Confirm necessity of uninterruptibleMask_ in ImmDB/VolDB brackets

[nfrisby]

We're currently adopting PR IntersectMBO/ouroboros-network#1453 for Issue IntersectMBO/ouroboros-network#1452 due to time constraints. This Issue is to revisit alternative solutions, with fewer potentially drastic disadvantages.

[nfrisby]

Here's a more complete stack trace -- I had to futz with call stacks and rank2s to get this, and it was generated from a PR 1419 WIP commit, so the line numbers may be off a little. The basic shape is informative, however.

Note the modifyOpenState called from within withOpenState. Also, the streamAfter frame involves ResourceRegistry.allocateEither, which I think is the key exception handler that doesn't get applied in the Issue 1452 repro I used to prepare PR 1453.

CallStack (from HasCallStack):
  modifyOpenState, called at src/Ouroboros/Storage/ImmutableDB/Impl/Iterator.hs:274:32 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ImmutableDB.Impl.Iterator
  withNewIteratorID, called at src/Ouroboros/Storage/ImmutableDB/Impl/Iterator.hs:288:22 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ImmutableDB.Impl.Iterator
  mkIterator, called at src/Ouroboros/Storage/ImmutableDB/Impl/Iterator.hs:184:18 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ImmutableDB.Impl.Iterator
  action, called at src/Ouroboros/Storage/ImmutableDB/Impl/State.hs:308:27 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ImmutableDB.Impl.State
  access, called at src/Ouroboros/Storage/ImmutableDB/Impl/State.hs:261:79 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ImmutableDB.Impl.State
  withOpenState, called at src/Ouroboros/Storage/ImmutableDB/Impl/Iterator.hs:134:5 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ImmutableDB.Impl.Iterator
  streamImpl, called at src/Ouroboros/Storage/ImmutableDB/Impl.hs:228:29 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ImmutableDB.Impl
  streamHeaders_, called at src/Ouroboros/Storage/ImmutableDB/API.hs:236:5 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ImmutableDB.API
  streamHeaders, called at src/Ouroboros/Storage/ChainDB/Impl/ImmDB.hs:531:17 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ChainDB.Impl.ImmDB
  registeredStream, called at src/Ouroboros/Storage/ChainDB/Impl/ImmDB.hs:658:5 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ChainDB.Impl.ImmDB
  streamAfter, called at src/Ouroboros/Storage/ChainDB/Impl/Reader.hs:439:24 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ChainDB.Impl.Reader
  findFirstPointOnChain, called at src/Ouroboros/Storage/ChainDB/Impl/Reader.hs:415:5 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ChainDB.Impl.Reader
  forward, called at src/Ouroboros/Storage/ChainDB/Impl/Reader.hs:160:7 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ChainDB.Impl.Reader
  readerForward_, called at src/Ouroboros/Storage/ChainDB/Impl/Reader.hs:147:64 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ChainDB.Impl.Reader
  readerForward_, called at src/Ouroboros/Storage/ChainDB/API.hs:570:7 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Storage.ChainDB.API
  readerForward, called at src/Ouroboros/Consensus/ChainSyncServer.hs:124:18 in ouroboros-consensus-0.1.0.0-inplace:Ouroboros.Consensus.ChainSyncServer

cc: @edsko @dcoutts @mrBliss

[mrBliss]

@nfrisby I removed withNewIteratorID as part of IntersectMBO/ouroboros-network#1471 (IntersectMBO/ouroboros-network@7f7ba4c). Can you check whether we still need that uninterruptibleMask_ in the ImmutableDB?

Did we ever need it in the VolatileDB or did you just add it for consistency?

[nfrisby]

@nfrisby I removed withNewIteratorID as part of IntersectMBO/ouroboros-network#1471 (7f7ba4c). Can you check whether we still need that uninterruptibleMask_ in the ImmutableDB?

Did we ever need it in the VolatileDB or did you just add it for consistency?

Also, I don't remember if the details overlap, but I wonder if PR IntersectMBO/ouroboros-network#1547 alleviated this at all?

[mrBliss]

Can you verify that is not necessary anymore?

[mrBliss]

I will remove the use of uninterruptibleMask_ in the VolatileDB in IntersectMBO/ouroboros-network#1866. So if something breaks, we'll know why (although I doubt it).