SIGABRT - Assert fail in invariant checker

[RicoTilgner]

libtorrent version (or branch): [tags/libtorrent-1_1_7]

platform/architecture: linux x64

compiler and compiler version: gcc (GCC) 7.3.1 20180406

please describe what symptom you see, what you would expect to see instead and
how to reproduce it.

running a client with a couple (<100) share_mode only torrents, it consistently crashes after a few hours. Just built a libtorrent with invariant checks enabled and it complains about m_in_use in peer_connection::second_tick.
Full stack trace: stack.txt

[RicoTilgner]

I've been running the fix suggested in #3084 now and it's been running stable for ~15h now.

[arvidn]

good to know. that setting is 0 by default at least

[RicoTilgner]

sorry, wrong alert, libtorrent this time actually went into an infinite loop. Unfortunately I only realized after I killed it already. :/

[RicoTilgner]

ok, got it to repro again, this time with much more insight since I had a debugger running :)
It's stuck in libtorrent::torrent::second_tick, the loop over m_connections that starts at 10499. (Same place where I had the assert fail before)
idx is toggling between 31 and 32, however m_connections only has 26 elements.
I'm not exactly sure where items are deleted from m_connections, but looking at line 10527 it might be that they get removed from that container when they're disconnected.
My guess would be that the way this code tries to avoid the invalidation of the iterators doesn't work too well.

[aldenml]

@RicoTilgner can you test master? there are a lot of improvements (and fixes) there related to iteration and disconnection of m_connections

[RicoTilgner]

thanks for the tip!
Built from master now, can definitely see a difference in peer management... upload rate is way higher than with 1.1.7. :)
I'll let it run for a while now in debug mode and see if the problem still repros.

[stale]

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