Monday, August 10, 2015

Weird Sleep/Wakeup problems in Windows 10 preview laptop

My Lenovo X1 Carbon laptop experienced some weird problems earlier in the Windows 10 preview cycle; it would crash after a couple of sleep/wakeup cycles, and reboot afterwards. I was surprised that I was the only one experiencing that problem internally, especially since all the preview flighting was going smoothly. But when the problem persisted after a couple of internal upgrades, I decided to dig deeper and figure out what was going on.

When Windows crashes, it writes a memory dump to the C:\Windows\memory.dmp file, and you can examine the contents of that file, and figure out reasons for the crash through windows kernel debugger (Windbg). Windbg is available for download either separately or as part of the WDK. Once it is downloaded, the process is easy. First run Windbg with elevated permissions (Run as Administrator), and open the memory dump file (CTRL+D). If the debugger complains about the symbols, try to fix them and reload through:
.symfix; .reload

You can then look for what caused the crash. In my case, it was a problem with ndis.sys where the network driving was timing out and causing Windows to crash. I am not sure how the network driver got corrupted during my flighting upgrades, but uninstalling the driver (Winkey+X, run device manager, find the adapter, and uninstall) and reinstalling it solved the problem from that time onward.