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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>
浜?StampedLock(鍗版埑閿?鐨勮璁′笌瀹炵幇
鍦↗ava棰嗗煙涓紝StampedLock(鍗版埑閿?鏄拡瀵逛簬Java澶氱嚎绋嬪苟鍙戞帶鍒朵腑寮曞叆涓€涓叡浜攣瀹氫箟璇绘搷浣滀笌鐙崰閿佸畾涔夎鎿嶄綔绛夊満鏅叡鍚岀粍鍚堟瀯鎴愪竴鎶婇攣鏉ユ彁楂樺苟鍙戯紝涓昏鏄熀浜庤嚜瀹氫箟API鎿嶄綔瀹炵幇鐨勪竴绉嶅苟鍙戞帶鍒跺伐鍏风被銆?/p>
1. 璁捐鎬濇兂
<br />StampedLock锛堝嵃鎴抽攣锛夋槸瀵筊eentrantReadWriteLock璇诲啓閿佺殑涓€ 绉嶆敼杩涳紝涓昏鐨勬敼杩涗负锛氬湪娌℃湁鍐欏彧鏈夎鐨勫満鏅笅锛孲tampedLock鏀寔 涓嶇敤鍔犺閿佽€屾槸鐩存帴杩涜璇绘搷浣滐紝鏈€澶х▼搴︽彁鍗囪鐨勬晥鐜囷紝鍙湁鍦ㄥ彂 鐢熻繃鍐欐搷浣滀箣鍚庯紝鍐嶅姞璇婚攣鎵嶈兘杩涜璇绘搷浣溿€?lt;br />涓€鑸潵璇达紝StampedLock 閲岀殑鍐欓攣鍜屾偛瑙傝閿佸姞閿佹垚鍔熶箣鍚庯紝閮戒細杩斿洖涓€涓?stamp锛涚劧鍚庤В閿佺殑鏃跺€欙紝闇€瑕佷紶鍏ヨ繖涓?stamp銆?/p>
1.1 鍗版埑閿佺殑鍩烘湰鐞嗚
铏界劧鍩轰簬AQS鍩虹鍚屾鍣ㄥ疄鐜颁簡鍚勭閿侊紝浣嗘槸鐢变簬閲囩敤鐨勮嚜鏃嬮攣+CAS鎿嶄綔鏂瑰紡浼氬鑷村涓嬩袱涓棶棰橈細
- CAS鎭舵€х┖鑷棆浼氭氮璐瑰ぇ閲忕殑CPU璧勬簮
- 鍦⊿MP鏋舵瀯鐨凜PU涓婁細瀵艰嚧鈥滄€荤嚎椋庢毚鈥濋棶棰?/li>
瑙ｅ喅CAS鎭舵€х┖鑷棆鐨勬湁鏁堟柟寮忎箣涓€鏄互绌洪棿鎹㈡椂闂达紝杈冧负甯歌鐨?鏂规鏈変袱绉嶏細鍒嗘暎鎿嶄綔鐑偣鍜屼娇鐢ㄩ槦鍒楀墛宄般€?lt;br />鍩轰簬杩欎釜鍩虹锛屽湪JDK1.8鐗堟湰涓紝鍩轰簬浣跨敤闃熷垪鍓婂嘲鐨勬柟寮忥紝鑷畾涔堿PI鎿嶄綔锛屾彁渚涗簡StampedLock(鍗版埑閿?鐨勫疄鐜般€?lt;br />绠€鍗曟潵璇达紝StampedLock(鍗版埑閿?鎻愪緵浜嗕笁绉嶉攣鐨勫疄鐜版ā寮忥紝鍏朵腑锛?/p>
- 鎮茶璇婚攣锛氫笌ReadWriteLock鐨勮閿佺被浼硷紝澶氫釜绾跨▼鍙互鍚?鏃惰幏鍙栨偛瑙傝閿侊紝鎮茶璇婚攣鏄竴涓叡浜攣銆?/li>
- 涔愯璇婚攣锛氱浉褰撲簬鐩存帴鎿嶄綔鏁版嵁锛屼笉鍔犱换浣曢攣锛岃繛璇婚攣閮戒笉 瑕併€?/li>
- 鍐欓攣锛氫笌ReadWriteLock鐨勫啓閿佺被浼硷紝鍐欓攣鍜屾偛瑙傝閿佹槸浜?鏂ョ殑銆傝櫧鐒跺啓閿佷笌涔愯璇婚攣涓嶄細浜掓枼锛屼絾鏄湪鏁版嵁琚洿鏂颁箣鍚庯紝涔嬪墠 閫氳繃涔愯璇婚攣鑾峰緱鐨勬暟鎹凡缁忓彉鎴愪簡鑴忔暟鎹€?/li>
1.1 鍗版埑閿佺殑瀹炵幇鎬濇兂
StampedLock(鍗版埑閿?涓庡叾浠栨樉寮忛攣涓嶅悓鐨勬槸锛屼富瑕佹槸鏄渶鏃╁湪JDK1.8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鍏变韩鐘舵€佸彉閲忔満鍒讹紝鍐呯疆鐨勭瓑寰呮暟鎹槦鍒楋紝璇婚攣瑙嗗浘锛屽啓閿佽鍥句互鍙婅鍐欓攣瑙嗗浘绛?涓牳蹇冭绱犮€傚叾涓細
- 鍏变韩鐘舵€佸彉閲忔満鍒讹細涓昏鏄湪鍐呴儴灏佽涓€浜涢潤鎬佺鏈夌殑甯搁噺锛岀敤浜庢弿杩板悇涓ā寮忎箣闂寸殑鐘舵€佹弿杩扮瓑銆?/li>
- 鍐呯疆鐨勭瓑寰呮暟鎹槦鍒楋細涓昏鏄嚜瀹氫箟瀹炵幇涓€涓熀浜嶤LH閿佺殑绛夊緟闃熷垪
- 璇婚攣瑙嗗浘锛氬熀浜嶭ock鎺ュ彛瀹炵幇涓€涓搴旇閿佺殑瑙嗗浘
- 鍐欓攣瑙嗗浘锛氬熀浜嶭ock鎺ュ彛瀹炵幇涓€涓搴斿啓閿佺殑瑙嗗浘
- 璇诲啓閿佽鍥撅細鍩轰簬ReadWriteLock鎺ュ彛瀹炵幇涓€涓寘鍚閿佸拰鍐欓攣鐨勮鍥?/li>
2. 鍩烘湰瀹炵幇
鍦⊿tampedLock(鍗版埑閿?绫荤殑JDK1.8鐗堟湰涓紝瀵逛簬StampedLock鐨勫熀鏈疄鐜板涓嬶細
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
private static final long serialVersionUID = -6001602636862214147L;
/** StampedLock閿?鑷棆鎺у埗鐨勬渶澶у厑璁告牳蹇冪嚎绋嬫暟 */
private static final int NCPU = Runtime.getRuntime().availableProcessors();
/** StampedLock閿?绛夊緟闃熷垪鑷棆鎺у埗鐨勬渶澶ц嚜鏃嬮槇鍊?*/
private static final int SPINS = (NCPU > 1) 1 << 6 : 0;
/** StampedLock閿?绛夊緟闃熷垪澶磋妭鐐硅嚜鏃嬫帶鍒剁殑鏈€澶ц嚜鏃嬮槇鍊?*/
private static final int HEAD_SPINS = (NCPU > 1) 1 << 10 : 0;
/** StampedLock閿?绛夊緟闃熷垪澶磋妭鐐硅嚜鏃嬫帶鍒剁殑鏈€澶ц嚜鏃嬮槇鍊?*/
private static final int MAX_HEAD_SPINS = (NCPU > 1) 1 << 16 : 0;
/** StampedLock閿?杩涘叆闃诲涔嬪墠鐨勬渶澶ч噸璇曟鏁?*/
private static final int OVERFLOW_YIELD_RATE = 7; // must be power 2 - 1
//... 鍏朵粬閿佽祫婧愮殑鐘舵€佸父閲?
