This article describes an issue in which a high CPU usage occurs for 12 seconds on a multiple-network-adapters computer that's running Windows Server 2012 R2 or Windows Server 2012. A hotfix is available to fix this issue. Before you install this hotfix, see the Prerequisites section.

Symptoms

On a computer that has multiple network adapters, the CPU usage increases to 100 percent for about 12 seconds when the system tries to resolve NetBIOS names by using the LmHosts file. On a multi-core or multiprocessor system, the CPU usage on one CPU increases to 100 percent for about 12 seconds, and the CPU usage on other CPUs is also abnormally high. This situation usually occurs when many concurrent accesses to some shared resources occur and may occur repeatedly.

Cause

This problem occurs because of a race condition. An endless loop may occur in the following scenario:

  • Multiple network name resolutions are performed on each adapter.

  • Some name resolutions are canceled after one of them succeeds.

  • A lookup into the LmHosts file is performed.

In this scenario, the lookup enters a dead loop that can only be ended by a time-out. This time-out is configured in a registry entry. By default, this time-out is set to 12 seconds.

Resolution

To fix this issue, we've released a hotfix for Windows Server 2012 R2 or Windows Server 2012. Additionally, we've also released a hotfix for Windows 8.1 or Windows 8.

Hotfix information

Important If you install a language pack after you install this hotfix, you must reinstall this hotfix. Therefore, we recommend that you install any language packs that you need before you install this hotfix. For more information, see Add language packs to Windows.


A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that's described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there's a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section doesn't appear, submit a request to Microsoft Customer Service and Support to get the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that don't qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website:

http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you don't see your language, it's because a hotfix isn't available for that language.

Prerequisites

To apply this hotfix, install update 2919355 in Windows 8.1 or Windows Server 2012 R2.

There's no prerequisite for Windows 8 or Windows Server 2012.

Registry information

To use the hotfix in this package, you don't have to make any changes to the registry.

Restart requirement

You may have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix doesn't replace a previously released hotfix.

The global version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Windows 8.1 and Windows Server 2012 R2 file information and notes

Important Windows 8.1 hotfixes and Windows Server 2012 R2 hotfixes are included in the same packages. However, hotfixes on the Hotfix Request page are listed under both operating systems. To request the hotfix package that applies to one or both operating systems, select the hotfix that's listed under "Windows 8.1/Windows Server 2012 R2" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

  • The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:

    Version

    Product

    Milestone

    Service branch

    6.3.960 0.18 xxx

    Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2

    RTM

    GDR

  • GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.

  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information" section. MUM, MANIFEST, and the associated security catalog (.cat) files, are very important to maintain the state of the updated components. The security catalog files, for which the attributes aren't listed, are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows 8.1

File name

File version

File size

Date

Time

Platform

Netbt.sys

6.3.9600.18053

214,528

11-Sep-2015

13:51

x86

For all supported x64-based versions of Windows 8.1 and of Windows Server 2012 R2

File name

File version

File size

Date

Time

Platform

Netbt.sys

6.3.9600.18053

283,136

11-Sep-2015

14:09

x64

For all supported Windows RT 8.1

File name

File version

File size

Date

Time

Platform

Netbt.sys

6.3.9600.18053

203,264

11-Sep-2015

13:58

Not applicable

Windows 8 and Windows Server 2012 file information and notes

Important Windows 8 hotfixes and Windows Server 2012 hotfixes are included in the same packages. However, hotfixes on the Hotfix Request page are listed under both operating systems. To request the hotfix package that applies to one or both operating systems, select the hotfix that's listed under "Windows 8/Windows Server 2012" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

  • The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:

    Version

    Product

    Milestone

    Service branch

    6.2.920 0.21xxx

    Windows 8 and Windows Server 2012

    RTM

    LDR

  • GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.

  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information" section. MUM, MANIFEST, and the associated security catalog (.cat) files, are very important to maintain the state of the updated components. The security catalog files, for which the attributes aren't listed, are signed with a Microsoft digital signature.


