Syncthing getting stuck

@AudriusButkevicius - I’m not allowed to post back to the original topic at Syncing Getting Stuck, but: I’ve got a deadlock for you!

Panic at 2017-02-02T10:01:35Z panic: deadlock detected at fmut ===fmut=== not held (writer) at model\model.go:589 goid: 313 for 5m3.4150087s (reader) ===pmut=== not held (writer)

What do you want me to do with the log files?

You can attach them here. If compressed to zip, you can just drag and drop into a post (probably, browser ymmv etc).

Ok… Nothing sensitive gets logged then? I can see it’s full of device ids, and the folder names are my customers, but… here you go: (1.8 MB)

Thanks. Good log.

It’s hung because fmut is held by NeedSize, called by the GUI. NeedSize isn’t making progress because it’s blocked on a progress emitter’s DownloadProgress method. The progress emitter isn’t making progress (hah) because it’s locked sending progress messages. Sending progress messages is taking a long time because the underlying connection is blocked in IO wait.

In other words, this is a network stall. We should have a write timeout somewhere that fires before this happens, ideally… Unfortunately I think we have a couple of abstraction layers that don’t know about timeouts, between the place where it would be set and where it would get used. :confused:

More generally, perhaps the progress emitter should be able to answer this question even when blocked sending messages. (cc @AudriusButkevicius) Also we should probably try to avoid holding those locks over network operations. But this one was deep and non-obvious…

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