This PR is fixing deadlock for #8918
It avoids some recursive calls on light_sync by making state check optional for Informant.
The current behavior is to display the information when informant checks if block is major version.
This change a bit the informant behavior, but not on most cases.
To remember where and how this kind of deadlock are likely to happen (not seen with Parkinglot deadlock detection because it uses std condvar), I am adding a description of the deadlock.
Also, for the reviewers there may be better solution than modifying the informant.
### Thread1
- ethcore/sync/light_sync/mod.rs
A call to the light handler through any Io (having a loop of rpc query running on like client makes the dead lock way more likely).
At the end of those calls we systematically call `maintain_sync` method.
Here maintain_sync locks `state` (it is the deadlock cause), with a write purpose
`maintain_sync` -> `begin_search` with the state locked open
`begin_search` -> lightcliennt `flush_queue` method
- ethcore/light/src/client/mod.rs
`flush_queue` -> `flush` on queue (HeaderQueue aka VerificationQueue of headers)
- ethcore/src/verification/queue/mod.rs
Condition there is some unverified or verifying content
`flush` wait on a condvar until the queue is empty. The only way to unlock condvar is that worker is empty and unlock it (so thread 2 is Verification worker).
### Thread2
A verification worker at the end of a verify loop (new block).
- ethcore/src/verification/queue/mod.rs
thread loops on `verify` method.
End of loop condition is_ready -> Import the block immediately
calls `set_sync` on QueueSignal which send a BlockVerified ClientIoMessage in inner channel (IoChannel of ClientIoMessage) using `send_sync`
- util/io/src/service_mio.rs
IoChannel `send_sync` method calls all handlers with `message` method; one of the handlers is ImportBlocks IoHandler (with a single inner Client service field)
- ethcore/light/src/client/service.rs
`message` trigger inner method `import_verified`
- core/light/src/client/mod.rs
`import_verified` at the very end notify the listeners of a new_headers, one of the listeners is Informant `listener` method
- parity/informant.rs
`newHeaders` run up to call to `is_major_importing` on its target (again clinet)
- ethcore/sync/src/light_sync/mod.rs
Here `is_major_importing` tries to get state lock (read purpose only) but cannot because of previous state lock, thus deadlock
* Keep all enacted blocks notify in order
* Collect is unnecessary
* Update ChainNotify to use ChainRouteType
* Fix all ethcore fn defs
* Wrap the type within ChainRoute
* Fix private-tx and sync api
* Fix secret_store API
* Fix updater API
* Fix rpc api
* Fix informant api
* Eagerly cache enacted/retracted and remove contain_enacted/retracted
* Fix indent
* tests: should use full expr form for struct constructor
* Use into_enacted_retracted to further avoid copy
* typo: not a function
* rpc/tests: ChainRoute -> ChainRoute::new
* Improves `BestBlock` comment
* Improves `TraceDB` comment
* Improves `journaldb::Algorithm` comment.
Probably the whole enum should be renamed to `Strategy` or something alike.
* Comments some of the `Client`'s fields
* Deglobs client imports
* Fixes comments
* Extracts `import_lock` to `Importer` struct
* Extracts `verifier` to `Importer` struct
* Extracts `block_queue` to `Importer` struct
* Extracts `miner` to `Importer` struct
* Extracts `ancient_verifier` to `Importer` struct
* Extracts `rng` to `Importer` struct
* Extracts `import_old_block` to `Importer` struct
* Adds `Nonce` trait
* Adds `Balance` trait
* Adds `ChainInfo` trait
* Fixes imports for tests using `chain_info` method
* Adds `BlockInfo` trait
* Adds more `ChainInfo` imports
* Adds `BlockInfo` imports
* Adds `ReopenBlock` trait
* Adds `PrepareOpenBlock` trait
* Fixes import in tests
* Adds `CallContract` trait
* Fixes imports in tests using `call_contract` method
* Adds `TransactionInfo` trait
* Adds `RegistryInfo` trait
* Fixes imports in tests using `registry_address` method
* Adds `ScheduleInfo` trait
* Adds `ImportSealedBlock` trait
* Fixes imports in test using `import_sealed_block` method
* Adds `BroadcastProposalBlock` trait
* Migrates `Miner` to static dispatch
* Fixes tests
* Moves `calculate_enacted_retracted` to `Importer`
