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x/playground: Faking the network example periodically deadlocks #48394

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matthewmueller opened this issue Sep 15, 2021 · 4 comments
Open

x/playground: Faking the network example periodically deadlocks #48394

matthewmueller opened this issue Sep 15, 2021 · 4 comments
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NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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Unreleased

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@matthewmueller
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matthewmueller commented Sep 15, 2021 •
edited

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

CleanShot 2021-09-14 at 22 40 49
@gopherbot gopherbot added this to the Unreleased milestone Sep 15, 2021
@matthewmueller matthewmueller changed the title x/playground: Faking the network example periodically deadlocking x/playground: Faking the network example periodically deadlocks Sep 15, 2021
@seankhliao seankhliao added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Sep 15, 2021
@seankhliao
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cc @toothrot

@toothrot
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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.

This was referenced Jul 3, 2022
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@ZekeLu ZekeLu mentioned this issue Jul 7, 2022
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@bcap
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bcap commented Oct 12, 2022

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

@bcap
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bcap commented Oct 12, 2022 •
edited

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?

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@toothrot @matthewmueller @bcap @gopherbot @seankhliao