From 88577076069664b026736d8afb9b708fb26da54a Mon Sep 17 00:00:00 2001 From: Ferenc Szabo Date: Mon, 18 Feb 2019 07:38:14 +0100 Subject: p2p, swarm: fix node up races by granular locking (#18976) * 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 85a79b3ad3c5863f8612d25c246bcfad339f36b7, 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. (cherry picked from commit 50b872bf05b8644f14b9bea340092ced6968dd59) --- p2p/simulations/connect.go | 43 ++++++++++++++++++++++++++++++++----------- 1 file changed, 32 insertions(+), 11 deletions(-) (limited to 'p2p/simulations/connect.go') diff --git a/p2p/simulations/connect.go b/p2p/simulations/connect.go index bb7e7999a..ede96b34c 100644 --- a/p2p/simulations/connect.go +++ b/p2p/simulations/connect.go @@ -32,6 +32,9 @@ var ( // It is useful when constructing a chain network topology // when Network adds and removes nodes dynamically. func (net *Network) ConnectToLastNode(id enode.ID) (err error) { + net.lock.Lock() + defer net.lock.Unlock() + ids := net.getUpNodeIDs() l := len(ids) if l < 2 { @@ -41,29 +44,35 @@ func (net *Network) ConnectToLastNode(id enode.ID) (err error) { if last == id { last = ids[l-2] } - return net.connect(last, id) + return net.connectNotConnected(last, id) } // ConnectToRandomNode connects the node with provided NodeID // to a random node that is up. func (net *Network) ConnectToRandomNode(id enode.ID) (err error) { - selected := net.GetRandomUpNode(id) + net.lock.Lock() + defer net.lock.Unlock() + + selected := net.getRandomUpNode(id) if selected == nil { return ErrNodeNotFound } - return net.connect(selected.ID(), id) + return net.connectNotConnected(selected.ID(), id) } // ConnectNodesFull connects all nodes one to another. // It provides a complete connectivity in the network // which should be rarely needed. func (net *Network) ConnectNodesFull(ids []enode.ID) (err error) { + net.lock.Lock() + defer net.lock.Unlock() + if ids == nil { ids = net.getUpNodeIDs() } for i, lid := range ids { for _, rid := range ids[i+1:] { - if err = net.connect(lid, rid); err != nil { + if err = net.connectNotConnected(lid, rid); err != nil { return err } } @@ -74,12 +83,19 @@ func (net *Network) ConnectNodesFull(ids []enode.ID) (err error) { // ConnectNodesChain connects all nodes in a chain topology. // If ids argument is nil, all nodes that are up will be connected. func (net *Network) ConnectNodesChain(ids []enode.ID) (err error) { + net.lock.Lock() + defer net.lock.Unlock() + + return net.connectNodesChain(ids) +} + +func (net *Network) connectNodesChain(ids []enode.ID) (err error) { if ids == nil { ids = net.getUpNodeIDs() } l := len(ids) for i := 0; i < l-1; i++ { - if err := net.connect(ids[i], ids[i+1]); err != nil { + if err := net.connectNotConnected(ids[i], ids[i+1]); err != nil { return err } } @@ -89,6 +105,9 @@ func (net *Network) ConnectNodesChain(ids []enode.ID) (err error) { // ConnectNodesRing connects all nodes in a ring topology. // If ids argument is nil, all nodes that are up will be connected. func (net *Network) ConnectNodesRing(ids []enode.ID) (err error) { + net.lock.Lock() + defer net.lock.Unlock() + if ids == nil { ids = net.getUpNodeIDs() } @@ -96,15 +115,18 @@ func (net *Network) ConnectNodesRing(ids []enode.ID) (err error) { if l < 2 { return nil } - if err := net.ConnectNodesChain(ids); err != nil { + if err := net.connectNodesChain(ids); err != nil { return err } - return net.connect(ids[l-1], ids[0]) + return net.connectNotConnected(ids[l-1], ids[0]) } // ConnectNodesStar connects all nodes into a star topology // If ids argument is nil, all nodes that are up will be connected. func (net *Network) ConnectNodesStar(ids []enode.ID, center enode.ID) (err error) { + net.lock.Lock() + defer net.lock.Unlock() + if ids == nil { ids = net.getUpNodeIDs() } @@ -112,16 +134,15 @@ func (net *Network) ConnectNodesStar(ids []enode.ID, center enode.ID) (err error if center == id { continue } - if err := net.connect(center, id); err != nil { + if err := net.connectNotConnected(center, id); err != nil { return err } } return nil } -// connect connects two nodes but ignores already connected error. -func (net *Network) connect(oneID, otherID enode.ID) error { - return ignoreAlreadyConnectedErr(net.Connect(oneID, otherID)) +func (net *Network) connectNotConnected(oneID, otherID enode.ID) error { + return ignoreAlreadyConnectedErr(net.connect(oneID, otherID)) } func ignoreAlreadyConnectedErr(err error) error { -- cgit v1.2.3