In this case I was looking for PREEMPTIVE_COM_RELEASE, and sys.dm_xe_map_values tells me that on my 2014 RTM instance it has an index of 01d4 hexadecimal. Crazy as it sounds, I’m going to do a simple search through the code to look for places that magic number is used. As a two-byte (word) pattern we’ll get lots of false positives, but fortunately wait types are internally doublewords, with only one bit set in the high-order word. In other words, we’re going to look for the pattern 000101d4, 000201d4, 000401d4 and so forth up to 800001d4. Ignore the meaning of when which bit is going to be set; with only sixteen permutations, it’s quick enough to try them all.
Let’s focus on sqllang as the likely source – the below would apply to any other module too.
This post reminds me that my debugger skills aren’t very good.