jstack
jstack用於生成java虛擬機當前時刻的線程快照。線程快照是當前java虛擬機內每一條線程正在執行的方法堆棧的集合，生成線程快照的主要目的是定位線程出現長時間停頓的原因，如線程間死鎖、死循環、請求外部資源導致的長時間等待等。 線程出現停頓的時候通過jstack來查看各個線程的調用堆棧，就可以知道沒有響應的線程到底在后台做什么事情，或者等待什么資源。 如果java程序崩潰生成core文件，jstack工具可以用來獲得core文件的java stack和native stack的信息，從而可以輕松地知道java程序是如何崩潰和在程序何處發生問題。另外，jstack工具還可以附屬到正在運行的java程序中，看到當時運行的java程序的java stack和native stack的信息, 如果現在運行的java程序呈現hung的狀態，jstack是非常有用的。【線程分析】
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[root@localhost bin]
# jstack -help
Usage:
jstack [-l] <pid>
(to connect to running process)
jstack -F [-m] [-l] <pid>
(to connect to a hung process)
jstack [-m] [-l] <executable> <core>
(to connect to a core
file
)
jstack [-m] [-l] [server_id@]<remote server IP or
hostname
>
(to connect to a remote debug server)
Options:
-F to force a thread dump. Use when jstack <pid> does not respond (process is hung)
-m to print both java and native frames (mixed mode)
-l long listing. Prints additional information about locks
-h or -help to print this help message
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參數
-F：當正常輸出請求不被響應時，強制輸出線程棧堆。
-l：除線程棧堆外，顯示關於鎖的附加信息。
-m：如果調用本地方法的話，可以顯示c/c++的棧堆
示例
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[root@localhost bin]
# jstack -m 24971 | more
Attaching to process ID 24971, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.79-b02
Deadlock Detection:
No deadlocks found.
----------------- 24972 -----------------
0x00007fe07d2cd69d __GI___poll + 0x2d
0x00007fe070dc80a7 Java_java_net_PlainSocketImpl_socketAccept + 0x1e7
0x00007fe0745a3d98 * java.net.PlainSocketImpl.socketAccept(java.net.SocketImpl) bci:0 (Interpreted frame)
0x00007fe074597058 * java.net.AbstractPlainSocketImpl.accept(java.net.SocketImpl) bci:7 line:398 (Interpreted frame)
0x00007fe074597058 * java.net.ServerSocket.implAccept(java.net.Socket) bci:60 line:530 (Interpreted frame)
0x00007fe074597058 * java.net.ServerSocket.accept() bci:48 line:498 (Interpreted frame)
0x00007fe074597233 * org.apache.catalina.core.StandardServer.await() bci:180 line:470 (Interpreted frame)
0x00007fe074597706 * org.apache.catalina.startup.Catalina.await() bci:4 line:782 (Interpreted frame)
0x00007fe074597058 * org.apache.catalina.startup.Catalina.start() bci:209 line:728 (Interpreted frame)
0x00007fe0745914e7 <StubRoutines>
0x00007fe07c967e95 _ZN9JavaCalls11call_helperEP9JavaValueP12methodHandleP17JavaCallArgumentsP6Thread + 0x365
0x00007fe07c9668f8 _ZN9JavaCalls4callEP9JavaValue12methodHandleP17JavaCallArgumentsP6Thread + 0x28
0x00007fe07cbfdeef _ZN10Reflection6invokeE19instanceKlassHandle12methodHandle6Handleb14objArrayHandle9BasicTypeS3_bP6Thread + 0x
47f
0x00007fe07cbfeca0 _ZN10Reflection13invoke_methodEP7oopDesc6Handle14objArrayHandleP6Thread + 0x160
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