c# - .NET 线程如何等待不属于任何线程的 syncblk？

Question

我的应用程序有一个故障转储，显示有一堆线程在等待 syncblk，而 syncblk 显示它没有拥有线程。这怎么可能？我正在尝试在测试应用程序中重现该症状，但我无法弄清楚产生该结果可能会发生什么......拥有线程退出或死亡而不释放 syncblk 仍然显示为拥有该对象，只是threadid是“XXX”......我已经通过pinvoke使用完全托管的优雅退出和硬线程终止进行了测试......我测试了一堆没有脉冲的等待的不同组合，不匹配的进入和退出......没有任何东西产生阻塞线程并且不显示所有者的 syncblk.....我的想法已经用完了

这是我试图复制的故障转储的输出:(注意索引 #1236)

0:000> !syncblk
Index         SyncBlock MonitorHeld Recursion Owning Thread Info          SyncBlock Owner
 784 0000000004f12eb0            3         1 000000000508a460  32a8  68   00000001a0a20510
 966 0000000004f06928            1         1 00000000052c5da0  2380 114   00000001df3080f8
1085 0000000004f23088            1         1 00000000052c8080  496c 120   00000001a0325238
1144 0000000005160d20            1         1 00000000050968b0   d74  56   00000000ff61b570
1151 0000000004f0c2c8            1         1 000000000508d8b0  3f64  77   000000017f66dc20
1236 0000000004f0b4f8           16         0 0000000000000000     none    000000019f1ec5d8
1261 0000000004f0ffe8            1         1 0000000008f18fc0  446c  94   000000013f8e70b0
1306 0000000004f0e918            1         1 00000000052c91f0  406c 123   000000011f5936f8
1318 0000000004f0e528            3         1 0000000008f1d580  24d8 106   000000015fc73f28
1329 0000000004f0cc58            1         1 0000000005095740  2fbc  53   000000011f36d320
1332 0000000004f15b38            1         1 0000000008f16710  3804  87   000000019f964728
1387 0000000004f22350            1         1 0000000008f18420  5180  92   00000001a008ab08
1515 0000000004f1d5d0            1         1 00000000052c4c30  2b5c 111   00000000ffd3c068
1594 0000000004f19bc0            1         1 000000000508ea20  188c  80   000000012012c538
1660 0000000004f13608            1         1 00000000050892f0  32fc  65   00000001df800940
1682 00000000051608a0            1         1 000000000508c740  1d58  74   00000001bfa03d20
1746 0000000004f14e88            1         1 0000000008f1c9e0   e88 104   000000015f6fcd10
1883 0000000004f19938            1         1 0000000005092e90  27c4  46   00000000ff76d2b0
1886 0000000004f1b760            1         1 0000000008f19b60  2dd4  96   000000019fc07030
2036 0000000004f1ae10            1         1 0000000008f1be40  4f58 102   00000001dfcb9da8
2042 0000000004f12e68            1         1 00000000052c8c20  2300 122   000000015f6aaa98
2049 0000000004f1cda0            1         1 00000000052c9d90  1948 126   00000001df6fd688
2153 0000000004f16d88            1         1 0000000005094ba0  3f04  51   00000000ff677eb8
2262 0000000004f13de8            3         1 00000000052ca360   6fc 127   000000011fd7a450
2358 00000000050fc390            1         1 0000000009221280  3ca0 130   0000000120055ca0
-----------------------------
Total           2553
CCW             3
RCW             2
ComClassFactory 0
Free            1212

Answer 1

SyncBlock 000000019f1ec5d8 是没有所有者的那个。也是唯一一个具有偶数 MonitorHeld 计数的。由于 MonitorHeld 递增 with 1 for the owner and 2 for each waiter我的猜测是，这是在转储被采用之前释放的资源，并且尚未授予新所有者。不公平的资源在释放时向所有服务员发出信号，服务员急于获取它(这种不公平的行为避免了护航锁)。直到服务员被调度和运行，并且第一个服务员抢到资源，才会有所有者。

另见 A high waiter count on a free critical section may indicate a lock convoy :

If you're debugging a performance problem in your application, you may run across a critical section in a very strange state: A lot of threads are waiting for it, but nobody owns it!

...

This state means that the previous owner of the critical section has just exited it and signalled a waiting thread to take it, but that thread hasn't yet gotten a chance to run yet