/** StampedLock閿?CLH闃熷垪鐨勫ご閮?head)鑺傜偣 */
private transient volatile WNode whead;
/** StampedLock閿?CLH闃熷垪鐨勫熬閮?tail)鑺傜偣 */
private transient volatile WNode wtail;
/** StampedLock閿?璇婚攣瑙嗗浘*/
transient ReadLockView readLockView;
/** StampedLock閿?鍐欓攣瑙嗗浘*/
transient WriteLockView writeLockView;
/** StampedLock閿?璇诲啓閿佽鍥?*/
transient ReadWriteLockView readWriteLockView;
/** StampedLock閿?閿佺殑鏈€鍘熷鐨勭姸鎬佸垵濮嬪€?*/
private static final long ORIGIN = WBIT << 1;
/** StampedLock閿?鍚勭閿佺殑鍚屾鐘舵€佸彉閲?*/
private transient volatile long state;
/** StampedLock閿?璇婚攣鐨勬孩鍑虹殑鎷撳睍鏍囪 */
private transient int readerOverflow;
/** StampedLock閿?鏋勯€犳柟娉?*/
public StampedLock() {
state = ORIGIN;
}
/** StampedLock閿?瀹炰緥鍖朢eadLock鏂规硶 */
public Lock asReadLock() {
ReadLockView v;
return ((v = readLockView) != null v :
(readLockView = new ReadLockView()));
}
/** StampedLock閿?瀹炰緥鍖朩riteLock鏂规硶 */
public Lock asWriteLock() {
WriteLockView v;
return ((v = writeLockView) != null v :
(writeLockView = new WriteLockView()));
}
/** StampedLock閿?瀹炰緥鍖朢eadWriteLock鏂规硶 */
public ReadWriteLock asReadWriteLock() {
ReadWriteLockView v;
return ((v = readWriteLockView) != null v :
(readWriteLockView = new ReadWriteLockView()));
}
/** StampedLock閿?鑾峰彇ReadLock鏂规硶 */
public long readLock() {
long s = state, next; // bypass acquireRead on common uncontended case
return ((whead == wtail && (s & ABITS) < RFULL &&
U.compareAndSwapLong(this, STATE, s, next = s + RUNIT)) ?
next : acquireRead(false, 0L));
}
/** StampedLock閿?鑾峰彇WriteLock鏂规硶 */
public long writeLock() {
long s, next; // bypass acquireWrite in fully unlocked case only
return ((((s = state) & ABITS) == 0L &&
U.compareAndSwapLong(this, STATE, s, next = s + WBIT)) ?
next : acquireWrite(false, 0L));
}
//... 鍏朵粬浠ｇ爜
}
2.1 鍏变韩鐘舵€佸彉閲忔満鍒?/h4>
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?鑷棆鎺у埗鐨勬渶澶у厑璁告牳蹇冪嚎绋嬫暟 */
private static final int NCPU = Runtime.getRuntime().availableProcessors();
/** StampedLock閿?绛夊緟闃熷垪鑷棆鎺у埗鐨勬渶澶ц嚜鏃嬮槇鍊?*/
private static final int SPINS = (NCPU > 1) 1 << 6 : 0;
/** StampedLock閿?绛夊緟闃熷垪澶磋妭鐐硅嚜鏃嬫帶鍒剁殑鏈€澶ц嚜鏃嬮槇鍊?*/
private static final int HEAD_SPINS = (NCPU > 1) 1 << 10 : 0;
/** StampedLock閿?绛夊緟闃熷垪澶磋妭鐐硅嚜鏃嬫帶鍒剁殑鏈€澶ц嚜鏃嬮槇鍊?*/
private static final int MAX_HEAD_SPINS = (NCPU > 1) 1 << 16 : 0;
/** StampedLock閿?杩涘叆闃诲涔嬪墠鐨勬渶澶ч噸璇曟鏁?*/
private static final int OVERFLOW_YIELD_RATE = 7; // must be power 2 - 1
// Values for lock state and stamp operations
/** StampedLock閿?璇婚攣绉诲姩鐨勪綅鏁?*/
private static final long RUNIT = 1L;
/** StampedLock閿?鍐欓攣绉诲姩鐨勪綅鏁?*/
private static final long WBIT = 1L << LG_READERS;
/** StampedLock閿?璇婚攣绉诲姩鐨勪綅鏁?*/
private static final long RBITS = WBIT - 1L;
/** StampedLock閿?璇婚攣绉诲姩鐨勪綅鏁?*/
private static final long RFULL = RBITS - 1L;
/** StampedLock閿?璇诲啓閿佺Щ鍔ㄧ殑浣嶆暟 */
private static final long ABITS = RBITS | WBIT;
/** StampedLock閿?璇诲啓閿佺Щ鍔ㄧ殑浣嶆暟 */
private static final long SBITS = ~RBITS;
// Special value from cancelled acquire methods so caller can throw IE
/** StampedLock閿?绾跨▼瀵硅薄涓柇鏍囪瘑 */
private static final long INTERRUPTED = 1L;
// Values for node status; order matters
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
private static final int WAITING = -1;
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
private static final int CANCELLED = 1;
// Modes for nodes (int not boolean to allow arithmetic)
/** StampedLock閿?鐢ㄤ簬琛ㄧず鍦ㄩ槦鍒椾箣涓槸璇绘ā寮?*/
private static final int RMODE = 0;
/** StampedLock閿?鐢ㄤ簬琛ㄧず鍦ㄩ槦鍒椾箣涓槸鍐欐ā寮?*/
private static final int WMODE = 1;
//... 鍏朵粬浠ｇ爜
// Unsafe mechanics
/** StampedLock閿?瀹炰緥鍖朥nsafe瀵硅薄 */
private static final sun.misc.Unsafe U;
/** StampedLock閿?鐘舵€?*/
private static final long STATE;
/** StampedLock閿?澶撮儴鑺傜偣 */
private static final long WHEAD;
/** StampedLock閿?灏鹃儴鑺傜偣 */
private static final long WTAIL;
/** StampedLock閿?鍚庣户鑺傜偣 */
private static final long WNEXT;
/** StampedLock閿?鑺傜偣鐘舵€?*/
private static final long WSTATUS;
/** StampedLock閿?鑺傜偣閾捐〃 */
private static final long WCOWAIT;
/** StampedLock閿?涓柇鏍囪瘑 */
private static final long PARKBLOCKER;
static {
try {
U = sun.misc.Unsafe.getUnsafe();
Class<?> k = StampedLock.class;
Class<?> wk = WNode.class;
STATE = U.objectFieldOffset
(k.getDeclaredField("state"));
WHEAD = U.objectFieldOffset
(k.getDeclaredField("whead"));
WTAIL = U.objectFieldOffset
(k.getDeclaredField("wtail"));
WSTATUS = U.objectFieldOffset
(wk.getDeclaredField("status"));
WNEXT = U.objectFieldOffset
(wk.getDeclaredField("next"));
WCOWAIT = U.objectFieldOffset
(wk.getDeclaredField("cowait"));
Class<?> tk = Thread.class;
PARKBLOCKER = U.objectFieldOffset
(tk.getDeclaredField("parkBlocker"));
} catch (Exception e) {
throw new Error(e);
}
}
}
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?鑷棆鎺у埗鐨勬渶澶у厑璁告牳蹇冪嚎绋嬫暟 */
private static final int NCPU = Runtime.getRuntime().availableProcessors();
/** StampedLock閿?绛夊緟闃熷垪鑷棆鎺у埗鐨勬渶澶ц嚜鏃嬮槇鍊?*/
private static final int SPINS = (NCPU > 1) 1 << 6 : 0;
/** StampedLock閿?绛夊緟闃熷垪澶磋妭鐐硅嚜鏃嬫帶鍒剁殑鏈€澶ц嚜鏃嬮槇鍊?*/
private static final int HEAD_SPINS = (NCPU > 1) 1 << 10 : 0;
/** StampedLock閿?绛夊緟闃熷垪澶磋妭鐐硅嚜鏃嬫帶鍒剁殑鏈€澶ц嚜鏃嬮槇鍊?*/
private static final int MAX_HEAD_SPINS = (NCPU > 1) 1 << 16 : 0;
/** StampedLock閿?杩涘叆闃诲涔嬪墠鐨勬渶澶ч噸璇曟鏁?*/
private static final int OVERFLOW_YIELD_RATE = 7; // must be power 2 - 1
// Values for lock state and stamp operations
/** StampedLock閿?璇婚攣绉诲姩鐨勪綅鏁?*/
private static final long RUNIT = 1L;
/** StampedLock閿?鍐欓攣绉诲姩鐨勪綅鏁?*/
private static final long WBIT = 1L << LG_READERS;
/** StampedLock閿?璇婚攣绉诲姩鐨勪綅鏁?*/
private static final long RBITS = WBIT - 1L;
/** StampedLock閿?璇婚攣绉诲姩鐨勪綅鏁?*/
private static final long RFULL = RBITS - 1L;
/** StampedLock閿?璇诲啓閿佺Щ鍔ㄧ殑浣嶆暟 */
private static final long ABITS = RBITS | WBIT;
/** StampedLock閿?璇诲啓閿佺Щ鍔ㄧ殑浣嶆暟 */
private static final long SBITS = ~RBITS;
// Special value from cancelled acquire methods so caller can throw IE
/** StampedLock閿?绾跨▼瀵硅薄涓柇鏍囪瘑 */
private static final long INTERRUPTED = 1L;
// Values for node status; order matters
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
private static final int WAITING = -1;
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
private static final int CANCELLED = 1;
// Modes for nodes (int not boolean to allow arithmetic)
/** StampedLock閿?鐢ㄤ簬琛ㄧず鍦ㄩ槦鍒椾箣涓槸璇绘ā寮?*/
private static final int RMODE = 0;
/** StampedLock閿?鐢ㄤ簬琛ㄧず鍦ㄩ槦鍒椾箣涓槸鍐欐ā寮?*/
private static final int WMODE = 1;
//... 鍏朵粬浠ｇ爜
// Unsafe mechanics
/** StampedLock閿?瀹炰緥鍖朥nsafe瀵硅薄 */
private static final sun.misc.Unsafe U;
/** StampedLock閿?鐘舵€?*/
private static final long STATE;
/** StampedLock閿?澶撮儴鑺傜偣 */
private static final long WHEAD;
/** StampedLock閿?灏鹃儴鑺傜偣 */
private static final long WTAIL;
/** StampedLock閿?鍚庣户鑺傜偣 */
private static final long WNEXT;
/** StampedLock閿?鑺傜偣鐘舵€?*/
private static final long WSTATUS;
/** StampedLock閿?鑺傜偣閾捐〃 */
private static final long WCOWAIT;
/** StampedLock閿?涓柇鏍囪瘑 */
private static final long PARKBLOCKER;
static {
try {
U = sun.misc.Unsafe.getUnsafe();
Class<?> k = StampedLock.class;
Class<?> wk = WNode.class;
STATE = U.objectFieldOffset
(k.getDeclaredField("state"));
WHEAD = U.objectFieldOffset
(k.getDeclaredField("whead"));
WTAIL = U.objectFieldOffset
(k.getDeclaredField("wtail"));
WSTATUS = U.objectFieldOffset
(wk.getDeclaredField("status"));
WNEXT = U.objectFieldOffset
(wk.getDeclaredField("next"));
WCOWAIT = U.objectFieldOffset
(wk.getDeclaredField("cowait"));
Class<?> tk = Thread.class;
PARKBLOCKER = U.objectFieldOffset
(tk.getDeclaredField("parkBlocker"));
} catch (Exception e) {
throw new Error(e);
}
}
}
瀵逛簬StampedLock閿佷腑瀵逛簬鍚勭璧勬簮鐨勬爣璁帮紝鍏跺皝瑁呬簡涓€绯诲垪鐨勫父閲忥紝涓昏鍙互鍒嗕负浠ヤ笅鍑犱釜鏂归潰锛屽叾涓細
- 鏍稿績璧勬簮甯搁噺鏍囪瘑锛氭槸瀵圭嚎绋嬫搷浣滆祫婧愮殑鎻愪緵鐨勫父閲忓皝瑁咃紝鍏朵腑锛?
