Racing condition in DataFolder.setSortMode(DataFolder.SortMode.LAST_MODIFIED)?

[Emilian Bold <em...@gmail.com>]

I have a strong suspicion that org-openide-loaders
DataFolder.setSortMode(DataFolder.SortMode.LAST_MODIFIED)
could lead to a racing condition in the sorting and cause something like

https://bz.apache.org/netbeans/show_bug.cgi?id=257997

java.lang.IllegalArgumentException: Comparison method violates its
general contract!
                at java.util.TimSort.mergeHi(TimSort.java:868)
                at java.util.TimSort.mergeAt(TimSort.java:485)
                at java.util.TimSort.mergeForceCollapse(TimSort.java:426)
                at java.util.TimSort.sort(TimSort.java:223)
                at java.util.TimSort.sort(TimSort.java:173)
                at java.util.Arrays.sort(Arrays.java:659)
                at java.util.Collections.sort(Collections.java:217)
                at
org.openide.loaders.FolderList.carefullySort(FolderList.java:600)
                at
org.openide.loaders.FolderList.getObjects(FolderList.java:570)
                at org.openide.loaders.FolderList.access$600(FolderList.java:77)
                at
org.openide.loaders.FolderList$ComparatorTask.run(FolderList.java:1028)

The reason being that the file timestamp might change *while* the list
if being sorted and
break the comparator contract.

(I also suspect that perhaps some DataObject instantiation could
further delay things long enough for a timestamp to be changed but
this is not really required.)

FolderComparator(FolderComparator.LAST_MODIFIED) as used by DataFolder
needs to be looked at perhaps.

I wonder, does the filesystem prevent the timestamp from being changed
during that careful sorting? Or is there some other locking preventing
this? It's a bit of work but I think a test case could be created
reproducing it.

--emi

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