February 25, 2020-KB4537490 Cumulative Update for .NET Framework 3.5 and 4.7.2 for Windows 10 Version 1809 and Windows Server 2019

Applies to: .NET Framework

The February 25, 2020 update for Windows 10 Version 1809 and Windows Server 2019 includes cumulative reliability improvements in .NET 3.5 and 4.7.2. We recommend that you apply this update as part of your regular maintenance routines. Before you install this update, see the Prerequisites and Restart requirement sections.

Quality and reliability improvements


WCF1

- 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.

CLR2

- 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.


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

Additional information about this update


The following articles contain additional information about this update as it relates to individual product versions.
  • 4538156 Description of the Cumulative Update for .NET Framework 3.5, 4.7.2 and 4.8 for Windows 10 Version 1809 and Windows Server 2019 (KB4538156)

How to obtain and install the update


Install this update

To download and install this update, go to Settings > Update & Security > Windows Update, and then select Check for updates.

To get the standalone package for this update, go to the Microsoft Update Catalog website.

File information

For a list of the files that are provided in this update, download the file information for cumulative update .

Prerequisites

To apply this update, you must have .NET Framework 3.5 or 4.7.2 installed.

Restart requirement

You must restart the computer after you apply this update if any affected files are being used. We recommend that you exit all .NET Framework-based applications before you apply this update.

Update replacement information

This update replaces previously released updates 4538122.

How to obtain help and support for this update