- NCPU锛氳嚜鏃嬫帶鍒剁殑鏍稿績绾跨▼鏁伴噺锛屼富瑕侀€氳繃Runtime.getRuntime().availableProcessors()鑾峰彇璁剧疆銆?/li>
- SPINS锛氱瓑寰呴槦鍒楄嚜鏃嬫帶鍒剁殑鏈€澶ц嚜鏃嬮槇鍊硷紝涓昏閫氳繃 (_NCPU _> 1) 1 << 6 : 0鑾峰彇璁剧疆
- HEAD_SPINS锛?绛夊緟闃熷垪澶磋妭鐐硅嚜鏃嬫帶鍒剁殑鑷棆闃堝€硷紝涓昏閫氳繃 (_NCPU _> 1) 1 << 10 : 0鑾峰彇璁剧疆
- MAX_HEAD_SPINS锛氱瓑寰呴槦鍒楀ご鑺傜偣鑷棆鎺у埗鐨勬渶澶ц嚜鏃嬮槇鍊硷紝涓昏閫氳繃(_NCPU _> 1) 1 << 16 : 0鑾峰彇璁剧疆
- OVERFLOW_YIELD_RATE锛氱嚎绋嬭姝ユ搷浣滅瓑寰呯殑鑷棆闃堝€硷紝榛樿鍊间负7
- LG_READERS锛氳閿佹孩鍑虹殑鏈€澶ч槇鍊硷紝榛樿鍊间负7
- INTERRUPTED锛氱嚎绋嬩腑鏂爣璇嗭紝榛樿鍊间负1L
- 閿佺姸鎬佸€艰缃爣璇嗭細
- ORIGIN锛氶攣鐘舵€佺殑鍒濆鍊硷紝榛樿鍊间负WBIT << 1锛屽鏋滃垎閰嶅け璐ラ粯璁よ缃负0
- 閿佺姸鎬佺殑鎿嶄綔鏍囪瘑锛?
- RUNIT锛氳閿佺Щ鍔ㄧ殑浣嶆暟锛岄粯璁ゅ€间负 1
- WBIT锛氬啓閿佺Щ鍔ㄧ殑浣嶆暟锛岄粯璁ゅ€间负1L << LG_READERS
- RBITS锛氳閿佺Щ鍔ㄧ殑浣嶆暟锛?/em>榛樿鍊间负_WBIT _- 1L
- RFULL锛氱Щ鍔ㄧ殑浣嶆暟锛岄粯璁ゅ€间负_RBITS _- 1L
- ABITS锛氶攣绉诲姩鐨勪綅鏁帮紝榛樿鍊间负 _RBITS _| WBIT
- SBITS锛氶攣绉诲姩鐨勪綅鏁帮紝榛樿鍊间负 ~RBITS
- 绛夊緟闃熷垪鑺傜偣鏍囪瘑锛?
- WAITING锛氱瓑寰呯姸鎬佺殑鍒濆鍊硷紝榛樿鍊间负-1
- CANCELLED锛氬彇娑堢姸鎬佺殑鍒濆鍊硷紝榛樿鍊间负1
- 璇诲啓閿佺殑妯″紡鏍囪瘑锛?
- RMODE锛氳閿佹ā寮忥紝榛樿鍊间负0
- WMODE锛氬啓閿佹ā寮忥紝榛樿鍊间负1
- CAS鎿嶄綔鐘舵€佹爣璇嗭細灏佽浜咰AS鎿嶄綔鐘舵€佹爣璇嗭紝杩橀€氳繃鍙嶅皠瀹炰緥鍖栦簡Unsafe瀵硅薄瀹炰緥銆?/li>
2.2 鍐呯疆鐨勭瓑寰呴槦鍒梂Node
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** Wait nodes */
static final class WNode {
/** StampedLock閿?闃熷垪鍓嶉┍鑺傜偣 */
volatile WNode prev;
/** StampedLock閿?闃熷垪鍚庨┍鑺傜偣 */
volatile WNode next;
/** StampedLock閿?閿佺殑瀛樺偍鍒楄〃 */
volatile WNode cowait; // list of linked readers
/** StampedLock閿?绾跨▼瀵硅薄 */
volatile Thread thread; // non-null while possibly parked
/** StampedLock閿?閿佺殑鐘舵€?*/
volatile int status; // 0, WAITING, or CANCELLED
/** StampedLock閿?閿佺殑妯″紡 */
final int mode; // RMODE or WMODE
WNode(int m, WNode p) { mode = m; prev = p; }
}
/** Head of CLH queue */
/** StampedLock閿?澶撮儴鑺傜偣 */
private transient volatile WNode whead;
/** Tail (last) of CLH queue */
/** StampedLock閿?灏鹃儴鑺傜偣 */
private transient volatile WNode wtail;
}
瀵逛簬StampedLock閿佸浜庣瓑寰呴槦鍒楃殑瀹炵幇锛屼富瑕佸寘鍚互涓嬪嚑涓柟闈㈢殑鍐呭锛屽叾涓細<br />
- 灏佽浜嗕竴涓瓑寰呴槦鍒梂Node鐨勯潤鎬佸唴閮ㄧ被锛屽叾涓細
- prev锛氱瓑寰呴槦鍒楃殑鍓嶉┍鑺傜偣
- next锛氱瓑寰呴槦鍒楃殑鍚庨┍鑺傜偣
- cowait锛氳〃绀轰緷鎹攣鏍囪瀛樺偍褰撳墠绾跨▼鍏ラ槦鐨勬儏鍐碉紝闃熷垪閿佸垪琛?/li>
- thread锛?绾跨▼瀵硅薄锛屼竴鑸兘鏄綋鍓嶈幏鍙栭攣鐨勭嚎绋?/li>
- status锛氱敤浜庤〃绀洪攣鐨勭姸鎬佸彉閲忥紝瀵瑰簲鐫€甯搁噺0锛學AITING(-1), CANCELLED(1)锛屽叾涓紝0琛ㄧず姝ｅ父鐘舵€侊紝WAITING(-1)涓虹瓑寰呯姸鎬侊紝CANCELLED(1)涓哄彇娑堢姸鎬併€?/li>
- mode锛氱敤浜庤〃绀洪攣鐨勬ā寮忥紝瀵瑰簲鐫€甯搁噺RMODE鍜學MODE锛屽叾涓璕MODE涓哄啓妯″紡锛學MOD涓鸿妯″紡
- 鏋勯€犳柟娉昗Node(int m, WNode p)锛氱敤浜庡疄渚嬪寲WNode瀵硅薄锛屽疄鐜颁竴涓瓑寰呴槦鍒?/li>
- 瀹炰緥鍖栫瓑寰呴槦鍒楀璞★紝涓昏灏佽涓€涓ご閮ㄨ妭鐐箇head鍜屽熬閮ㄨ妭鐐箇tail鐨勫璞?/li>
2.3 鍏辩敤鐨勮閿佹牳蹇冨鐞嗛€昏緫
棣栧厛锛屽浜嶴tampedLock閿佺殑璇婚攣瑙嗗浘涓庡啓閿佽鍥剧殑闃熷垪鎿嶄綔锛屾湁涓€涓牳蹇冪殑澶勭悊閫昏緫锛?/p>
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?鍙栨秷鍏ラ槦鍒?*/
private long cancelWaiter(WNode node, WNode group, boolean interrupted) {
if (node != null && group != null) {
Thread w;
node.status = CANCELLED;
// unsplice cancelled nodes from group
for (WNode p = group, q; (q = p.cowait) != null;) {
if (q.status == CANCELLED) {
U.compareAndSwapObject(p, WCOWAIT, q, q.cowait);
p = group; // restart
}
else
p = q;
}
if (group == node) {
for (WNode r = group.cowait; r != null; r = r.cowait) {
if ((w = r.thread) != null)
U.unpark(w); // wake up uncancelled co-waiters
}
for (WNode pred = node.prev; pred != null; ) { // unsplice
WNode succ, pp; // find valid successor
while ((succ = node.next) == null ||
succ.status == CANCELLED) {
WNode q = null; // find successor the slow way
for (WNode t = wtail; t != null && t != node; t = t.prev)
if (t.status != CANCELLED)
q = t; // don't link if succ cancelled
if (succ == q || // ensure accurate successor
U.compareAndSwapObject(node, WNEXT,
succ, succ = q)) {
if (succ == null && node == wtail)
