1. 18 Feb, 2019 1 commit
    • Ferenc Szabo's avatar
      p2p, swarm: fix node up races by granular locking (#18976) · 50b872bf
      Ferenc Szabo authored
      * swarm/network: DRY out repeated giga comment
      
      I not necessarily agree with the way we wait for event propagation.
      But I truly disagree with having duplicated giga comments.
      
      * p2p/simulations: encapsulate Node.Up field so we avoid data races
      
      The Node.Up field was accessed concurrently without "proper" locking.
      There was a lock on Network and that was used sometimes to access
      the  field. Other times the locking was missed and we had
      a data race.
      
      For example: https://github.com/ethereum/go-ethereum/pull/18464
      The case above was solved, but there were still intermittent/hard to
      reproduce races. So let's solve the issue permanently.
      
      resolves: ethersphere/go-ethereum#1146
      
      * p2p/simulations: fix unmarshal of simulations.Node
      
      Making Node.Up field private in 13292ee897e345045fbfab3bda23a77589a271c1
      broke TestHTTPNetwork and TestHTTPSnapshot. Because the default
      UnmarshalJSON does not handle unexported fields.
      
      Important: The fix is partial and not proper to my taste. But I cut
      scope as I think the fix may require a change to the current
      serialization format. New ticket:
      https://github.com/ethersphere/go-ethereum/issues/1177
      
      * p2p/simulations: Add a sanity test case for Node.Config UnmarshalJSON
      
      * p2p/simulations: revert back to defer Unlock() pattern for Network
      
      It's a good patten to call `defer Unlock()` right after `Lock()` so
      (new) error cases won't miss to unlock. Let's get back to that pattern.
      
      The patten was abandoned in 85a79b3a,
      while fixing a data race. That data race does not exist anymore,
      since the Node.Up field got hidden behind its own lock.
      
      * p2p/simulations: consistent naming for test providers Node.UnmarshalJSON
      
      * p2p/simulations: remove JSON annotation from private fields of Node
      
      As unexported fields are not serialized.
      
      * p2p/simulations: fix deadlock in Network.GetRandomDownNode()
      
      Problem: GetRandomDownNode() locks -> getDownNodeIDs() ->
      GetNodes() tries to lock -> deadlock
      
      On Network type, unexported functions must assume that `net.lock`
      is already acquired and should not call exported functions which
      might try to lock again.
      
      * p2p/simulations: ensure method conformity for Network
      
      Connect* methods were moved to p2p/simulations.Network from
      swarm/network/simulation. However these new methods did not follow
      the pattern of Network methods, i.e., all exported method locks
      the whole Network either for read or write.
      
      * p2p/simulations: fix deadlock during network shutdown
      
      `TestDiscoveryPersistenceSimulationSimAdapter` often got into deadlock.
      The execution was stuck on two locks, i.e, `Kademlia.lock` and
      `p2p/simulations.Network.lock`. Usually the test got stuck once in each
      20 executions with high confidence.
      
      `Kademlia` was stuck in `Kademlia.EachAddr()` and `Network` in
      `Network.Stop()`.
      
      Solution: in `Network.Stop()` `net.lock` must be released before
      calling `node.Stop()` as stopping a node (somehow - I did not find
      the exact code path) causes `Network.InitConn()` to be called from
      `Kademlia.SuggestPeer()` and that blocks on `net.lock`.
      
      Related ticket: https://github.com/ethersphere/go-ethereum/issues/1223
      
      * swarm/state: simplify if statement in DBStore.Put()
      
      * p2p/simulations: remove faulty godoc from private function
      
      The comment started with the wrong method name.
      
      The method is simple and self explanatory. Also, it's private.
      => Let's just remove the comment.
      50b872bf
  2. 17 Feb, 2019 1 commit
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