For all supported x86-based versions of Windows 8

File name

File version

File size

Date

Time

Platform

Netbt.sys

6.2.9200.21630

254,464

11-Sep-2015

13:17

x86

For all supported x64-based versions of Windows 8 and of Windows Server 2012

File name

File version

File size

Date

Time

Platform

Netbt.sys

6.2.9200.21630

331,264

11-Sep-2015

13:16

x64

Additional file information

Additional file information for Windows 8.1 and for Windows Server 2012 R2

Additional files for all supported x86-based versions of Windows 8.1

File property

Value

File name

X86_3686f603707a95f35ad5ae79b7625118_31bf3856ad364e35_6.3.9600.18053_none_5643e227a6e0d617.manifest

File version

Not applicable

File size

700

Date (UTC)

11-Sep-2015

Time (UTC)

21:38

Platform

Not applicable

File name

X86_microsoft-windows-netbt-minwin_31bf3856ad364e35_6.3.9600.18053_none_806b8200f36229bf.manifest

File version

Not applicable

File size

5,300

Date (UTC)

11-Sep-2015

Time (UTC)

14:50

Platform

Not applicable

Additional files for all supported x64-based versions of Windows 8.1 and of Windows Server 2012 R2

File property

Value

File name

Amd64_8a3144df237cc5aaf75dd0eefab982d8_31bf3856ad364e35_6.3.9600.18053_none_8b3a4172b770a76a.manifest

File version

Not applicable

File size

704

Date (UTC)

11-Sep-2015

Time (UTC)

21:39

Platform

Not applicable

File name

Amd64_microsoft-windows-netbt-minwin_31bf3856ad364e35_6.3.9600.18053_none_dc8a1d84abbf9af5.manifest

File version

Not applicable

File size

5,302

Date (UTC)

11-Sep-2015

Time (UTC)

15:16

Platform

Not applicable

Additional files for all supported Windows RT 8.1

File property

Value

File name

Arm_7fb4604b97ae63b9fce751ea99dcdc2e_31bf3856ad364e35_6.3.9600.18053_none_7d37c374ca04845f.manifest

File version

Not applicable

File size

700

Date (UTC)

11-Sep-2015

Time (UTC)

21:38

Platform

Not applicable

File name

Arm_microsoft-windows-netbt-minwin_31bf3856ad364e35_6.3.9600.18053_none_806df458f35f4885.manifest

File version

Not applicable

File size

5,300

Date (UTC)

11-Sep-2015

Time (UTC)

14:41

Platform

Not applicable

Additional file information for Windows 8 and for Windows Server 2012

Additional files for all supported x86-based versions of Windows 8

File property

Value

File name

X86_7a043d6af8424c64736f286f03803a46_31bf3856ad364e35_6.2.9200.21630_none_291fe3a17275c45e.manifest

File version

Not applicable

File size

700

Date (UTC)

11-Sep-2015

Time (UTC)

20:45

Platform

Not applicable

File name

X86_microsoft-windows-netbt-minwin_31bf3856ad364e35_6.2.9200.21630_none_e9132565c23f4d47.manifest

File version

Not applicable

File size

5,300

Date (UTC)

11-Sep-2015

Time (UTC)

14:00

Platform

Not applicable

Additional files for all supported x64-based versions of Windows 8 and of Windows Server 2012

File property

Value

File name

Amd64_81e7b353be5320aefdfb39077871f037_31bf3856ad364e35_6.2.9200.21630_none_96c123e5f033f2e5.manifest

File version

Not applicable

File size

704

Date (UTC)

11-Sep-2015

Time (UTC)

20:45

Platform

Not applicable

File name

Amd64_microsoft-windows-netbt-minwin_31bf3856ad364e35_6.2.9200.21630_none_4531c0e97a9cbe7d.manifest

File version

Not applicable

File size

5,302

Date (UTC)

11-Sep-2015

Time (UTC)

15:00

Platform

Not applicable



File Information

The English (United States) version of this software update installs files that have the attributes that are listed in the following tables. The dates and times for these files are listed in Coordinated Universal Time (UTC). Be aware that dates and times for these files on your local computer are displayed in your local time and with your current daylight saving time bias. The dates and times may also change when you perform certain operations on the files.

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