U.compareAndSwapObject(this, WTAIL, node, pred);
break;
}
}
if (pred.next == node) // unsplice pred link
U.compareAndSwapObject(pred, WNEXT, node, succ);
if (succ != null && (w = succ.thread) != null) {
succ.thread = null;
U.unpark(w); // wake up succ to observe new pred
}
if (pred.status != CANCELLED || (pp = pred.prev) == null)
break;
node.prev = pp; // repeat if new pred wrong/cancelled
U.compareAndSwapObject(pp, WNEXT, pred, succ);
pred = pp;
}
}
}
WNode h; // Possibly release first waiter
while ((h = whead) != null) {
long s; WNode q; // similar to release() but check eligibility
if ((q = h.next) == null || q.status == CANCELLED) {
for (WNode t = wtail; t != null && t != h; t = t.prev)
if (t.status <= 0)
q = t;
}
if (h == whead) {
if (q != null && h.status == 0 &&
((s = state) & ABITS) != WBIT && // waiter is eligible
(s == 0L || q.mode == RMODE))
release(h);
break;
}
}
return (interrupted || Thread.interrupted()) INTERRUPTED : 0L;
}
}
鍏舵锛屽浜嶴tampedLock閿佺殑璇婚攣瑙嗗浘鐨勫疄鐜颁綔鏉ョ湅锛屼富瑕佹牳蹇冨鐞嗗涓嬶細
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?鑾峰彇璇婚攣 */
private long acquireRead(boolean interruptible, long deadline) {
WNode node = null, p;
for (int spins = -1;;) {
WNode h;
if ((h = whead) == (p = wtail)) {
for (long m, s, ns;;) {
if ((m = (s = state) & ABITS) < RFULL ?
U.compareAndSwapLong(this, STATE, s, ns = s + RUNIT) :
(m < WBIT && (ns = tryIncReaderOverflow(s)) != 0L))
return ns;
else if (m >= WBIT) {
if (spins > 0) {
if (LockSupport.nextSecondarySeed() >= 0)
--spins;
}
else {
if (spins == 0) {
WNode nh = whead, np = wtail;
if ((nh == h && np == p) || (h = nh) != (p = np))
break;
}
spins = SPINS;
}
}
}
}
if (p == null) { // initialize queue
WNode hd = new WNode(WMODE, null);
if (U.compareAndSwapObject(this, WHEAD, null, hd))
wtail = hd;
}
else if (node == null)
node = new WNode(RMODE, p);
else if (h == p || p.mode != RMODE) {
if (node.prev != p)
node.prev = p;
else if (U.compareAndSwapObject(this, WTAIL, p, node)) {
p.next = node;
break;
}
}
else if (!U.compareAndSwapObject(p, WCOWAIT,
node.cowait = p.cowait, node))
node.cowait = null;
else {
for (;;) {
WNode pp, c; Thread w;
if ((h = whead) != null && (c = h.cowait) != null &&
U.compareAndSwapObject(h, WCOWAIT, c, c.cowait) &&
(w = c.thread) != null) // help release
U.unpark(w);
if (h == (pp = p.prev) || h == p || pp == null) {
long m, s, ns;
do {
if ((m = (s = state) & ABITS) < RFULL ?
U.compareAndSwapLong(this, STATE, s,
ns = s + RUNIT) :
(m < WBIT &&
(ns = tryIncReaderOverflow(s)) != 0L))
return ns;
} while (m < WBIT);
}
if (whead == h && p.prev == pp) {
long time;
if (pp == null || h == p || p.status > 0) {
node = null; // throw away
break;
}
if (deadline == 0L)
time = 0L;
else if ((time = deadline - System.nanoTime()) <= 0L)
return cancelWaiter(node, p, false);
Thread wt = Thread.currentThread();
U.putObject(wt, PARKBLOCKER, this);
node.thread = wt;
if ((h != pp || (state & ABITS) == WBIT) &&
whead == h && p.prev == pp)
U.park(false, time);
node.thread = null;
U.putObject(wt, PARKBLOCKER, null);
if (interruptible && Thread.interrupted())
return cancelWaiter(node, p, true);
}
}
}
}
for (int spins = -1;;) {
WNode h, np, pp; int ps;
if ((h = whead) == p) {
if (spins < 0)
spins = HEAD_SPINS;
else if (spins < MAX_HEAD_SPINS)
spins <<= 1;
for (int k = spins;;) { // spin at head
long m, s, ns;
if ((m = (s = state) & ABITS) < RFULL ?
