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Operating System - OpenVMS
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OpenVMS crash

 
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Stehlik Tomas
Occasional Contributor

OpenVMS crash

Hi all,

I have never seen OpenVMS crash up to now when I run some multithreaded tasks using OmniORB 4.1.3 and SqLite 3.5.7 on fully patched (Update 1000) OpenVMS IA64 8.3.

Application runs fine several hours or even day when system crash.

In SYS$ERRORLOG:CLUE$*.LIS is all the times:

Bugcheck Type: XQPERR, Error detected by file system XQP

Failing Instruction:
UNHOOK_BFRL_C+00550: break.m 100002

I had found minimum privileges to be able to run it (NETMBX , PRMMBX, OPER, READALL) but system crash the same way.

SqLite DB file is exposed over SAMBA V1.1-1 share but system crash when nobody read it.

Can somebody tell me how to interpret such CLUE?
10 REPLIES
Shilpa K
Valued Contributor

Re: OpenVMS crash

Hi Stehlik,

In the clue crash output, I see these lines:

R8 = 00000000.00002124 %SYSTEM-F-IVLOCKID, invalid lock ID
.
.
R19 = FFFFFFFF.8077DC60 SYS$DEQ_C+00060

I wonder if some lock was being dequeued at the time of system crash and if the lockid was invalid as indicated by the status above.

It appears to me that this problem requires a detailed analysis of the system crash to find the actual cause. You may want to log a call with HP support so that they can analyse the dump file.

Regards,
Shilpa
Robert Gezelter
Honored Contributor

Re: OpenVMS crash

Stehlik,

Concur. Call support, and be prepared to send them the dump file.

- Bob Gezelter, http://www.rlgsc.com
Stehlik Tomas
Occasional Contributor

Re: OpenVMS crash

Hi all,

OK I will try to contact HP support.

Just one question - can unprivileged task cause system crash?

Tomas

Re: OpenVMS crash

>can unprivileged task cause system crash?

Ideally, no. But they can cause conditions that cause a buggy kernel to crash.
Shilpa K
Valued Contributor

Re: OpenVMS crash

Hi Stehlik,

As you say you are running CIFS on this system, just curious to know if there were any SMBD process crash on this system in the recent past. Could you please check if there are any dump files in the directory samba$root:[var.cores...]? Also, could you please check if there is any ACCVIO trace-back information in the log files, samba$root:[var]samba$root:[var]SAMBA$SMBD_STARTUP.LOG;*?

Thanks,
Shilpa
Stehlik Tomas
Occasional Contributor

Re: OpenVMS crash

I had search through

$ sea SAMBA$ROOT:[000000...]*.log acc

without any results.



Robert Gezelter
Honored Contributor
Solution

Re: OpenVMS crash

Stehlik,

As to your question: Can unprivileged task cause system crash?

Generally, the answer is no. But no system is perfect.

There have been almost no ways in which a non-privileged program can gain access to elevated states and subvert the system. However, if a non-privileged program (or collection of programs) makes a series of requests that expose a latent inconsistency within the system, a crash can ensue.

The XQP is the OpenVMS component that manages disk file structures. What appears to have happened is that the XQP detected an inconsistency in its data structures and initiated a crash, rather than take the risk of a more systemic problem. This behavior is correct.

READALL in particular should be managed with care. It effectively allows the holder to read any file on the disk, bypassing all of the protection mechanisms.

- Bob Gezelter, http://www.rlgsc.com
Volker Halle
Honored Contributor

Re: OpenVMS crash

Thomas,

an XQPERR in F11BXQP.EXE is most likely an OpenVMS XQP problem. Except if some privileged application (e.g. SAMBA/CIFS ?) is playing 'dirty tricks' with F11B$ locks...

You're already running the most recent F11BXQP.EXE available.

What is or was running in the current process at the time of the crash: process name DEX ?

The first attempt to analyze this crash would be to try to find the lock being DEQued. Look at the stack with SDA> CLUE STACK to try to find an address pointing to a LKB (Lock Block).

Volker.
Shilpa K
Valued Contributor

Re: OpenVMS crash

Hi,

For clarification, VMS CIFS being a port of OpenSource Samba, it is heavily dependent upon CRTL routines and runs only in USER mode. Thus by default, it is not a privileged application and it does NOT makes use of F11B$locks or any such.

Regards,
Shilpa
Steve Reece_3
Trusted Contributor

Re: OpenVMS crash

Just because CIFS is running in user mode doesn't mean that everything else around it and everything that it's affecting are in User mode.
If the system takes out a lock that then gets corrupt due to imperfections elsewhere, that can still cause a crash. This is analogous to a double deallocation of memory that would still cause a crash even though the deallocators may be millions of clock cycles apart.

Looking at the whole problem rather than the little bit of it may be necessary.