RE: IIS application error ...the memory could not be "read"...

From: Karl Westerholm [MS] (karlwestonline@microsoft.com)
Date: 07/13/02


From: karlwestonline@microsoft.com (Karl Westerholm [MS])
Date: Sat, 13 Jul 2002 02:47:55 GMT


Greetings,

   It sounds like you have some code running in the 'dllhost.exe' process
(one of your websites running in either medium pooled or high-isolated
process) that is either hanging, or access violating on you. (or both)

   The best way to fix this sort of an issue is to install a debugger to
catch the problem happening and then analyze the resulting dump file. This
link is to the standard IIS4 & IIS5 debugging tool: (basically a VB script
wrapped around a debugger)

http://www.microsoft.com/ddk/debugging/installx86.asp

   You would install the tool, insure all of the websites were up & running
with no errors, and then run the tool (from a command-prompt CD'ed into the
dir with 'adplus.vbs', in '<drive>:\program files\debugging tools for
windows' by default) by issuing the command 'adplus -iis -crash'.

   This will cause a debugger (in a cmd-window) to be spawned up & attached
to inetinfo.exe & all dllhost.exe processes currently running. When there
is an exception or an access violation, one or more of these windows will
close (or 'trip') automatically and a <filename>.dmp file will be written
out to the directory.

   Note: If the issue occurs on a website and none of the cmd-windows
trips on its own, then you have experienced an IIS 'hang'. In that case,
HTML will serve fine from the same website that will no longer serve ASP
pages at all. In this case, issue the command 'adplus -iis hang' to trip
the debugger manually.

   Once either of these scnearios has occurred, you would next open up the
.dmp files in windbg.exe, and analyze them to see what the faulting/hanging
thread(s) might look like...and ultimately discover what components/.dlls
might have been the offenders. Unfortunately, unless you are already savvy
at debugging on your own, this is the point at which you might want to open
up a case w/IIS Support for further analysis.

   However, you do mention that the code itself has not changed for several
years & that the servers themselves are new. Since you already suspect a
patch might have caused the issue to appear you might want to check through
the create date of any <drive>:\winnt\$NtUninstallQ######$ directories.

   Each time you install a patch, one of these dirs should be created in
which is stored the older versions of any files that particular patch
replaced. If you are fairly certain the issue began 3 months ago, you
could try uninstalling patches installed at or near that time-frame.

   Of course, you obviously installed those patches for a reason and it may
*not* be a good idea to uninstall them if this will cause a particular
behavior/bug to recur and cause still *more* problems. In particular, I
would *never* recommend uninstalling any security-related patches. (except
perhaps on an internal server you use exclusively for testing purposes)

  One other step that may be worth taking is to see if the websites that
become unresponsive (ASP does not serve, HTML still does) are doing so not
becuase they have hung, per se, but are in reality just starved for ASP
threads. Often this may not be associated with any high CPU-usage, and you
can get a good hint it is occurring if (in performance monitor) the ASP
object/'requests queued' counter is consistently growing at the same time
the ASP/'requests executing' counter hits a plateau & does not decline.

   That is a topic all its own, however you may find this KB article useful
since you reference database code as being in use:

http://support.microsoft.com/default.aspx?scid=kb;EN-US;q258939

   At least if you do open a support case and it is determined that the
crash is due to a bug in our .dlls then that case would not be charged once
it was resolved and closed. Of course, if it was discovered that custom
code or 3rd-party .dlls were at fault it would be charged.

     Hope this helps,

         -->Karl

“Please do not send email directly to this alias. This is our online
account name for newsgroup participation only.”

This posting is provided “AS IS” with no warranties, and confers no rights.
You assume all risk for your use. © 2001 Microsoft Corporation. All rights
reserved.

--------------------
| Newsgroups: microsoft.public.inetserver.iis.security
| Subject: IIS application error ...the memory could not be "read"...
| From: David <blue.s@removethisbitplease.ukonline.co.uk>
|
| I've got 3 Win2k/IIS 5 servers, all running asp applications from MS SQL
7,
| patched up to date and running a total of 10 websites across the servers.
|
| The problem I have is the asp applications often go down for seemingly no
| reason. The CPU isn't high, the memory usage isn't silly.
|
| They are all running in isolated processes, so often when one goes down,
it
| doesn't affect the others. The main symptom is that asp stops being
| processed, but static html pages and images are served without problem.
| Dllhost for the process isn't running at high CPU usage or memory either.
|
| The event logs usually leaves no trace, except occasionally reporting
that
| performance logs can't be read/written.
|
| I'm convinced this is related to a separate issue which happens on a less
| often basis; the whole server shuts down with the error below in the
event
| log:
|
| ---------------------------------
| Event Type: Information
| Event Source: Application Popup
| Event Category: None
| Event ID: 26
| Date: 7/12/2002
| Time: 9:15:41 PM
| User: N/A
| Computer: TIGER
| Description:
| Application popup: dllhost.exe - Application Error : The instruction at
| "0x77f8765f" referenced memory at "0x07587000". The memory could not be
| "read".
|
| Click on OK to terminate the program
| ---------------------------------
|
| I get this alot on my workstation too, but previously thought it was a
| hardware fault or software issue. This error has only recently started
| occuring (last 3 months)
|
| However with it happening on 3 brand new webservers (Dell poweredge 2550)
| it's not hardware.
|
| It's also on a website that the code has run on perfectly for 2 years,
the
| code hasn't changed, and it is minimal complexity (read one record - url0
| from small database table and redirect to this url) so it's probably not
| the code.
|
| This leaves the possibility of a hotfix that has broken something, or at
| least has started reporting errors that previously were not reported.
|
| Has anyone else had the same experience, and more importantly found a way
| to trace and fix it?
|
| David
|



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