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August 11, 2020

War Stories: dwm.exe APPCRASH Insider Feedback

Right now, I find myself in an interesting situation. I’m better equipped than I’ve ever been before to give Insider feedback on recent builds. Why? Because I have 2 nearly identical laptops –both Lenovo X380 Yoga PCs — one running the Insider Release Preview (Build 18363.449), and the other running Insider Fast Ring (Build 19013.1000). Except for the SSD — one machine has a Toshiba OEM drive (KXG5AZNV1T02), the other a Samsung OEM drive (MSVLB1T0HALR-00L7), both 1 TB in size — the two machines have exactly the same hardware all the way ’round. Thus, when my Fast Ring PC started crashing recently and repeatedly on the built-in Desktop Windows Manager (dwm.exe), I was in a great position to let MS know that something in the build MUST be problematic.Take a look at this Reliability Monitor output from October 27, which shows 18 APPCRASH reports for wdm.exe. 9 cluster around 1:58 PM that day, and 9 more around 4:03 PM that same day.

dwm.exe APPCRASH Insider Feedback.Oct27

With two nearly identical machines, each running Win10, when the Insider Fast Ring release starts acting up, I can be pretty sure something in that Fast Ring Build is causing the crashes.
[Click Image for full-sized view.]

Reporting dwm.exe APPcrash Insider Feedback to FB Hub

I’d actually seen similar behavior from the preceding Build 19008 as well, and on the initial release of 19013.1 to boot. Each time the crashes occurred in groups of 9 clustered around a specific time. Each time, I’d also left the machine idle on a Remote Desktop session into the Fast Ring machine, while working on my production desktop. Thus, I had something useful to tell the folks at MS about these errors:

+ The type of machine involved (Lenovo X380, i7-8650U, 16 GB RAM, etc.)
+ The Build numbers affected  19008, 19013 including the .1 initial release and the .1000 CU
+ The runtime circumstances: an idle RDP session from the affected laptop to another PC
+ The clustering of 9 crashes around a specific time seems to indicate the RDP session failed and was trying to restart

So that’s exactly what I did. Hopefully, it will make a difference. I’ve also pretty much proved to myself that there’s a connection between leaving an RDP session open and the dwm.exe crash. If I close my RDP session before I walk away from the Lenovo X380 Yoga, it doesn’t crash anymore and keeps running just fine.

Author: Ed Tittel

Ed Tittel is a 30-plus-year computer industry veteran. He’s a Princeton and multiple University of Texas graduate who’s worked in IT since 1981 when he started his first programming job. Over the past three decades he’s also worked as a manager, technical evangelist, consultant, trainer, and an expert witness. See his professional bio for all the details.

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