Hi guys,
This code reproduces the blockade in fresh 1.4 OneClick (with or without
Transcript window open):
[
(Delay forSeconds: 5) wait.
SmalltalkImage current saveSession.
] forkAt: Processor userBackgroundPriority
Note that fork on default priority does not block while on user
background priority it blocks. It does not always block immediately
(sometimes yes sometimes not) but it after image restart it is always
blocked.
But if you periodically write to Transcript from process on user
background priority, it does not block, even if you heavily browse
around, write to transcript, do manual snapshot:
[ [true] whileTrue:
[(Delay forMilliseconds: 500) wait.
Transcript show: '.tst.']
] forkAt: Processor userBackgroundPriority
So, it seems not only thread-safe Transcript but something with snapshot
(from a background priority, why?) is in play here.
SmalltalkImage>>snapshot:andQuit: , shouldn’t run it on highest priority
to block all other processes during the preparation for snapshot?
Hope this helps a bit more
Janko
Dne 21. 04. 2012 11:48, piše Igor Stasenko:
> So, this is related to thread-safe transcript code..
> which using semaphore to synchronize access to transcript stream.
> I guess what happens is that a semaphore is blocked in another
> process, but for some strange reason never released. This leads to
> situation, that any other process which will attempt to write to
> transcript will be blocked as well.. forever.
Why is input not blocked immediately but after image restart?
More investigation:
1. correction: image blocks in any case after restart, regardless if
there is additional writing to Transcript or not. Snapshot namely writes
to Transcript by itself and this is enough to block.
1. even if Transcript is closed the image blocks after restart
This simulated snapshot from the background does NOT block after restart:
[
(Delay forSeconds: 5) wait.
SmalltalkImage current saveSession.
] fork
This one also not:
[ | elapsed |
(Delay forSeconds: 5) wait.
elapsed := Time millisecondsToRun:
[SmalltalkImage current saveSession].
Transcript show: ' in ', (elapsed // 1000) printString, 's '.
] forkAt: Processor userBackgroundPriority
>
> 2012/4/21 Janko Mivšek <[email protected]>:
>> Hi guys,
>>
>> It seems that writing to Transcript from background process causes my
>> freeze after restart. And yes, I have Transcript window open.
>>
>> This is a code snippet in question:
>>
>> AIDASite class>>imageSnapshot
>> ...
>> elapsed := Time millisecondsToRun:
>> [SmalltalkImage current saveSession].
>> Transcript show: ' in ', (elapsed // 1000) printString, 's '.
>>
>>
>> If I comment out the last line, snapshot doesn't block the image after
>> restart.
>>
>> This is not necessary 1.4 specific problem, because I noticed similar
>> problem in 1.3 also. Just that on 1.3 input freezes immediately while on
>> 1.4 it freezes after restart.
>>
>> Let me investigate a bit further, what if Transcript window is not open?
>>
>> Best regards
>> Janko
>>
>>
>>
>> Dne 20. 04. 2012 21:42, piše Stéphane Ducasse:
>>> Ok may be nautilus bug. It should be different than janko problem.
>>>
>>> Stef
>>>
>>> On Apr 20, 2012, at 9:39 PM, Sean P. DeNigris wrote:
>>>
>>>>
>>>> Stéphane Ducasse wrote
>>>>>
>>>>> on which os?
>>>>>
>>>>
>>>> Mac Lion 10.7.3
>>>>
>>>> --
>>>> View this message in context:
>>>> http://forum.world.st/Unresponsive-1-4-image-tp4574693p4575049.html
>>>> Sent from the Pharo Smalltalk mailing list archive at Nabble.com.
>>>>
>>>
>>>
>>>
>>
>> --
>> Janko Mivšek
>> Aida/Web
>> Smalltalk Web Application Server
>> http://www.aidaweb.si
>>
>
>
>
--
Janko Mivšek
Aida/Web
Smalltalk Web Application Server
http://www.aidaweb.si
