Stream deadlock

[lukesolo]

I've got a deadlock using Stream

goroutine 1 took s.recvLock.Lock() and then s.stateLock.Lock()
goroutine 2 took s.stateLock.Lock() and then s.recvLock.Lock()

#	0x4431a6	sync.runtime_SemacquireMutex+0x46							/usr/local/go/src/runtime/sema.go:71
#	0x46f32b	sync.(*Mutex).lockSlow+0xfb								/usr/local/go/src/sync/mutex.go:138
#	0xa3e8a9	sync.(*Mutex).Lock+0xd9									/usr/local/go/src/sync/mutex.go:81
#	0xa3e80c	github.com/libp2p/go-yamux.(*Stream).sendFlags+0x3c					/go/pkg/mod/github.com/libp2p/[email protected]/stream.go:194
#	0xa3e92d	github.com/libp2p/go-yamux.(*Stream).sendWindowUpdate+0x6d				/go/pkg/mod/github.com/libp2p/[email protected]/stream.go:217
#	0xa3df49	github.com/libp2p/go-yamux.(*Stream).Read+0x2c9						/go/pkg/mod/github.com/libp2p/[email protected]/stream.go:109
#	0xe0e640	github.com/libp2p/go-libp2p-swarm.(*Stream).Read+0x60					/go/pkg/mod/github.com/libp2p/[email protected]/swarm_stream.go:64
#	0xd316e7	github.com/multiformats/go-multistream.(*lazyClientConn).Read+0xa7			/go/pkg/mod/github.com/multiformats/[email protected]/lazyClient.go:75
#	0xddeb31	github.com/libp2p/go-libp2p/p2p/host/basic.(*streamWrapper).Read+0x51			/go/pkg/mod/github.com/libp2p/[email protected]/p2p/host/basic/basic_host.go:765
...

#	0x4431a6	sync.runtime_SemacquireMutex+0x46					/usr/local/go/src/runtime/sema.go:71
#	0x46f32b	sync.(*Mutex).lockSlow+0xfb						/usr/local/go/src/sync/mutex.go:138
#	0xa3e09c	sync.(*Mutex).Lock+0x41c						/usr/local/go/src/sync/mutex.go:81
#	0xa3dd54	github.com/libp2p/go-yamux.(*Stream).Read+0xd4				/go/pkg/mod/github.com/libp2p/[email protected]/stream.go:84
#	0xe0e640	github.com/libp2p/go-libp2p-swarm.(*Stream).Read+0x60			/go/pkg/mod/github.com/libp2p/[email protected]/swarm_stream.go:64
#	0xd316e7	github.com/multiformats/go-multistream.(*lazyClientConn).Read+0xa7	/go/pkg/mod/github.com/multiformats/[email protected]/lazyClient.go:75
#	0xddeb31	github.com/libp2p/go-libp2p/p2p/host/basic.(*streamWrapper).Read+0x51	/go/pkg/mod/github.com/libp2p/[email protected]/p2p/host/basic/basic_host.go:765
#	0xd1ddb1	github.com/libp2p/go-libp2p-core/helpers.AwaitEOF+0xb1			/go/pkg/mod/github.com/libp2p/[email protected]/helpers/stream.go:46
#	0xd1dcd7	github.com/libp2p/go-libp2p-core/helpers.FullClose+0x97			/go/pkg/mod/github.com/libp2p/[email protected]/helpers/stream.go:30
...

[Stebalien]

Damn. Nice catch!

[Stebalien]

Hm. Although, this raises a good question. Why do we have multiple readers here?

[lukesolo]

Thanks for fixing it!
I've found that I'm calling full close on stream concurrently with reading from it, so I think it was the cause.

[Stebalien]

Got it. In this case, just call Close. The point of FullClose is to wait to read an EOF. However, if you're already reading from the stream, there's no point.