U.compareAndSwapLong(this, STATE, s, ns = s + RUNIT) :
(m < WBIT && (ns = tryIncReaderOverflow(s)) != 0L)) {
WNode c; Thread w;
whead = node;
node.prev = null;
while ((c = node.cowait) != null) {
if (U.compareAndSwapObject(node, WCOWAIT,
c, c.cowait) &&
(w = c.thread) != null)
U.unpark(w);
}
return ns;
}
else if (m >= WBIT &&
LockSupport.nextSecondarySeed() >= 0 && --k <= 0)
break;
}
}
else if (h != null) {
WNode c; Thread w;
while ((c = h.cowait) != null) {
if (U.compareAndSwapObject(h, WCOWAIT, c, c.cowait) &&
(w = c.thread) != null)
U.unpark(w);
}
}
if (whead == h) {
if ((np = node.prev) != p) {
if (np != null)
(p = np).next = node; // stale
}
else if ((ps = p.status) == 0)
U.compareAndSwapInt(p, WSTATUS, 0, WAITING);
else if (ps == CANCELLED) {
if ((pp = p.prev) != null) {
node.prev = pp;
pp.next = node;
}
}
else {
long time;
if (deadline == 0L)
time = 0L;
else if ((time = deadline - System.nanoTime()) <= 0L)
return cancelWaiter(node, node, false);
Thread wt = Thread.currentThread();
U.putObject(wt, PARKBLOCKER, this);
node.thread = wt;
if (p.status < 0 &&
(p != h || (state & ABITS) == WBIT) &&
whead == h && node.prev == p)
U.park(false, time);
node.thread = null;
U.putObject(wt, PARKBLOCKER, null);
if (interruptible && Thread.interrupted())
return cancelWaiter(node, node, true);
}
}
}
}
}
鐒跺悗锛屽浜嶴tampedLock閿佺殑鍐欓攣瑙嗗浘鐨勫疄鐜颁綔鏉ョ湅锛屼富瑕佹牳蹇冨鐞嗗涓嬶細
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?鑾峰彇鍐欓攣 */
private long acquireWrite(boolean interruptible, long deadline) {
WNode node = null, p;
for (int spins = -1;;) { // spin while enqueuing
long m, s, ns;
if ((m = (s = state) & ABITS) == 0L) {
if (U.compareAndSwapLong(this, STATE, s, ns = s + WBIT))
return ns;
}
else if (spins < 0)
spins = (m == WBIT && wtail == whead) SPINS : 0;
else if (spins > 0) {
if (LockSupport.nextSecondarySeed() >= 0)
--spins;
}
else if ((p = wtail) == null) { // initialize queue
WNode hd = new WNode(WMODE, null);
if (U.compareAndSwapObject(this, WHEAD, null, hd))
wtail = hd;
}
else if (node == null)
node = new WNode(WMODE, p);
else if (node.prev != p)
node.prev = p;
else if (U.compareAndSwapObject(this, WTAIL, p, node)) {
p.next = node;
break;
}
}
for (int spins = -1;;) {
WNode h, np, pp; int ps;
if ((h = whead) == p) {
if (spins < 0)
spins = HEAD_SPINS;
else if (spins < MAX_HEAD_SPINS)
spins <<= 1;
for (int k = spins;;) { // spin at head
long s, ns;
if (((s = state) & ABITS) == 0L) {
if (U.compareAndSwapLong(this, STATE, s,
ns = s + WBIT)) {
whead = node;
node.prev = null;
return ns;
}
}
else if (LockSupport.nextSecondarySeed() >= 0 &&
--k <= 0)
break;
}
}
else if (h != null) { // help release stale waiters
WNode c; Thread w;
while ((c = h.cowait) != null) {
if (U.compareAndSwapObject(h, WCOWAIT, c, c.cowait) &&
(w = c.thread) != null)
U.unpark(w);
}
}
if (whead == h) {
if ((np = node.prev) != p) {
if (np != null)
(p = np).next = node; // stale
}
else if ((ps = p.status) == 0)
U.compareAndSwapInt(p, WSTATUS, 0, WAITING);
else if (ps == CANCELLED) {
if ((pp = p.prev) != null) {
node.prev = pp;
pp.next = node;
}
}
else {
long time; // 0 argument to park means no timeout
if (deadline == 0L)
time = 0L;
else if ((time = deadline - System.nanoTime()) <= 0L)
return cancelWaiter(node, node, false);
Thread wt = Thread.currentThread();
U.putObject(wt, PARKBLOCKER, this);
node.thread = wt;
if (p.status < 0 && (p != h || (state & ABITS) != 0L) &&
whead == h && node.prev == p)
U.park(false, time); // emulate LockSupport.park
node.thread = null;
U.putObject(wt, PARKBLOCKER, null);
if (interruptible && Thread.interrupted())
return cancelWaiter(node, node, true);
}
}
}
}
}
鏈€鍚庯紝缁煎悎瀵逛簬StampedLock閿佺殑璇婚攣鍜屽啓閿佺殑鑾峰彇鍜岄噴鏀剧瓑鎿嶄綔鏉ョ湅锛屼富瑕佹牳蹇冨鐞嗛兘浼氳皟鐢ㄤ互涓?涓柟娉曪紝鍏朵腑锛?/p>
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?璇婚攣婧㈠嚭閫掑澶勭悊鏂规硶 */
private long tryIncReaderOverflow(long s) {
// assert (s & ABITS) >= RFULL;
if ((s & ABITS) == RFULL) {
if (U.compareAndSwapLong(this, STATE, s, s | RBITS)) {
++readerOverflow;
state = s;
return s;
}
}
else if ((LockSupport.nextSecondarySeed() &
OVERFLOW_YIELD_RATE) == 0)
Thread.yield();
return 0L;
}
/** StampedLock閿?璇婚攣婧㈠嚭閫掑噺澶勭悊鏂规硶 */
private long tryDecReaderOverflow(long s) {
// assert (s & ABITS) >= RFULL;
if ((s & ABITS) == RFULL) {
if (U.compareAndSwapLong(this, STATE, s, s | RBITS)) {
int r; long next;
if ((r = readerOverflow) > 0) {
readerOverflow = r - 1;
next = s;
}
else
next = s - RUNIT;
state = next;
return next;
}
}
else if ((LockSupport.nextSecondarySeed() &
OVERFLOW_YIELD_RATE) == 0)
Thread.yield();
return 0L;
}
}
- tryIncReaderOverflow()鏂规硶锛氫富瑕佹槸瀹炵幇瀵逛簬閿佽幏鍙栬嚜鏃嬫椂鏈€澶ч噸璇曟鏁扮殑閫掑杩愮畻銆傚叾涓細
- 瀵逛簬婊¤冻stamp >= RFULL鏉′欢鏃讹紝鍒╃敤compareAndSwapLong()鏂规硶鏉ュ疄鐜癈AS鎿嶄綔鍔犳寔淇敼鐘舵€佸€笺€傚浜巖eaderOverflow浣滆嚜澧炶繍绠楀悗杩斿洖涓€涓?em>stamp锛屽彲鑳藉瓨鍦ㄦ洿鏂板拰閲婃斁鎿嶄綔銆?/em>
- 鍚﹀垯锛屽埄鐢↙ockSupport.nextSecondarySeed() 鍒ゆ柇锛屽浜庣嚎绋嬪仛璁╂澶勭悊锛岄粯璁よ繑鍥?
- tryDecReaderOverflow()鏂规硶锛氫富瑕佹槸瀹炵幇瀵逛簬閿佽幏鍙栬嚜鏃嬫椂鏈€澶ч噸璇曟鏁扮殑閫掑噺杩愮畻銆傚叾涓細
- 瀵逛簬婊¤冻stamp == RFULL鏉′欢鏃讹紝鍒╃敤compareAndSwapLong()鏂规硶鏉ュ疄鐜癈AS鎿嶄綔鍔犳寔淇敼鐘舵€佸€笺€傚浜巖eaderOverflow>0鍋氶€掑噺杩愮畻鍚庤繑鍥炰竴涓?em>stamp锛屽彲鑳藉瓨鍦ㄦ洿鏂板拰閲婃斁鎿嶄綔銆?/em>
- 鍚﹀垯锛屽埄鐢↙ockSupport.nextSecondarySeed() 鍒ゆ柇锛屽浜庣嚎绋嬪仛璁╂澶勭悊锛岄粯璁よ繑鍥?
2.4 鍩轰簬Lock鎺ュ彛瀹炵幇鐨凴eadLockView
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?ReadLockView */
final class ReadLockView implements Lock {
/** StampedLock閿?鑾峰彇閿?*/
public void lock() { readLock(); }
/** StampedLock閿?鑾峰彇鍙腑鏂攣 */
public void lockInterruptibly() throws InterruptedException {
readLockInterruptibly();
}
/** StampedLock閿?灏濊瘯鑾峰彇閿?*/
public boolean tryLock() { return tryReadLock() != 0L; }
/** StampedLock閿?灏濊瘯鑾峰彇鍙秴鏃堕攣 */
public boolean tryLock(long time, TimeUnit unit)
throws InterruptedException {
return tryReadLock(time, unit) != 0L;
}
/** StampedLock閿?閲婃斁 */
public void unlock() { unstampedUnlockRead(); }
/** StampedLock閿?涓嶆敮鎸佹潯浠跺彉閲忓畾涔?*/
public Condition newCondition() {
throw new UnsupportedOperationException();
}
}
/** StampedLock閿?瀹炰緥鍖朢eadLock鏂规硶 */
public Lock asReadLock() {
ReadLockView v;
return ((v = readLockView) != null v :
(readLockView = new ReadLockView()));
}
/** StampedLock閿?瀹炰緥鍖朢eadLock鏂规硶 */
public long readLock() {
long s = state, next; // bypass acquireRead on common uncontended case
return ((whead == wtail && (s & ABITS) < RFULL &&
U.compareAndSwapLong(this, STATE, s, next = s + RUNIT)) ?
next : acquireRead(false, 0L));
}
/** StampedLock閿?瀹炰緥鍖朢eadLock鏂规硶 */
public long tryReadLock() {
for (;;) {
long s, m, next;
if ((m = (s = state) & ABITS) == WBIT)
return 0L;
else if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, next = s + RUNIT))
return next;
}
else if ((next = tryIncReaderOverflow(s)) != 0L)
return next;
}
}
/** StampedLock閿?瀹炰緥鍖朢eadLock鏂规硶 */
public long tryReadLock(long time, TimeUnit unit)
throws InterruptedException {
long s, m, next, deadline;
long nanos = unit.toNanos(time);
if (!Thread.interrupted()) {
if ((m = (s = state) & ABITS) != WBIT) {
if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, next = s + RUNIT))
return next;
}
else if ((next = tryIncReaderOverflow(s)) != 0L)
return next;
}
if (nanos <= 0L)
return 0L;
if ((deadline = System.nanoTime() + nanos) == 0L)
deadline = 1L;
if ((next = acquireRead(true, deadline)) != INTERRUPTED)
return next;
}
throw new InterruptedException();
}
/** StampedLock閿?閲婃斁閿佹柟娉?*/
final void unstampedUnlockRead() {
// 鑷棆鎿嶄綔
for (;;) {
long s, m; WNode h;
if ((m = (s = state) & ABITS) == 0L || m >= WBIT)
throw new IllegalMonitorStateException();
else if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, s - RUNIT)) {
if (m == RUNIT && (h = whead) != null && h.status != 0)
release(h);
break;
}
}
else if (tryDecReaderOverflow(s) != 0L)
break;
}
}
}
瀵逛簬ReadLock鐨勫疄鐜帮紝涓昏鍖呭惈浠ヤ笅鍑犱釜鏂归潰鐨勫唴瀹癸紝鍏朵腑锛?/p>
- 鍩烘湰瀹炵幇鏂瑰紡锛氬熀浜嶭ock鎺ュ彛瀹炵幇锛屾彁渚涗簡瀵瑰簲鐨勯攣鑾峰彇鍜岄噴鏀炬搷浣滄柟娉曪紝鍏朵腑锛?
