This shows up as js::EqualStrings in the hang detector, but in every stack trace I looked at (and I looked at 10 or so), it was being called by array_indexOf, which is a more likely culprit. I'm not sure if anything can really be done about this. Some of them had deep stacks, but mostly they looked like this: 0 xul.dll js::EqualStrings js/src/jsstr.cpp:3339 1 xul.dll array_indexOfHelper js/src/jsarray.cpp:3044 2 xul.dll array_indexOf js/src/jsarray.cpp:3065 3 xul.dll js::InvokeKernel js/src/jsinterp.cpp:625 4 xul.dll js_GetMethod js/src/jsobj.cpp:5867 5 xul.dll js::Interpret js/src/jsinterp.cpp:3751 One I saw was during a GC.

js::StrictlyEqual is another much less common signature that has similar stacks that end in array_indexOf. Not necessarily string-related.

array_indexOfHelper contains a JS_CHECK_OPERATION_LIMIT in the central loop. I strongly suspect this is more of DOMOperationCallback failing to stop the script (bug 699974 and 670183).

Ah, that makes sense. It looks like this is a top-ten overall source of "crashes" right now.

GetElement is a fairly uncommon hang, but all instances I found were being called in array_indexOf.

Marking P1 because this is a very common source of hangs. It looks like it could be one of the top 2 or 3 hangs that doesn't involve the file system.

Moving to DOM because that's where the work actually happened. Bug 699974 may have fixed this but we are not sure without data.

This style of hang detector seems to be obsolete, so I think it makes sense to close these hangs, and file new reports for things the new hang detector finds.