Today, we are releasing the February 2020 Preview of Quality Rollup for Windows 10 1909, Windows 10 1903, Windows Server, version 1909 and Windows Server, version 1903.

Quality and Reliability

This release contains the following quality and reliability improvements.

CLR¹

• Addresses an issue with rare crashes or deadlocks that could occur if a GC occurs while another thread is running NGen’ed code which makes the initial call into a static method within the same module where one or more parameter types involve type-forwarded value types.
• Addresses rare crashes that could occur if Server GC is enabled and a GC occurs while another thread is running NGen’ed code which is making the initial call into NGen’ed code in a 2nd module where one or more parameter types involve valuetypes defined in a 3rd module.
• The PAUSE instruction latency increased dramatically on the Intel Skylake processor (documented in “Section 2.2.4 Pause Latency in Skylake Microarchitecture” of the Intel 64 and IA-32 Architectures Optimization Reference Manual). As such places in the runtime that call YieldProcessor (which translates to this instruction) in a loop needed to adjust the number of iterations to call it. GC now takes a scale factor (provided by testing how long the instruction takes and scaling it down) and uses that to adjust the number of iterations so the total time approximates what happened on previous processors. A common symptom is in Server GC where GC spends a much larger percentage in CPU time inclr!SVR::t_join::join and with this change you should see the time go down to the previous percentage.
• Addresses an issue with a crash that could occur in some configurations involving either hot-added CPUs or multi-group machines where per-group CPU count is not consistent across all groups.
• Addresses an issue with a rare crash that can occur during the first call that native code makes into the managed portion of a mixed-mode DLL.

WCF²

• Addresses an issue when using the WCFNetTcp binding. If a client stops responding during the connection handshake, sometimes a service will use the binding receive timeout instead of the open timeout. This update ensures that the correct open timeout is used during the entire handshake.

Workflow²

• Addresses an accessibility issue where text inside a Windows Workflow Foundation Visual Basic Editor would use the wrong colors in high contrast themes.

Winforms

• Addresses an issue with interaction between WPF user control and hosting WinForms app when processing keyboard input.
• Addresses an issue getting accessible objects for PropertyGridView ComboBox property items – adding the verification for item existence and validity.
• Addresses an issue with WinForms ComboBox control reinitialization in AD FS MMC UI.

¹ Common Language Runtime (CLR)
² Windows Communication Foundation (WCF)

Getting the Update

The Preview of Quality Rollup is available via Windows Update, Windows Server Update Services, and Microsoft Update Catalog.

Microsoft Update Catalog

You can get the update via the Microsoft Update Catalog. For Windows 10, NET Framework 4.8 updates are available via Windows Update, Windows Server Update Services, Microsoft Update Catalog. Updates for other versions of .NET Framework are part of the Windows 10 Monthly Cumulative Update.

Note: Customers that rely on Windows Update and Windows Server Update Services will automatically receive the .NET Framework version-specific updates. Advanced system administrators can also take use of the below direct Microsoft Update Catalog download links to .NET Framework-specific updates. Before applying these updates, please ensure that you carefully review the .NET Framework version applicability, to ensure that you only install updates on systems where they apply.

The following table is for Windows 10 and Windows Server 2016+ versions.

Previous Monthly Rollups

The last few .NET Framework Monthly updates are listed below for your convenience:

• February 2020 Security and Quality Rollup
• January 2020 Preview of Quality Rollup
• January 2020 Security and Quality Rollup
• December 2019 Security and Quality Rollup