* Moves import-related methods to `Importer`
* Removes redundant `import_old_block` wrapper
* Extracts `import_block*` into separate trait
* Fixes tests
* Handles `Pending` in `LightFetch`
* Handles `Pending` in filters
* Handles `Pending` in `ParityClient`
* Handles `Pending` in `EthClient`
* Removes `BlockId::Pending`, partly refactors dependent code
* Adds `StateInfo` trait
* Exports `StateOrBlock` and `BlockChain` types from `client` module
* Refactors `balance` RPC using generic API
* Refactors `storage_at` RPC using generic API
* Makes `MinerService::pending_state`'s return type dynamic
* Adds `StateOrBlock` and `BlockChain` types
* Adds impl of `client::BlockChain` for `Client`
* Exports `StateInfo` trait from `client` module
* Missing `self` use
To be fixed up to "Adds impl of `client::BlockChain` for `Client`"
* Adds `number_to_id` and refactors dependent RPC methods
* Refactors `code_at` using generic API
* Adds `StateClient` trait
* Refactors RPC to use `StateClient` trait
* Reverts `client::BlockChain` trait stuff, refactors methods to accept `StateOrBlock`
* Refactors TestClient
* Adds helper function `block_number_to_id`
* Uses `block_number_to_id` instead of local function
* Handles `Pending` in `list_accounts` and `list_storage_keys`
* Attempt to use associated types for state instead of trait objects
* Simplifies `state_at_beginning`
* Extracts `call` and `call_many` into separate trait
* Refactors `build_last_hashes` to accept reference
* Exports `Call` type from the module
* Refactors `call` and `call_many` to accept state and header
* Exports `state_at` in `StateClient`
* Exports `pending_block_header` from `MinerService`
* Refactors RPC `call` method using new API
* Adds missing parentheses
* Refactors `parity::call` to use new call API
* Update .gitlab-ci.yml
fix gitlab lint
* Fixes error handling
* Refactors `traces::call` and `call_many` to use new call API
* Refactors `call_contract`
* Refactors `block_header`
* Refactors internal RPC method `block`
* Moves `estimate_gas` to `Call` trait, refactors parameters
* Refactors `estimate_gas` in RPC
* Refactors `uncle`
* Refactors RPC `transaction`
* Covers missing branches
* Makes it all compile, fixes compiler grumbles
* Adds casts in `blockchain` module
* Fixes `PendingBlock` tests, work on `MinerService`
* Adds test stubs for StateClient and EngineInfo
* Makes `state_db` public
* Adds missing impls for `TestBlockChainClient`
* Adds trait documentation
* Adds missing docs to the `state_db` module
* Fixes trivial compilation errors
* Moves `code_hash` method to a `BlockInfo` trait
* Refactors `Verifier` to be generic over client
* Refactors `TransactionFilter` to be generic over client
* Refactors `Miner` and `Client` to reflect changes in verifier and txfilter API
* Moves `ServiceTransactionChecker` back to `ethcore`
* Fixes trait bounds in `Miner` API
* Fixes `Client`
* Fixes lifetime bound in `FullFamilyParams`
* Adds comments to `FullFamilyParams`
* Fixes imports in `ethcore`
* Fixes BlockNumber handling in `code_at` and `replay_block_transactions`
* fix compile issues
* First step to redundant trait merge
* Fixes compilation error in RPC tests
* Adds mock `State` as a stub for `TestClient`
* Handles `StateOrBlock::State` in `TestBlockChainClient::balance`
* Fixes `transaction_count` RPC
* Fixes `transaction_count`
* Moves `service_transaction.json` to the `contracts` subfolder
* Fixes compilation errors in tests
* Refactors client to use `AccountData`
* Refactors client to use `BlockChain`
* Refactors miner to use aggregate traits
* Adds `SealedBlockImporter` trait
* Refactors miner to use `SealedBlockImporter` trait
* Removes unused imports
* Simplifies `RegistryInfo::registry_address`
* Fixes indentation
* Removes commented out trait bound
* do more validation of imported headers in light client
* generalize informant with traits
* informant implementation for light client
* make comment into TODO
* fix broken test
* disable full checking of headers in light client in sync tests
* owning views of blockchain data
* port blockchain and client traits to owning views
* fix ethcore tests
* use strong headers and bodies in ethcore_light
* port ethsync to use owning views
* port rpc to owning views
* port parity informant and blockchain export