- lock()鏂规硶锛氫竴鑸ā寮忥紝涓昏閫氳繃StampedLock绫讳腑readLock()鏂规硶瀹炵幇
- lockInterruptibly()鏂规硶锛氬彲涓柇妯″紡锛屼富瑕侀€氳繃StampedLock绫讳腑readLockInterruptibly()鏂规硶瀹炵幇
- 鏃犲弬鏁皌ryLock() 鏂规硶锛氬皾璇曡幏鍙栭攣锛屼富瑕佷緷鎹甋tampedLock绫讳腑tryReadLock() != 0L鏉ュ疄鐜?/li>
- 鏈夊弬鏁皌ryLock() 鏂规硶锛氬皾璇曡幏鍙栭攣锛屼富瑕佷緷鎹甋tampedLock绫讳腑tryReadLock(long time, TimeUnit unit)!= 0L鏉ュ疄鐜?/li>
- unlock()鏂规硶锛氶攣鐨勯噴鏀撅紝涓昏閫氳繃StampedLock绫讳腑unstampedUnlockRead()鏂规硶瀹炵幇
- newCondition() 鏂规硶锛氫笉鏀寔鏉′欢鍙橀噺鐨勫畾涔夛紝榛樿璁剧疆鎶涘嚭UnsupportedOperationException
- 瀵瑰簲澶勭悊鏂规硶锛氫富瑕佹槸鍦⊿tampedLock澶栧眰瀹炵幇鐨勬搷浣滄柟娉曪紝鍏朵腑锛?
- readLock()鏂规硶锛氳閿佺殑瀹炵幇锛屼富瑕佹牳蹇冮€昏緫鍦╝cquireRead()鏂规硶
- tryReadLock()鏂规硶锛氬皾璇曡幏鍙栬閿侊紝鏍稿績澶勭悊閫昏緫鏄牴鎹搴旂殑鏉′欢杩斿洖瀵瑰簲鐨勯攣鐨刜stamp锛屽惁鍒欐姏鍑篲InterruptedException銆?/li>
- readLockInterruptibly()鏂规硶锛氳閿佺殑鍙腑鏂満鍒跺疄鐜帮紝鏍稿績澶勭悊閫昏緫鏄垽鏂嚎绋嬫槸鍚︿腑鏂互鍙婂埄鐢╝cquireRead鏂规硶楠岃瘉锛屾潯浠舵垚绔嬫椂锛岃繑鍥為攣鐨刜stamp锛屽惁鍒欐姏鍑篲InterruptedException銆?/li>
- unstampedUnlockRead()鏂规硶锛氶噴鏀鹃攣锛屾牳蹇冨鐞嗛€昏緫鑷棆鎿嶄綔+compareAndSwapLong瀹炵幇銆?/li>
2.5 鍩轰簬Lock鎺ュ彛瀹炵幇鐨刉riteLockView
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
final class WriteLockView implements Lock {
public void lock() { writeLock(); }
public void lockInterruptibly() throws InterruptedException {
writeLockInterruptibly();
}
public boolean tryLock() { return tryWriteLock() != 0L; }
public boolean tryLock(long time, TimeUnit unit)
throws InterruptedException {
return tryWriteLock(time, unit) != 0L;
}
public void unlock() { unstampedUnlockWrite(); }
public Condition newCondition() {
throw new UnsupportedOperationException();
}
}
/** StampedLock閿?瀹炰緥鍖朩riteLock鏂规硶 */
public Lock asWriteLock() {
WriteLockView v;
return ((v = writeLockView) != null v :
(writeLockView = new WriteLockView()));
}
}
瀵逛簬WriteLockView鐨勫疄鐜帮紝涓昏鍖呭惈浠ヤ笅鍑犱釜鏂归潰鐨勫唴瀹癸紝鍏朵腑锛?/p>
- 鍩烘湰瀹炵幇鏂瑰紡锛氬熀浜嶭ock鎺ュ彛瀹炵幇锛屾彁渚涗簡瀵瑰簲鐨勯攣鑾峰彇鍜岄噴鏀炬搷浣滄柟娉曪紝鍏朵腑锛?
- lock()鏂规硶锛氫竴鑸ā寮忥紝涓昏閫氳繃StampedLock绫讳腑WriteLock()鏂规硶瀹炵幇
- lockInterruptibly()鏂规硶锛氬彲涓柇妯″紡锛屼富瑕侀€氳繃StampedLock绫讳腑writeLockInterruptibly()鏂规硶瀹炵幇
- 鏃犲弬鏁皌ryLock() 鏂规硶锛氬皾璇曡幏鍙栭攣锛屼富瑕佷緷鎹甋tampedLock绫讳腑tryWriteLock() != 0L鏉ュ疄鐜?/li>
- 鏈夊弬鏁皌ryLock() 鏂规硶锛氬皾璇曡幏鍙栭攣锛屼富瑕佷緷鎹甋tampedLock绫讳腑tryWriteLock(long time, TimeUnit unit) != 0L鏉ュ疄鐜?/li>
- unlock()鏂规硶锛氶攣鐨勯噴鏀撅紝涓昏閫氳繃StampedLock绫讳腑unstampedUnlockWrite()鏂规硶瀹炵幇
- newCondition() 鏂规硶锛氫笉鏀寔鏉′欢鍙橀噺鐨勫畾涔夛紝榛樿璁剧疆鎶涘嚭UnsupportedOperationException
- 鏍稿績澶勭悊鏂规硶锛氫富瑕佹槸鍦⊿tampedLock澶栧眰瀹炵幇鐨勬搷浣滄柟娉曪紝鍏朵腑锛?
