Hanging process. C/C++ function to get process information.

[Miguel Sanchez_2]

We have a C++ program running on Open VMS 7.1.
We start several instances of the program (>20). The program is connected to a message bus to get requests and control commands like "exit".
Some times, when we send an "exit" command some of the instances hang.
I have added additional logs to the program to get a clue where the process is hanging.
The logs show that the main() function runs until the last line in code ("return").
What could be the cause for that.
I would like to log the process information just before "return" in main() hopping to get an idea on what the process is doing.
How can I get the process information?

Thanks,
Miguel

[Antoniov.]

Miguel,
welcome to vms forum!

You posted too little informazions for helping you. I hint you checking for return code status.
I guess you have one or both troubles:
a) Your software writes using bad pointer but inside its allocation space; in this case your application doesn't get Invalid Allocation Error when which's using pointer but when exits;
b) On exit your application executes some function that's use a bad pointer.

About return, AFAIK on main function it's better use exit() but application can work with return too.

Antonio Vigliotti

[Ian Miller.]

what state is the process in when it is not responding?

[Miguel Sanchez_2]

Thanks Antoniov and Ian for your reply,

I should say that I am not an VMS expert. I do the development on UNIX and than port the program to VMS.
Please, let me know what kind of information you need to help me.

Is there a possibility to get more proccess information before exiting the main function?
For example, I think it could be useful to write a proccess dump (stack dump) like after a crash. How can I do that?.
Do I have a chance to know if the application ist using bad pointers?

Ian:
How can I get the proccess state you are asking for?
Below is the process information provided by "show proccess/all/id=xxxx":

24-JUN-2005 09:13:06.37 User: AA_XX Process ID: 49C32B1C
Node: AAA Process name: "WSM_BGH0LW_P_1"

Terminal:
User Identifier: [BBBUSR,AA_XX]
Base priority: 4
Default file spec: Not available
Number of Kthreads: 2

Devices allocated: BG411:

Process Quotas:
Account name:
CPU limit: Infinite Direct I/O limit: 960
Buffered I/O byte count quota: 97440 Buffered I/O limit: 2688
Timer queue entry quota: 199 Open file quota: 294
Paging file quota: 966096 Subprocess quota: 50
Default page fault cluster: 64 AST quota: 499
Enqueue quota: 2999 Shared file limit: 0
Max detached processes: 0 Max active jobs: 0

Accounting information:
Buffered I/O count: 3756229 Peak working set size: 31792
Direct I/O count: 889650 Peak virtual size: 202976
Page faults: 2711 Mounted volumes: 0
Images activated: 17
Elapsed CPU time: 0 00:53:46.39
Connect time: 3 23:51:21.52

Authorized privileges:
GROUP NETMBX OPER SYSLCK TMPMBX

Process privileges:
GROUP may affect other processes in same group
NETMBX may create network device
SYSLCK may lock system wide resources
TMPMBX may create temporary mailbox

Process rights:
AA_XX resource

System rights:
SYS$NODE_AAA

Auto-unshelve: on

Image Dump: off

Soft CPU Affinity: off

Parse Style: Traditional

Home RAD: 0

There is 1 process in this job:

WSM_BGH0LW_P_1 (*)

Thanks,
Miguel

[Volker Halle]

Miguel,

you can simply obtain the state of your process with SHOW SYSTEM/PROC=

As you are running an old version of OpenVMS, you cannot use the SET PROC/DUMP=NOW command to force a process dump, when your process is hung.

But you can look at the hung process with SDA

$ ANAL/SYS
SDA> SET PROC/IND=
SDA> SHOW PROC
SDA> SHOW PROC/LOCK
SDA> SHOW PROC/CHAN
SDA> CLUE CALL
SDA> SHOW STACK

The information obtained by SDA needs to be reviewed by someone experienced with OpenVMS internals.

Volker.

[Robert Gezelter]

Miguel,

Which log are you looking at?

- Bob Gezelter, http://www.rlgsc.com

[Miguel Sanchez_2]

Thanks Volker for the commands,

Attached is the information provided by SDA for two hanging processes.

Thanks,
Miguel

[Volker Halle]

Miguel,

o.k. - so the program 'hangs' in PTRHEADs (indicated by the process state of HIBernate and PTRHEAD$RTL as the caller of SYS$HIBER_C). You now need to use the SDA PTHREAD extension to look at the PTHREAD status of the process:

SDA> SET PROC/IND=
SDA> pthread help ! gives some help about options

SDA> pthread t -1a ! show thread state

You are running OpenVMS Alpha V7.2-2. Make sure you have all available patches installed. There is a VMS722_PTRHEAD-V0100 patch (among many others).

But before installing patches, start with looking at the thread states of your application first, maybe you can find the problem in the application...

Volker.

[Miguel Sanchez_2]

Hello Volker,

Attached is the threads information provided by SDA.

Thanks,
Miguel

[Volker Halle]

Miguel,

thanks for the info. The situation is the same in both hanging processes:

The exit-handling thread is blocked on a mutex

SDA> pthread mutexes

will show the mutexes. To see which code is running in the exit-handling thread, one could try:

SDA> pthread stack

and then examine the current stack of thread -4

SDA> SHOW STACK ;60

If you can locate a frame pointer, try SDA> SHOW CALL , otherwise just provide the output from the commands above.

Please be aware, that this might become a lengthy troubleshooting effort. Did you check, whether you have the most recent PTHREAD patches installed ?

Volker.