netty: fix a race for channelz at server transport creation (backport v1.27.x) #6626
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A race condition was reported by user in grpc#6601: `ServerImpl.start()` calls `NettyServer.start()` while holding `ServerImpl.lock`. `NettyServer.start()` awaits a submitted runnable in eventloop. However, this pending runnable may never be executed because the eventloop might be executing some other task, like `ServerListenerImpl.transportCreated()`, that is trying to acquire `ServerImpl.lock` causing a deadlock. This PR resolves the particular issue reported in grpc#6601 for server with a single port, but `NettyServer` (https://github.com/grpc/grpc-java/blob/v1.26.0/netty/src/main/java/io/grpc/netty/NettyServer.java#L251) and `ServerImpl` (https://github.com/grpc/grpc-java/blob/v1.26.0/core/src/main/java/io/grpc/internal/ServerImpl.java#L184) in general still have the same potential risk of deadlock, which need further fix.
dapengzhang0
changed the title
ejona86
approved these changes
Jan 22, 2020
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This is a chery-pick of b8474d6
A race condition was reported by user in #6601:
ServerImpl.start()callsNettyServer.start()while holdingServerImpl.lock.NettyServer.start()awaits a submitted runnable in eventloop. However, this pending runnable may never be executed because the eventloop might be executing some other task, likeServerListenerImpl.transportCreated(), that is trying to acquireServerImpl.lockcausing a deadlock.This PR resolves the particular issue reported in #6601 for server with a single port, but
NettyServer(https://github.com/grpc/grpc-java/blob/v1.26.0/netty/src/main/java/io/grpc/netty/NettyServer.java#L251) andServerImpl(https://github.com/grpc/grpc-java/blob/v1.26.0/core/src/main/java/io/grpc/internal/ServerImpl.java#L184) in general still have the same potential risk of deadlock, which need further fix.