Windows 8 update bug clogs CPUs

Windows 8 update bug clogs CPUs

A new update to Windows 8, Windows RT and Windows Server 2012 is causing performance problems for some users - but there's a cure.

A bug introduced in the latest update for Windows RT, Windows 8 and Windows Server 2012 is reportedly causing performance problems for many users.

Released earlier this week as part of the company's monthly Patch Tuesday update cycle, KB2821895 is designed to update the servicing stack - the portion of the operating system used by Windows Update - to add much-needed improvements. Among the features tweaked or added by the update are the ability to install previously downloaded updates without an active internet connection, a reduction in certain software sizes, and the automatic compression of unused binary files when updates are installed.

While many of the new features are targeted more at tablet users than desktop users, the update was released to all Windows 8, Windows RT and Windows Server 2012 users on Tuesday. Sadly, it soon transpired that there was a problem: with the update installed, users began to report that processes related to the analysis of system files - in particular the TiWorker.exe application, part of the Microsoft System File Checker tool - would take up masses amounts of processor time, locking cores with between 40 and 100 per cent utilisation until failing with an error.

During this time, a logfile - CBS.log - is seen to rapidly grow with entries that show files being marked as damaged, then unable to be repaired. These files, however, do not appear to be actually damaged, and the system runs as normal - albeit slowly - while the error is occuring.

Not everyone who has installed the patch has reported the problem, and thus far it's not clear what is causing the issue on systems that are affected. With KB2821895 not valid for uninstallation, however, a workaround is needed for those that are suffering from the glitch - and, thankfully, there is one.

According to a member of the German-language Dr. Windows forum, which was one of the first sites to spot the problem, the issue can be solved by running the Deployment Image Servicing and Management (DISM) command below with administrative privileges:

DISM /online /cleanup-image /restorehealth

While this process takes some time, it should prevent the CPU from being overloaded with spurious analysis and error logging. Thus far, Microsoft has not commented on the flaw in the update, nor has it indicated any plans to release a patch of its own for the issue.


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Anakha 14th June 2013, 09:51 Quote
It sounds as though the update is compressing archived update files, but the System File Checker (Which uses those files for rollbacks and the like in case something goes wrong) notices the hashes on the files have changed/don't match what it has on record ('cause they're compressed now), throws an error, and carefully restores the files back to the way they were, at which point the compression system notices they're old and uncompressed and compresses them, and the whole cycle begins anew.
Chances are, the patch to the SFC service to enable it to read the compressed files hasn't applied properly, or the SFC service hasn't been restarted (so the in-memory version doesn't have the patch applied). It could also be related to permissions and/or UAC issues (If the compression service and the SFC service are running as different users with different permissions, it could stop one or the other from being able to read/write the files).
The DISM command listed there essentially throws away SFC's list of system files and their hashes, forcing it to start again from scratch and accept the hashes of the (now compressed) files as good.
Of course, this is all speculation on my part, but speaking as a programmer it's the kind of corner-case that can easily turn up if even one little step goes awry.
Corky42 14th June 2013, 10:06 Quote
Is it only a recent thing that Microsoft seem to be botching updates and not bothering to patch other security flaws such as the one reported and published by Tavis Ormandy.

It is worrying when taken in context with providing intelligence agencies with information about bugs before it publicly releases a fix :|
Doctor Hades 14th June 2013, 16:10 Quote
I had an issue occur on Wednesday after I'd installed 13 Windows Updates where sfc /scannow reported hundreds of errors when I reviewed the CBS.log. I was concerned because I'd just installed a clean copy of Windows 8 Pro on my new i7-4770K build so it didn't make sense that there'd be so many errors unless my SSD was faulty. Even though I subsequently fixed it by running DISM.exe, as suggested in the article, thanks to a fellow forumer's advice, I never did find out what caused it... until now.

Microsoft really should do more testing IMO; it seems more and more issues are cropping up from these updates which are supposed to FIX them not CREATE new ones!!!
koola 15th June 2013, 02:20 Quote
It seems Microsoft has never heard of or done regression testing. Needs a better QA team me thinks.
DC74 16th June 2013, 20:56 Quote
Koola, they've needed that for a number of years, I've lost count of how many updates MS have released that have caused systems to hang or not boot correctly, when previously they have been running fine, resulting in either reinstallation or rollback. I think cutting QA testing in a lot of big companies is a big mistake and pretty much unforgivable for a company of Microsoft's stature.
schmidtbag 20th June 2013, 14:42 Quote
Originally Posted by koola
It seems Microsoft has never heard of or done regression testing. Needs a better QA team me thinks.

Agreed. It seems updates to Windows break more often than the updates of cutting-edge distros of Linux. Also, it seems Windows updates more often take up disk space than they free. Their patches seem to be like trying to fix a pipe leak with duct tape, where if they see a little water drip, they just wrap more tape around it. The fix might work but it's not the best approach.
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