- writeLock()鏂规硶锛氬啓閿佺殑瀹炵幇锛屼富瑕佹牳蹇冮€昏緫鍦╝cquireWrite()鏂规硶
- tryWriteLock()鏂规硶锛氬皾璇曡幏鍙栧啓閿侊紝鏍稿績澶勭悊閫昏緫鏄牴鎹搴旂殑鏉′欢杩斿洖瀵瑰簲鐨勯攣鐨刜stamp锛屽惁鍒欐姏鍑篲InterruptedException銆?/li>
- writeLockInterruptibly()鏂规硶锛氬啓閿佺殑鍙腑鏂満鍒跺疄鐜帮紝鏍稿績澶勭悊閫昏緫鏄垽鏂嚎绋嬫槸鍚︿腑鏂互鍙婂埄鐢╝cquireWrite鏂规硶楠岃瘉锛屾潯浠舵垚绔嬫椂锛岃繑鍥為攣鐨刜stamp锛屽惁鍒欐姏鍑篲InterruptedException銆?/li>
- unstampedUnlockWrite()鏂规硶锛氶噴鏀鹃攣锛屾牳蹇冨鐞嗛€昏緫涓昏鏄€氳繃璋冪敤release(WNode h) 鏂规硶瀹炵幇銆?/li>
2.6 鍩轰簬ReadWriteLock鎺ュ彛瀹炵幇ReadWriteLockView
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?瀹炰緥鍖朢eadWriteLock鏂规硶 */
final class ReadWriteLockView implements ReadWriteLock {
/** StampedLock閿?ReadLock鏂规硶 */
public Lock readLock() { return asReadLock(); }
/** StampedLock閿?WriteLock鏂规硶 */
public Lock writeLock() { return asWriteLock(); }
}
/** StampedLock閿?瀹炰緥鍖朢eadWriteLock鏂规硶 */
public ReadWriteLock asReadWriteLock() {
ReadWriteLockView v;
return ((v = readWriteLockView) != null v :
(readWriteLockView = new ReadWriteLockView()));
}
}
瀵逛簬ReadWriteLockView鐨勫疄鐜帮紝涓昏鍖呭惈涓や釜閮ㄥ垎锛屽叾涓細
- 鍩轰簬ReadWriteLock鎺ュ彛瀹炵幇锛屼富瑕佹槸瀹炵幇readLock()鍜寃riteLock()鏂规硶
- 鍦╝sReadWriteLock()鏂规硶涓紝瀹炰緥鍖朢eadWriteLockView瀵硅薄
3. 鍏蜂綋瀹炵幇
瀵逛簬StampedLock鐨勫叿浣撳疄鐜帮紝鎴戜滑鍙互浠庡涓嬪嚑涓柟闈㈡媶瑙ｅ紑鏉ュ垎鏋愶細
- 鍏变韩閿丷eadLock閿佽幏鍙栨搷浣滃疄鐜帮細 闇€瑕佸尯鍒嗘偛瑙傝閿佸拰涔愯璇婚攣鐨勮幏鍙栦釜鏈変笉鍚岋紝涓€鑸湁榛樿鑾峰彇鏂瑰紡鍜屽皾璇曡幏鍙栦袱绉嶆柟寮忋€?/li>
- 鐙崰閿乄riteLock鍐欓攣鑾峰彇鎿嶄綔瀹炵幇锛?鍐欓攣涓庢偛瑙傝閿佷簰鏂ワ紝涓€鑸湁榛樿鑾峰彇鏂瑰紡鍜屽皾璇曡幏鍙栦袱绉嶆柟寮?/li>
- 鍏变韩閿丷eadLock閿侀噴鏀炬搷浣滃疄鐜帮細 涓€鑸垎涓哄叏閲婃斁鍜屽崐閲婃斁ReadLock閿佹搷浣滀袱绉嶆柟寮?/li>
- 鐙崰閿乄riteLock閿侀噴鏀炬搷浣滃疄鐜帮細涓€鑸垎涓哄叏閲婃斁鍜屽崐閲婃斁WriteLock閿佹搷浣滀袱绉嶆柟寮?/li>
鎺ヤ笅鏉ワ紝鎴戜滑渚夸粠鍏蜂綋鐨勪唬鐮佷腑鏉ュ垎鏋愪互涓婂唴瀹圭殑鍩烘湰瀹炵幇锛屼互鏂逛究鎴戜滑姝ｇ‘璁よ瘑鍜屼簡瑙tampedLock閿併€?/p>
3.1 鍏变韩閿丷eadLock璇婚攣鑾峰彇鎿嶄綔瀹炵幇
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?鎮茶璇婚攣-灏濊瘯鑾峰彇閿?榛樿妯″紡锛屼笉鏀寔瓒呮椂鏈哄埗) */
public long tryReadLock() {
// 閿佽嚜鏃嬭浆+compareAndSwapLong鏉AS鎿嶄綔鍔犳寔
for (;;) {
long s, m, next;
// [1].鐩存帴杩斿洖0
if ((m = (s = state) & ABITS) == WBIT)
return 0L;
// [2].compareAndSwapLong鏉AS鎿嶄綔鍔犳寔
else if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, next = s + RUNIT))
return next;
}
// [3].灏濊瘯鑾峰彇璇婚攣婧㈠嚭澶勭悊
else if ((next = tryIncReaderOverflow(s)) != 0L)
return next;
}
}
/** StampedLock閿?鎮茶璇婚攣-灏濊瘯鑾峰彇閿?鎸囧畾妯″紡锛屾敮鎸佽秴鏃舵満鍒? */
public long tryReadLock(long time, TimeUnit unit)
throws InterruptedException {
long s, m, next, deadline;
long nanos = unit.toNanos(time);
if (!Thread.interrupted()) {
if ((m = (s = state) & ABITS) != WBIT) {
if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, next = s + RUNIT))
return next;
}
else if ((next = tryIncReaderOverflow(s)) != 0L)
return next;
}
if (nanos <= 0L)
return 0L;
if ((deadline = System.nanoTime() + nanos) == 0L)
deadline = 1L;
if ((next = acquireRead(true, deadline)) != INTERRUPTED)
return next;
}
throw new InterruptedException();
}
/** StampedLock閿?涔愯璇婚攣-灏濊瘯鑾峰彇閿?*/
public long tryOptimisticRead() {
long s;
return (((s = state) & WBIT) == 0L) (s & SBITS) : 0L;
}
}
瀵逛簬璇婚攣鐨勮幏鍙栨潵璇达紝閮藉睘浜庢槸鍏变韩閿侊紝涓昏鎻愪緵浜嗕互涓嬪嚑绉嶆柟寮忥細
- 鏃犲弬鏁皌ryReadLock()鏂规硶锛氭偛瑙傝閿佺殑鑾峰彇鏂瑰紡锛岄粯璁ゆā寮忥紝涓嶆敮鎸佽秴鏃舵満鍒?/li>
- 鏈夊弬鏁皌ryReadLock()鏂规硶锛氭偛瑙傝閿佺殑鑾峰彇鏂瑰紡锛屾寚瀹氬弬鏁版ā寮忥紝鏀寔瓒呮椂鏈哄埗
- 鏃犲弬鏁皌ryOptimisticRead()鏂规硶锛氫箰瑙傝閿佺殑鑾峰彇鏂瑰紡锛屾病鏈夊姞閿佹搷浣?/li>
3.2 鐙崰閿乄riteLock鍐欓攣鑾峰彇鎿嶄綔瀹炵幇
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?鑾峰彇鍐欓攣鎿嶄綔(涓嶆敮鎸佽秴鏃舵満鍒? */
public long tryWriteLock() {
long s, next;
return ((((s = state) & ABITS) == 0L &&
U.compareAndSwapLong(this, STATE, s, next = s + WBIT)) ?
next : 0L);
}
/** StampedLock閿?鑾峰彇鍐欓攣鎿嶄綔(鏀寔瓒呮椂鏈哄埗) */
public long tryWriteLock(long time, TimeUnit unit)
throws InterruptedException {
long nanos = unit.toNanos(time);
if (!Thread.interrupted()) {
long next, deadline;
if ((next = tryWriteLock()) != 0L)
return next;
if (nanos <= 0L)
return 0L;
if ((deadline = System.nanoTime() + nanos) == 0L)
deadline = 1L;
if ((next = acquireWrite(true, deadline)) != INTERRUPTED)
return next;
}
throw new InterruptedException();
}
}
瀵逛簬鍐欓攣鐨勮幏鍙栨潵璇达紝閮藉睘浜庢槸鐙崰閿侊紝涓昏鎻愪緵浜嗕互涓嬪嚑绉嶆柟寮忥細
- 鏃犲弬鏁皌ryWriteLock()鏂规硶锛氶粯璁ゆā寮忥紝涓嶆敮鎸佽秴鏃舵満鍒?/li>
- 鏈夊弬鏁皌ryWriteLock()鏂规硶锛氭寚瀹氭ā寮忥紝渚濇嵁鍙傛暟鏉ュ疄鐜帮紝鏀寔瓒呮椂鏈哄埗
3.3 鍏变韩閿丷eadLock閲婃斁鎿嶄綔瀹炵幇
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?閲婃斁閿佹搷浣?*/
public void unlock(long stamp) {
long a = stamp & ABITS, m, s; WNode h;
while (((s = state) & SBITS) == (stamp & SBITS)) {
if ((m = s & ABITS) == 0L)
break;
else if (m == WBIT) {
if (a != m)
break;
state = (s += WBIT) == 0L ORIGIN : s;
if ((h = whead) != null && h.status != 0)
release(h);
return;
}
else if (a == 0L || a >= WBIT)
break;
else if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, s - RUNIT)) {
if (m == RUNIT && (h = whead) != null && h.status != 0)
release(h);
return;
}
}
else if (tryDecReaderOverflow(s) != 0L)
return;
}
throw new IllegalMonitorStateException();
}
/** StampedLock閿?閲婃斁璇婚攣 */
public void unlockRead(long stamp) {
long s, m; WNode h;
for (;;) {
if (((s = state) & SBITS) != (stamp & SBITS) ||
(stamp & ABITS) == 0L || (m = s & ABITS) == 0L || m == WBIT)
throw new IllegalMonitorStateException();
if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, s - RUNIT)) {
if (m == RUNIT && (h = whead) != null && h.status != 0)
release(h);
break;
}
}
else if (tryDecReaderOverflow(s) != 0L)
break;
}
}
/** StampedLock閿?鎮茶璇婚攣-杞崲鍗囩骇骞堕噴鏀惧鐞?*/
