tokio: Dropping an mpsc::Receiver deadlocks

Version

tokio-0.2.2

Platform

Linux 5.0.0-36-generic #39~18.04.1-Ubuntu SMP x86_64 GNU/Linux

Description

I have a #[tokio::test] test which is failing to exit cleanly. The test spawns a bunch of tasks, does some work, then runs to completion, but when tokio tries to shut down it blocks forever. According to gdb this is happening because mpsc::Receiver::drop is calling mpsc::chan::Rx::drop which calls mpsc::chan::Tx::drop which tries to acquire a mutex and then deadlocks. Here’s the full stack trace:

#0  __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
#1  0x00007ffff77b4023 in __GI___pthread_mutex_lock (mutex=0x7ffff0002690) at ../nptl/pthread_mutex_lock.c:78
#2  0x0000555555d687e5 in std::sys::unix::mutex::Mutex::lock (self=0x7ffff0002690) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/sys/unix/mutex.rs:55
#3  0x0000555555d68671 in std::sys_common::mutex::Mutex::raw_lock (self=0x7ffff0002690) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/sys_common/mutex.rs:36
#4  0x0000555555d79b05 in std::sync::mutex::Mutex<T>::lock (self=0x7ffff0002718) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/sync/mutex.rs:220
#5  0x0000555555d7ba08 in <tokio::runtime::basic_scheduler::SchedulerPriv as tokio::task::Schedule>::schedule (self=0x7ffff00026f0, task=...)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/runtime/basic_scheduler.rs:319
#6  0x00005555558bc075 in tokio::task::harness::Harness<T,S>::wake_by_ref (self=0x7ffff6df9db0) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:315
#7  0x00005555558bdddd in tokio::task::harness::Harness<T,S>::wake_by_val (self=...) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:299
#8  0x00005555557f3ed2 in tokio::task::waker::wake_by_val (ptr=0x7ffff0013290) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/waker.rs:84
#9  0x0000555555d86222 in core::task::wake::Waker::wake (self=...) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/task/wake.rs:252
#10 0x0000555555dc9aba in tokio::sync::task::atomic_waker::AtomicWaker::wake (self=0x7ffff00141d8) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/sync/task/atomic_waker.rs:243
#11 0x000055555589b650 in <tokio::sync::mpsc::chan::Tx<T,S> as core::ops::drop::Drop>::drop (self=0x7ffff002e6f0)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/sync/mpsc/chan.rs:236
#12 0x00005555557a4bb1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#13 0x00005555557b0d91 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#14 0x000055555579f9e1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#15 0x000055555579aae1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#16 0x000055555579d34f in core::ptr::real_drop_in_place () at src/ln/peer/msg_channel.rs:227
#17 0x00005555557ad641 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#18 0x00005555557a7cb4 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#19 0x000055555578c911 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#20 0x0000555555791e40 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#21 0x0000555555799465 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#22 0x000055555579ec88 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#23 0x00005555557b2188 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#24 0x000055555589a33f in <tokio::sync::mpsc::chan::Rx<T,S> as core::ops::drop::Drop>::drop::{{closure}} (rx_fields_ptr=0x7ffff0019018)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/sync/mpsc/chan.rs:323
#25 0x0000555555729384 in tokio::loom::std::causal_cell::CausalCell<T>::with_mut (self=0x7ffff0019018, f=...)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/loom/std/causal_cell.rs:41
#26 0x000055555589896f in <tokio::sync::mpsc::chan::Rx<T,S> as core::ops::drop::Drop>::drop (self=0x7ffff0016a60)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/sync/mpsc/chan.rs:320
#27 0x00005555557aa201 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#28 0x000055555579fbee in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#29 0x00005555557aebc5 in core::ptr::real_drop_in_place () at src/ln/peer/msg_channel_manager.rs:548
#30 0x00005555557a3171 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#31 0x00005555557b4257 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#32 0x00005555557a35e1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#33 0x00005555557a3ff1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#34 0x00005555557b42b4 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#35 0x000055555579c6f1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#36 0x00005555557b498e in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#37 0x000055555579e342 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#38 0x00005555556b97ca in tokio::task::core::Core<T>::transition_to_consumed (self=0x7ffff0017420) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/core.rs:106
#39 0x00005555558f0e84 in tokio::task::harness::Harness<T,S>::do_cancel::{{closure}}::{{closure}} () at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:363
#40 0x000055555578b933 in core::ops::function::FnOnce::call_once () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ops/function.rs:223
#41 0x0000555555673cd3 in <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once (self=..., _args=()) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panic.rs:316
#42 0x0000555555778ad9 in std::panicking::try::do_call (data=0x7ffff6dfedc8 "") at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panicking.rs:287
#43 0x0000555555e2e30a in __rust_maybe_catch_panic () at src/libpanic_unwind/lib.rs:81
#44 0x00005555557765fb in std::panicking::try (f=...) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panicking.rs:265
#45 0x0000555555674933 in std::panic::catch_unwind (f=...) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panic.rs:395
