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proton-c/src/object/map.c
<https://reviews.apache.org/r/33623/#comment132288>

    These decrefs can trigger finalizers which could indirectly cause more 
entries to be deleted from the map thereby causing the code to become 
reentrant. To make that safe, you want the decrefs to be the last thing you do 
so that all the structural modifications to the entries are complete before 
that can happen.


- Rafael Schloming


On April 28, 2015, 10:57 a.m., Gordon Sim wrote:
> 
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> https://reviews.apache.org/r/33623/
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> (Updated April 28, 2015, 10:57 a.m.)
> 
> 
> Review request for qpid, Alan Conway, Andrew Stitcher, and Rafael Schloming.
> 
> 
> Bugs: PROTON-858
>     https://issues.apache.org/jira/browse/PROTON-858
> 
> 
> Repository: qpid-proton-git
> 
> 
> Description
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> 
> The internal map implementation for proton-c uses coalesced hashing, but the 
> current deletion algorithm does not take account of this. On deletion of 
> entries, the map can lose its ability to locate other entries by key.
> 
> This patch is the simplest possible fix. It frees the deleted entry, makes 
> any previous entry that points to this tha tail of its chain, and then 
> relocates any entries in a chain following the deleted entry. Though I 
> believe this to be correct and safe, it does involve more work on some 
> deletions. The approach can be optimised further, either be reducing the 
> amount of chain that needs relocated, or by marking records as deleted in the 
> first instance and only rehashing later on some criteria.
> 
> (I started off trying to do the latter, but it is more complicated and I 
> still haven't got my patch fully correct. When I get that working I'll post 
> that also. It is a more involved change though, so perhaps we may want to 
> consider this simpler approach for 0.9.1).
> 
> 
> Diffs
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> 
>   proton-c/src/object/map.c 1a758a1 
> 
> Diff: https://reviews.apache.org/r/33623/diff/
> 
> 
> Testing
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> 
> 
> Thanks,
> 
> Gordon Sim
> 
>

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