The strange case of the large LiveKernelReports folder


Some time back, I ran into a bit of a space crunch on the C: drive of my laptop which runs Windows 8.1. On digging a bit, I found a 2GB+ file at C:\Windows\LiveKernelReports\WinsockAFD-20150114-1722.dmp. Now, this was the first time I had seen a folder called LiveKernelReports and definitely the first time that I had seen a dump file with the name WinsockAFD*.dmp.

Important note: if you are not a developer and came here trying to figure out what to do with the files in this folder, please proceed directly to the ‘So What?’ section below.

Inside the Dump File

The first thing I did (of course Smile) was to open up the dump file under the WinDbg debugger. In kernel mode dumps, the !analyze –v command generally gives good analysis results, so I decided to start from there (full output of !analyze is at the end of this post as an Appendix).

Firstly, the bugcheck code was 0x156. If you are a developer, and you have the Windows 8.1 SDK, you will see this file C:\Program Files (x86)\Windows Kits\8.1\Include\shared\bugcodes.h which has the bugcheck names. 0x156 is WINSOCK_DETECTED_HUNG_CLOSESOCKET_LIVEDUMP.

Second, this bugcheck, unlike most of the ones we know, did not ‘crash’ or ‘blue screen’ the system.

Live Kernel Dumps

All of this is great, but what’s really happening here? How come I got kernel dumps without the system ‘crashing’? Well, the answer is that in Windows 8.1 the Windows development team added some great reliability diagnostics in the form of ‘Live Kernel Dump Reporting’. With this feature, certain Windows components can request a ‘live dump’ to be gathered. In my above case, both a minidump (~ 278KB) and a ‘larger’ dump (~ 2GB) were gathered when the AFD (Ancillary Function Driver for WinSock) runtime detected that a socket did not close ‘in time’ (see bold sections in the Appendix for more information.)

The Windows Error Reporting feature will then use the minidump to help the Windows development team figure out if this is a ‘trending’ issue, prioritize it and then hopefully fix it if it is due to an issue with Windows. The ‘larger’ dump which I mentioned above is not normally uploaded unless the development team ‘asks’ for it again via the Windows Error Reporting and Action Center mechanisms (to ultimately give the end user control on what gets submitted.)

So What?

That is the million dollar question Smile As an end user, you may be wondering what to do with these types of dump files. The advice I can give you is: if the dump files are causing you to go very low on disk space, you can probably move the dump file off to cheaper storage, like an external HDD. BUT if you are repeatedly getting these dump files, it may be advisable to check for any third party drivers, especially anti-virus products or any other network related software. Sometimes older versions of such software may not ‘play well’ with Windows 8.1 and may be causing a stalled network operation, in turn leading to these dump files.

If you are an IT Pro and seeing these dump files on server class machines and / or on multiple PCs, you may do well to contact our CSS (Customer Service and Support) staff who can guide you further on why these dump files are occurring and what should be the course of action.

In Closing

I hope this helps understand this system folder and why it plays an important role in improving the reliability of Windows. If you are interested in this topic, I highly recommend this talk from Andrew Richards and Graham McIntyre, who are both on the Windows Reliability team. They explain how the OCA / WER mechanism works. Amazing stuff, check it out!

Appendix: !analyze –v output

0: kd> !analyze -v

WINSOCK_DETECTED_HUNG_CLOSESOCKET_LIVEDUMP (156)
Winsock detected a hung transport endpoint close request.
Arguments:

DEFAULT_BUCKET_ID:  WINBLUE_LIVE_KERNEL_DUMP

BUGCHECK_STR:  0x156

STACK_TEXT: 

ffffd001`28e46660 fffff803`bdddd64d : ffffffff`800026bc 00000000`00000000 ffffc001`1f52ec00 00000000`00000000 : nt!DbgkpWerCaptureLiveFullDump+0x11f
ffffd001`28e466c0 fffff801`21b7e3b4 : 00000000`00000001 ffffd001`28e46889 00000000`00000048 ffffe000`3e9afda0 : nt!DbgkWerCaptureLiveKernelDump+0x1cd
ffffd001`28e46710 fffff801`21b7b4ff : ffffe000`3e9afda0 00000000`0000afd2 ffffe000`3e9afd00 00000000`00000002 : afd!AfdCaptureLiveKernelDumpForHungCloseRequest+0xa8
ffffd001`28e46770 fffff801`21b89cad : ffffe000`3e9afda0 ffffd001`28e46889 00000000`0000afd2 ffffd001`28e46808 : afd!AfdCloseTransportEndpoint+0x64ef
ffffd001`28e467d0 fffff801`21b89674 : 00000000`00000001 ffffe000`42d71010 00000000`00000000 ffffe000`3e9afda0 : afd!AfdCleanupCore+0x14d
ffffd001`28e468f0 fffff803`bdc47349 : ffffe000`42d71010 ffffe000`3d3fd080 00000000`00000000

Comments (1)

  1. Richard says:

    Very good information – thanks for sharing Arvind!

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