java - jstack线程转储是否一致？

Question

我从 jstack 获得了线程转储。它显示两个线程锁定在同一个对象上 locked <0x00000000c0313ce0> 。当 jstack 显示第一个线程的堆栈跟踪而不是在同一时刻显示第二个线程的堆栈跟踪时，是否有可能出现这种情况？或者还有什么原因会导致这种锁定情况？

"Thread-1" #44 prio=5 os_prio=0 tid=0x000000001c418800 nid=0x922c in Object.wait() [0x0000000018ffe000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    at org.h2.mvstore.db.MVTable.doLock1(MVTable.java:242)
    at org.h2.mvstore.db.MVTable.lock(MVTable.java:167)
    - locked <0x00000000c0313ce0> (a org.h2.engine.Database)
    at org.h2.engine.Database.lockMeta(Database.java:896)
    at org.h2.engine.Database.removeMeta(Database.java:919)
    - locked <0x00000000c0313ce0> (a org.h2.engine.Database)
    at org.h2.table.Table.removeChildrenAndResources(Table.java:525)
    at org.h2.mvstore.db.MVTable.removeChildrenAndResources(MVTable.java:799)
    at org.h2.engine.Session.cleanTempTables(Session.java:830)
    - locked <0x00000000c0313ce0> (a org.h2.engine.Database)
    at org.h2.engine.Session.close(Session.java:708)
    at org.h2.engine.Database.closeAllSessionsException(Database.java:1186)
    - locked <0x00000000c0313ce0> (a org.h2.engine.Database)
    at org.h2.engine.Database.close(Database.java:1224)
    - locked <0x00000000c0313ce0> (a org.h2.engine.Database)
    at org.h2.engine.DatabaseCloser.run(DatabaseCloser.java:63)

"Resource Destroyer in BasicResourcePool.close()" #110 daemon prio=5 os_prio=0 tid=0x000000001c41a000 nid=0x2d44 in Object.wait() [0x000000001b6ae000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    at org.h2.mvstore.db.MVTable.doLock1(MVTable.java:242)
    at org.h2.mvstore.db.MVTable.lock(MVTable.java:167)
    - locked <0x00000000c0313ce0> (a org.h2.engine.Database)
    at org.h2.engine.Database.lockMeta(Database.java:896)
    at org.h2.engine.Database.removeMeta(Database.java:919)
    - locked <0x00000000c0313ce0> (a org.h2.engine.Database)
    at org.h2.table.Table.removeChildrenAndResources(Table.java:525)
    at org.h2.mvstore.db.MVTable.removeChildrenAndResources(MVTable.java:799)
    at org.h2.engine.Session.cleanTempTables(Session.java:830)
    - locked <0x00000000c0313ce0> (a org.h2.engine.Database)
    at org.h2.engine.Session.close(Session.java:708)
    at org.h2.jdbc.JdbcConnection.close(JdbcConnection.java:383)
    - locked <0x00000000ede38ce0> (a org.h2.engine.Session)
    - locked <0x00000000ede37708> (a org.h2.jdbc.JdbcConnection)
    at com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:642)
    at com.mchange.v2.c3p0.impl.NewPooledConnection.closeMaybeCheckedOut(NewPooledConnection.java:255)
    - locked <0x00000000ee186430> (a com.mchange.v2.c3p0.impl.NewPooledConnection)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.destroyResource(C3P0PooledConnectionPool.java:621)
    - locked <0x00000000ee186490> (a java.lang.Object)
    at com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask.run(BasicResourcePool.java:1065)
    at com.mchange.v2.resourcepool.BasicResourcePool.destroyResource(BasicResourcePool.java:1090)
    at com.mchange.v2.resourcepool.BasicResourcePool.destroyResource(BasicResourcePool.java:1051)
    at com.mchange.v2.resourcepool.BasicResourcePool.access$100(BasicResourcePool.java:44)
    at com.mchange.v2.resourcepool.BasicResourcePool$5.run(BasicResourcePool.java:1305)

Answer 1

这两个线程没有锁定对象:它们都在对同一对象 o 的 o.wait() 调用中等待。

请记住，o.wait() 首先释放对象 o 上的锁。然后它等待其他线程通知该对象，然后在返回调用者之前重新获取锁。