public long tryConvertToReadLock(long stamp) {
long a = stamp & ABITS, m, s, next; WNode h;
while (((s = state) & SBITS) == (stamp & SBITS)) {
if ((m = s & ABITS) == 0L) {
if (a != 0L)
break;
else if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, next = s + RUNIT))
return next;
}
else if ((next = tryIncReaderOverflow(s)) != 0L)
return next;
}
else if (m == WBIT) {
if (a != m)
break;
state = next = s + (WBIT + RUNIT);
if ((h = whead) != null && h.status != 0)
release(h);
return next;
}
else if (a != 0L && a < WBIT)
return stamp;
else
break;
}
return 0L;
}
/** StampedLock閿?涔愯璇婚攣-杞崲鍗囩骇骞堕噴鏀惧鐞?*/
public long tryConvertToOptimisticRead(long stamp) {
long a = stamp & ABITS, m, s, next; WNode h;
U.loadFence();
for (;;) {
if (((s = state) & SBITS) != (stamp & SBITS))
break;
if ((m = s & ABITS) == 0L) {
if (a != 0L)
break;
return s;
}
else if (m == WBIT) {
if (a != m)
break;
state = next = (s += WBIT) == 0L ORIGIN : s;
if ((h = whead) != null && h.status != 0)
release(h);
return next;
}
else if (a == 0L || a >= WBIT)
break;
else if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, next = s - RUNIT)) {
if (m == RUNIT && (h = whead) != null && h.status != 0)
release(h);
return next & SBITS;
}
}
else if ((next = tryDecReaderOverflow(s)) != 0L)
return next & SBITS;
}
return 0L;
}
public boolean tryUnlockRead() {
long s, m; WNode h;
while ((m = (s = state) & ABITS) != 0L && m < WBIT) {
if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, s - RUNIT)) {
if (m == RUNIT && (h = whead) != null && h.status != 0)
release(h);
return true;
}
}
else if (tryDecReaderOverflow(s) != 0L)
return true;
}
return false;
}
/** StampedLock閿?灏濊瘯閲婃斁璇婚攣 */
public boolean tryUnlockRead() {
long s, m; WNode h;
while ((m = (s = state) & ABITS) != 0L && m < WBIT) {
if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, s - RUNIT)) {
if (m == RUNIT && (h = whead) != null && h.status != 0)
release(h);
return true;
}
}
else if (tryDecReaderOverflow(s) != 0L)
return true;
}
return false;
}
}
瀵逛簬璇婚攣鐨勯噴鏀炬潵璇达紝涓昏鎻愪緵浜嗕互涓嬪嚑绉嶆柟寮忥細
- unlock() 鏂规硶锛氫緷鎹攣鐨勭姸鎬乻tatus鏉ュ尮閰嶅搴旈攣鐨剆tamp锛岀劧鍚庨噴鏀鹃攣鎿嶄綔
- unlockRead()鏂规硶锛?渚濇嵁閿佺殑鐘舵€乻tatus鏉ュ尮閰嶅搴旇閿佺殑stamp锛岀劧鍚庨噴鏀鹃攣鎿嶄綔
- tryUnlockRead()鏂规硶锛氶噴鏀惧綋鍓嶆寔鏈夌殑璇婚攣锛屼細璁剧疆涓€涓猻tamp鐒跺悗杩斿洖true锛屽惁鍒欙紝杩斿洖false
- tryConvertToReadLock()鏂规硶锛氫緷鎹攣鐨勭姸鎬乻tatus鏉ュ尮閰嶅搴旇閿佺殑stamp,鐒跺悗鏍规嵁瀵瑰簲鎯呭喌澶勭悊銆傚叾涓細
- 鍗曞啓閿佹ā寮忥細涓€鑸繑鍥炰竴涓搴旇閿佺殑stamp
- 鎮茶璇绘ā寮忥細鐩存帴杩斿洖瀵瑰簲璇婚攣鐨剆tamp
- 涔愯璇绘ā寮忥細闇€瑕佽幏鍙栦竴涓閿侊紝鐒跺悗鏄珛鍗宠繑鍥炲搴旇閿佺殑stamp
- tryConvertToOptimisticRead(): 渚濇嵁閿佺殑鐘舵€乻tatus鏉ュ尮閰嶅搴旇閿佺殑stamp,鐒跺悗杞崲鍗囩骇澶勭悊閲婃斁銆傚叾涓細
- 鎮茶璇绘ā寮忥細灞炰簬涓€鑸閿佹ā寮忥紝杩斿洖鐨勬槸妫€娴嬪埌瀵瑰簲璇婚攣鐨剆tamp
- 涔愯璇绘ā寮忥細闇€瑕佽繑鍥為€氳繃楠岃瘉鐨勫搴旇閿佺殑stamp
3.4 鐙崰閿乄riteLock鍐欓攣閲婃斁鎿嶄綔瀹炵幇
/** StampedLock閿?鏈€鏃╁湪JDK1.8涓疄鐜扮殑 */
public class StampedLock implements java.io.Serializable {
/** StampedLock閿?閿侀噴鏀炬柟娉?涓€鑸柟娉? */
public void unlock(long stamp) {
long a = stamp & ABITS, m, s; WNode h;
while (((s = state) & SBITS) == (stamp & SBITS)) {
if ((m = s & ABITS) == 0L)
break;
else if (m == WBIT) {
if (a != m)
break;
state = (s += WBIT) == 0L ORIGIN : s;
if ((h = whead) != null && h.status != 0)
release(h);
return;
}
else if (a == 0L || a >= WBIT)
break;
else if (m < RFULL) {
if (U.compareAndSwapLong(this, STATE, s, s - RUNIT)) {
if (m == RUNIT && (h = whead) != null && h.status != 0)
release(h);
return;
}
}
else if (tryDecReaderOverflow(s) != 0L)
return;
}
throw new IllegalMonitorStateException();
}
/** StampedLock閿?鍐欓攣閲婃斁鏂规硶 */
public void unlockWrite(long stamp) {
WNode h;
if (state != stamp || (stamp & WBIT) == 0L)
throw new IllegalMonitorStateException();
state = (stamp += WBIT) == 0L ORIGIN : stamp;
if ((h = whead) != null && h.status != 0)
release(h);
}
/** StampedLock閿?鍐欓攣杞崲鍗囩骇澶勭悊骞堕噴鏀鹃攣 */
public long tryConvertToWriteLock(long stamp) {
long a = stamp & ABITS, m, s, next;
while (((s = state) & SBITS) == (stamp & SBITS)) {
if ((m = s & ABITS) == 0L) {
if (a != 0L)
break;
if (U.compareAndSwapLong(this, STATE, s, next = s + WBIT))
return next;
}
else if (m == WBIT) {
if (a != m)
break;
return stamp;
}
else if (m == RUNIT && a != 0L) {
if (U.compareAndSwapLong(this, STATE, s,
next = s - RUNIT + WBIT))
return next;
}
else
break;
}
return 0L;
}
/** StampedLock閿?unlockWrite鐨勬牳蹇冨疄鐜?*/
private void release(WNode h) {
if (h != null) {
WNode q; Thread w;
U.compareAndSwapInt(h, WSTATUS, WAITING, 0);
if ((q = h.next) == null || q.status == CANCELLED) {
for (WNode t = wtail; t != null && t != h; t = t.prev)
if (t.status <= 0)
q = t;
}
if (q != null && (w = q.thread) != null)
U.unpark(w);
}
}
}
瀵逛簬鍐欓攣鐨勯噴鏀炬潵璇达紝涓昏鎻愪緵浜嗕互涓嬬鏂瑰紡锛?/p>
- unlock() 鏂规硶锛氫緷鎹攣鐨勭姸鎬乻tatus鏉ュ尮閰嶅搴旈攣鐨剆tamp锛岀劧鍚庨噴鏀鹃攣鎿嶄綔
- unlockWrite()鏂规硶锛氫緷鎹攣鐨勭姸鎬乻tatus鏉ュ尮閰嶅搴斿啓閿佺殑stamp锛岀劧鍚庨噴鏀鹃攣鎿嶄綔
- tryUnlockWrite()鏂规硶锛氶噴鏀惧綋鍓嶆寔鏈夌殑鍐欓攣锛屼細璁剧疆涓€涓猻tamp鐒跺悗杩斿洖true锛屽惁鍒欙紝杩斿洖false
- tryConvertToWriteLock()鏂规硶锛氫緷鎹攣鐨勭姸鎬乻tatus鏉ュ尮閰峴tamp锛屾牴鎹搴旈攣鐨勫仛鍗囩骇澶勭悊銆傚叾涓細
- 鍗曞啓閿佹ā寮忥細鐩存帴杩斿洖瀵瑰簲鐨勫啓閿佹爣璁皊tamp
- 璇诲啓閿佹ā寮忥細闇€瑕侀噴鏀捐閿侀攣锛屽苟杩斿洖瀵瑰簲鐨勫啓閿佹爣璁皊tamp
- 涔愯璇绘ā寮忥細鐩存帴杩斿洖瀵瑰簲鐨勫啓閿佹爣璁皊tamp
缁间笂鎵€杩帮紝StampedLock閿佹湰璐ㄤ笂渚濈劧鏄竴绉嶈鍐欓攣锛屽彧鏄病鏈夊熀浜嶢QS鍩虹鍚屾鍣ㄦ潵瀹炵幇锛屾槸鑷畾涔夊皝瑁匒PI鎿嶄綔瀹炵幇鐨勩€?/p>
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