰損ermits< 0鏃讹紝鐩存帴throw new IllegalArgumentException()锛涘惁鍒欙紝鐩存帴璋冪敤鐨勬槸AQS鍩虹鍚屾鍣ㄤ腑鐨則ryAcquire(int permits, long timeout, TimeUnit unit)鏂规硶锛屽叾鏍稿績閫昏緫鏄痶ryAcquireSharedNanos(int arg, long nanosTimeout)鏉ユ搷绾点€?/li>
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- 閲婃斁閿佹搷浣滄柟寮忥細涓昏鎻愪緵浜?涓猺elease()鏂规硶,鍏朵腑锛?
- 鏃犲弬鏁皉elease() 鏂规硶锛氬叕骞?闈炲叕骞虫ā寮忕ず鑼冮攣鎿嶄綔锛岄粯璁ゆ敮鎸佷竴涓鍙紝涓昏鏄洿鎺ヨ皟鐢ˋQS鍩虹鍚屾鍣ㄤ腑鐨剅eleaseShared(int arg) 鏂规硶
- 鏈夊弬鏁皉elease() 鏂规硶锛氬叕骞?闈炲叕骞虫ā寮忕ず鑼冮攣鎿嶄綔锛屼緷鎹寚瀹氫紶鍏ョ殑浠ょ墝璁稿彲鏁伴噺permits鏉ュ垽鏂紝褰損ermits< 0鏃讹紝鐩存帴throw new IllegalArgumentException()锛涘惁鍒欙紝涓昏鏄洿鎺ヨ皟鐢ˋQS鍩虹鍚屾鍣ㄤ腑鐨剅eleaseShared(int arg) 鏂规硶
- 浠ょ墝璁稿彲鎿嶄綔鏂规硶锛氫富瑕佹彁渚涗簡availablePermits() 鏂规硶锛宺educePermits(int reduction)鏂规硶 浠ュ強drainPermits() 鏂规硶锛屽叾涓細
- availablePermits() 鏂规硶锛氳幏鍙栧彲鐢ㄧ殑浠ょ墝璁稿彲鏁伴噺锛屼富瑕佹槸璋冪敤鍐呴儴鍚屾鍣ㄤ腑getPermits()鏂规硶銆?/li>
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