Cog: Infinite recursion leads to crash
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Cog: Infinite recursion leads to crash
 
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Hello, Eliot. By running some experimental stuff under Cog, Chris get into an infinite resursion, which, instead of showing 'low space' warning leads to VM crash. I am not sure what exactly caused recursion in his code (i hope this just a simple bug, not related to VM). What i found disturbing, that i was able to reproduce crash with simple code (see attachment). The only difference between crash report of mine: Smalltalk stack dump: 0x924088 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion 0x9240ac M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion 0x91e6f8 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion 0x91e71c M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion 0x91e740 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion 0x91e764 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion 0x91e788 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion .... and Chris, that in his case an objects, somehow went outside of a heap: Smalltalk stack dump: 0xbfa31668 M class()> 20181257720x784a27cc is not on the heap 0xbfa31690 M class( class)> 20268642800x78cf7e98 is not on the heap 0xbfa316a8 M class( class)> 20268642800x78cf7e98 is not on the heap 0xbfa316c8 M ()> 20366153080x7964488c is not on the heap 0xbfa316e0 M class> 20129812280x77fba7ec is not on the heap 0xbfa316f8 M > 20135071280x7803ae38 is not on the heap 0xbfa31720 M class( class)> 20268642800x78cf7e98 is not on the heap 0xbfa31738 M class( class)> 20268642800x78cf7e98 is not on the heap 0xbfa31758 M ()> 20366153080x7964488c is not on the heap 0xbfa31770 M class> 20129812280x77fba7ec is not on the heap 0xbfa31788 M > 20135071280x7803ae38 is not on the heap ... I was running under windoze, and were able to watch how vm consuming memory, and somewhere little above 512Mb, it crashing. It is bad, of course, when your own code going mad, but it should not be the reason for VM to go mad as well :) -- Best regards, Igor Stasenko AKA sig. |
InfiniteRecursion.st (570 bytes)
Re: Cog: Infinite recursion leads to crash
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Tim Rowledge and I spent a week about 6 years back exploring this issue. It's a fascinating problem to fix, good luck. The problem is that you are allocating a method context , I can't speak to what COG is doing, but obviously memory has to come from somewhere, memory is finite... So allocate a memory context, a few 100 bytes (more or less) frantically... The "flawed" low memory logic wakes up and decides there is a problem. What's the threshold for that? A few 100K? Allocating 100K a second, what maybe 100MB a second via this recursion? Well you get the idea. You've seconds or less to determine what to do. The default is to throw an exception which triggers a dialog, but too late... By the time the dialog gets working the recursive loop has burn thru the final bits of free memory. Also if this task a back ground thread it would still be running. Now a possible fix. (a) You suspend all processes except the one(s) needed to show the emergency memory dialog. This actually isn't hard it just requires a good knownledge of what can or cannot be suspended. I do note in this case you might be able to say. Oh look if that process has a context depth of 10,000 that could be the villain, and or see (a) On 2010-10-20, at 12:15 PM, Igor Stasenko wrote: > Hello, Eliot. > > By running some experimental stuff under Cog, Chris get into an > infinite resursion, > which, instead of showing 'low space' warning leads to VM crash. > > I am not sure what exactly caused recursion in his code (i hope this > just a simple bug, not related to VM). > What i found disturbing, that i was able to reproduce crash with > simple code (see attachment). > > The only difference between crash report of mine: > > Smalltalk stack dump: > 0x924088 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion > 0x9240ac M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion > 0x91e6f8 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion > 0x91e71c M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion > 0x91e740 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion > 0x91e764 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion > 0x91e788 M InfiniteRecursion>deeeep: 292975484: a(n) InfiniteRecursion > .... > > and Chris, that in his case an objects, somehow went outside of a heap: > > > Smalltalk stack dump: > 0xbfa31668 M class()> 20181257720x784a27cc is not on the heap > 0xbfa31690 M class( class)> 20268642800x78cf7e98 is not on the heap > 0xbfa316a8 M class( class)> 20268642800x78cf7e98 is not on the heap > 0xbfa316c8 M ()> 20366153080x7964488c is not on the heap > 0xbfa316e0 M class> 20129812280x77fba7ec is not on the heap > 0xbfa316f8 M > 20135071280x7803ae38 is not on the heap > 0xbfa31720 M class( class)> 20268642800x78cf7e98 is not on the heap > 0xbfa31738 M class( class)> 20268642800x78cf7e98 is not on the heap > 0xbfa31758 M ()> 20366153080x7964488c is not on the heap > 0xbfa31770 M class> 20129812280x77fba7ec is not on the heap > 0xbfa31788 M > 20135071280x7803ae38 is not on the heap > ... > > > I was running under windoze, and were able to watch how vm consuming > memory, and somewhere little above 512Mb, it crashing. > > It is bad, of course, when your own code going mad, but it should not > be the reason for VM to go mad as well :) > > > > -- > Best regards, > Igor Stasenko AKA sig. > <InfiniteRecursion.st> =========================================================================== John M. McIntosh <[hidden email]> Twitter: squeaker68882 Corporate Smalltalk Consulting Ltd. http://www.smalltalkconsulting.com =========================================================================== |
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