[Vm-dev] Image freeze because handleTimerEvent and Seaside process gone?!

[Andreas Raab]

At a guess, I'd say it's either one of two issues:

1) Your STOP/CONT handling. This sounds suspicious and it could affect 
the timer handling. I'm assuming that the issue happens after receiving 
the CONT signal, no? If you can, you might want to a) make sure that you 
only get the STOP signal when the VM is in ioRelinquish() and not (for 
example) currently executing the delay process and b) consider to dump 
the call stacks whenever the VM gets the CONT signal to see what the 
status is.

2) Some set of incomplete process/delay/semaphore changes in Pharo. One 
of the problems with processes and delays is that this part of the 
system reacts very badly to random "cleaning". I.e., changing "foo == 
nil" to "foo isNil" can have dramatic effects (since it introduces a 
suspension point) with just the kind of weird issue you're seeing.

With regards to these processes not being printed, that's a side effect 
of how printAllStacks gathers the processes - it will not print 
suspended processes which explains why the UI process doesn't print and 
most likely handleTimerEvent is suspended in a debugger.

Depending on how important this issue is you can also try to dissect the 
object memory itself. If you call writeImageFile (or is it 
writeImageFileIO?) from gdb it will dump the .image file and you can use 
the simulator to look at it more closely. Most likely you'll be able to 
find the processes and look at their stacks.

Cheers,
   - Andreas

On 12/6/2010 2:55 AM, Adrian Lienhard wrote:
>
> Hi all,
>
> We've been experiencing an "interesting" problem: the image freezes and does not response to HTTP requests anymore after it has been running for days.
>
> Here some basic information about our setup:
>
> Squeak VM 4.0.3-2202 compiled with gcc 4.3.2
> PharoCore 1.1
> OS Debian Lenny amd64 (CPUs are 4 Intel Xeon E5530 2.40GHz)
>
> - We have never seen the problem with the Squeak VM 3.9-9 and Squeak 3.9 on the identical machine and with the same application source (modulo some adaptations to make it run on Pharo).
> - We run the VM with -mmap 512m -vm-sound-null -vm-display-null, and the UI process is suspended (Project uiProcess suspend)
> - VM does not hog the CPU and memory usage is normal
> - The meantime between failure is several weeks and we haven't managed to reproduce the problem
> - The application mainly serves HTTP requests. When the image does not receive requests for some time we send it a STOP signal, when a request comes in it is sent a CONT signal.
> - lsof shows
> 	TCP *:9093 (LISTEN)
> 	TCP server:9093->server:46930 (CLOSE_WAIT)
>
> Below is a GDB backtrace and the Smalltalk stacks from an image that was frozen (the VM had been running for almost 100 hours):
>
> =============================================================
> (gdb) bt
> #0  0x08072020 in ?? ()
> #1<signal handler called>
> #2  0xb766f5e0 in malloc () from /lib/libc.so.6
> #3<function called from gdb>
> #4  0xb76c50c8 in select () from /lib/libc.so.6
> #5  0x08071063 in aioPoll ()
> #6  0xb778bb8d in ?? () from /usr/lib/squeak/4.0.3-2202//so.vm-display-null
> #7  0x000003e8 in ?? ()
> #8  0x997b5a34 in ?? ()
> #9  0xbfe7cb28 in ?? ()
> #10 0x08074575 in ioRelinquishProcessorForMicroseconds ()
> Backtrace stopped: frame did not save the PC
>
> (gdb) call printCallStack()
> -1719969228>idleProcess
> -1719969320>startUp
> -1740134028 BlockClosure>newProcess
> $3 = -1755344892
>
> (gdb) call (int) printAllStacks()
> Process
> -1719969228>idleProcess
> -1719969320>startUp
> -1740134028 BlockClosure>newProcess
>
> Process
> -1740113860>finalizationProcess
> -1740113952>restartFinalizationProcess
> -1740113532 BlockClosure>newProcess
>
> Process
> -1740134424 SmalltalkImage>lowSpaceWatcher
> -1740134516 SmalltalkImage>installLowSpaceWatcher
> -1740134300 BlockClosure>newProcess
>
> Process
> -1719451488 Delay>wait
> -1719451580 BlockClosure>ifCurtailed:
> -1719451704 Delay>wait
> -1719451796 InputEventPollingFetcher>waitForInput
> -1740126940 InputEventFetcher>eventLoop
> -1740127032 InputEventFetcher>installEventLoop
> -1740126816 BlockClosure>newProcess
>
> Process
> -1719557780 UnixOSProcessAccessor>grimReaperProcess
> -1740113624 BlockClosure>repeat
> -1740113716 UnixOSProcessAccessor>grimReaperProcess
> -1740117340 BlockClosure>newProcess
>
> [omitted many newlines between output above]
> =============================================================
>
> What is striking from the above process listing is that two processes are missing: the handleTimerEvent process and the Seaside process (that is, the TCP listener loop). How comes these processes vanished?
>
> This may be related to Pharo or to the Squeak VM.
>
> Has anybody else seen this problem? Any idea how to debug/fix this issue is very much appreciated!
>
> Cheers,
> Adrian
>
>
> CCed to pharo-dev since this may be related to Pharo; please respond on the squeak-vm list
>
>
>