You cannot log on to a Windows Server 2012 server through the console or RDP

Applies to: Windows Server 2012 DatacenterWindows Server 2012 DatacenterWindows Server 2012 Essentials

Symptoms


You can no longer remotely manage or log on to a Windows Server 2012 server by using the console or Remote Desktop Protocol (RDP). Otherwise, the server still functions correctly in other tasks. The problem is indicated by the following symptoms:

  • A large number of threads exist in svchost hosting netsvcs (~500 when the problems starts occurring).
  • The WinHTTP Web Proxy Auto-Discovery (WPAD) Service is in a disabled state.

Cause


This problem occurs if a large number of threads in netsvcs are waiting for the WPAD Service because the service is disabled. The resulting depletion of the thread pool prevents netsvcs from being able to serve other requests.

Resolution


To resolve this problem, enable the WPAD Service.

More Information


The following is an example stack of a blocked netsvcs worker thread:
fffff8027fd1d606 nt!KiSwapContext+0x76(Inline)         nt!KiSwapThread+0xf4fffff8027fd20c6c nt!KiSwapThread+0xf4fffff8027fd1cf0f nt!KeWaitForSingleObject+0x1cffffff802800c29b6 nt!NtWaitForSingleObject+0xb6fffff8027fcf6053 nt!KiSystemServiceCopyEnd+0x13000007fa9e612c2a ntdll!NtWaitForSingleObject+0xa000007fa9b9810ea KERNELBASE!WaitForSingleObjectEx+0x92000007fa966fd39c WINHTTP!InternalDetectAutoProxyUrl+0x5e47c000007fa9669cc9b WINHTTP!WpadDetection+0x116000007fa966eb8b1 WINHTTP!AutoProxyResolver::DoBackgroundDetection+0x159000007fa966eb9be WINHTTP!AutoProxyResolver::BackgroundWpadDetection+0x5a000007fa966eb4e1 WINHTTP!FailFastThreadpoolTimerCallback<&AutoProxyResolver::BackgroundWpadDetection>+0x9000007fa9e61a50a ntdll!TppTimerpExecuteCallback+0xea000007fa9e618842 ntdll!TppWorkerThread+0x604000007fa9bb3167e KERNEL32!BaseThreadInitThunk+0x1a000007fa9e633501 ntdll!RtlUserThreadStart+0x1d