x/playground: Faking the network example periodically deadlocks

[matthewmueller]

Problem

While reading about how "Faking the Network" works on the Go playground at https://go.dev/blog/playground, I'm running into the following error almost every time.

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [IO wait]:
internal/poll.runtime_pollWait(0x7f5332a0ee88, 0x72)
	/usr/local/go-faketime/src/runtime/netpoll.go:229 +0x89
internal/poll.(*pollDesc).wait(0xc0000c0000, 0x0, 0x0)
	/usr/local/go-faketime/src/internal/poll/fd_poll_runtime.go:84 +0x32
internal/poll.(*pollDesc).waitRead(...)
	/usr/local/go-faketime/src/internal/poll/fd_poll_runtime.go:89
internal/poll.(*FD).Accept(0xc0000c0000)
	/usr/local/go-faketime/src/internal/poll/fd_unix.go:402 +0x22c
net.(*netFD).accept(0xc0000c0000)
	/usr/local/go-faketime/src/net/fd_unix.go:173 +0x35
net.(*TCPListener).accept(0xc0000ac030)
	/usr/local/go-faketime/src/net/tcpsock_posix.go:140 +0x28
net.(*TCPListener).Accept(0xc0000ac030)
	/usr/local/go-faketime/src/net/tcpsock.go:262 +0x3d
main.main()
	/tmp/sandbox825819739/prog.go:24 +0x102

You can reproduce this by clicking on the Run button in the blog post a couple times. It does occasionally work and responds with with Hello, network. Maybe 1 in 5 times.

Screenshot

[seankhliao]

cc @toothrot

[toothrot]

Thanks, this is likely a bug in the faketime patch, as you mentioned. Our new(-ish) sandbox containers do not require the faketime patch anymore, but we've yet to remove it from Go, or update the playground for its removal, as it also impacts how program output is parsed.

I'm not positive on any ETA for resolving this.

[bcap]

Recent reddit thread on r/golang about this: https://www.reddit.com/r/golang/comments/y1z0he/headscratching_deadlock_problem/

[bcap]

Our new(-ish) sandbox containers do not require the faketime patch anymore, but we've yet to remove it from Go, or update the playground for its removal, as it also impacts how program output is parsed.

@toothrot this was roughly 1y ago. How is the situation now? Can faketime be removed from the golang playground?