#46 0x00005555558f029c in tokio::task::harness::Harness<T,S>::do_cancel::{{closure}} () at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:361
#47 0x000055555571fd48 in tokio::loom::std::causal_cell::CausalCell<T>::with_mut (self=0x7ffff0017420, f=...)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/loom/std/causal_cell.rs:41
#48 0x00005555558eda30 in tokio::task::harness::Harness<T,S>::do_cancel (self=..., res=...) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:359
#49 0x00005555558de852 in tokio::task::harness::Harness<T,S>::cancel (self=..., from_queue=true) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:342
#50 0x000055555594f5f2 in tokio::task::raw::cancel (ptr=0x7ffff00173f0, from_queue=true) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/raw.rs:196
#51 0x0000555555d491c7 in tokio::task::raw::RawTask::cancel_from_queue (self=...) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/raw.rs:145
#52 0x0000555555dba0a1 in tokio::task::Task<S>::shutdown (self=...) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/mod.rs:384
#53 0x0000555555d7ba9f in <tokio::runtime::basic_scheduler::SchedulerPriv as tokio::task::Schedule>::schedule (self=0x7ffff00026f0, task=...)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/runtime/basic_scheduler.rs:324
#54 0x00005555558bbf85 in tokio::task::harness::Harness<T,S>::wake_by_ref (self=0x7ffff6dff130) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:315
#55 0x00005555558bdcfd in tokio::task::harness::Harness<T,S>::wake_by_val (self=...) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:299
#56 0x00005555557f3f92 in tokio::task::waker::wake_by_val (ptr=0x7ffff00173f0) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/waker.rs:84
#57 0x0000555555d86222 in core::task::wake::Waker::wake (self=...) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/task/wake.rs:252
#58 0x0000555555dc9aba in tokio::sync::task::atomic_waker::AtomicWaker::wake (self=0x7ffff00168f8) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/sync/task/atomic_waker.rs:243
#59 0x000055555589aa20 in <tokio::sync::mpsc::chan::Tx<T,S> as core::ops::drop::Drop>::drop (self=0x7ffff0017510)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/sync/mpsc/chan.rs:236
#60 0x0000555555793d31 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#61 0x000055555578c451 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#62 0x00005555557b47f1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#63 0x00005555557b07c1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#64 0x00005555557c7502 in core::ptr::drop_in_place (to_drop=0x7ffff0017510) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:171
#65 alloc::sync::Arc<T>::drop_slow (self=0x7ffff00197e8) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/liballoc/sync.rs:706
#66 0x00005555557ce086 in <alloc::sync::Arc<T> as core::ops::drop::Drop>::drop (self=0x7ffff00197e8) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/liballoc/sync.rs:1234
#67 0x00005555557ab10e in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#68 0x00005555557a86f6 in core::ptr::real_drop_in_place () at src/ln/peer/manager.rs:110
#69 0x0000555555796ba1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#70 0x00005555557b1c37 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#71 0x00005555557a1751 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#72 0x00005555557a2171 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#73 0x00005555557a4fe4 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#74 0x000055555578c8f1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#75 0x000055555579a84e in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#76 0x00005555557aa402 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#77 0x00005555556b98ca in tokio::task::core::Core<T>::transition_to_consumed (self=0x7ffff00149e0) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/core.rs:106
#78 0x00005555558f0f04 in tokio::task::harness::Harness<T,S>::do_cancel::{{closure}}::{{closure}} () at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:363
#79 0x0000555555789393 in core::ops::function::FnOnce::call_once () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ops/function.rs:223
#80 0x0000555555673de3 in <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once (self=..., _args=()) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panic.rs:316
#81 0x0000555555778f19 in std::panicking::try::do_call (data=0x7ffff6dff578 "\260\366\337\366\377\177") at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panicking.rs:287
#82 0x0000555555e2e30a in __rust_maybe_catch_panic () at src/libpanic_unwind/lib.rs:81
#83 0x000055555577628b in std::panicking::try (f=...) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panicking.rs:265
#84 0x0000555555674543 in std::panic::catch_unwind (f=...) at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panic.rs:395
#85 0x00005555558f01ac in tokio::task::harness::Harness<T,S>::do_cancel::{{closure}} () at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:361
#86 0x0000555555729988 in tokio::loom::std::causal_cell::CausalCell<T>::with_mut (self=0x7ffff00149e0, f=...)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/loom/std/causal_cell.rs:41
#87 0x00005555558ee8d0 in tokio::task::harness::Harness<T,S>::do_cancel (self=..., res=...) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:359
#88 0x00005555558df4b2 in tokio::task::harness::Harness<T,S>::cancel (self=..., from_queue=false) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/harness.rs:342
#89 0x000055555594f5b2 in tokio::task::raw::cancel (ptr=0x7ffff00149b0, from_queue=false) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/raw.rs:196
#90 0x0000555555dc022b in tokio::task::list::OwnedList<T>::shutdown (self=0x7ffff00026f0) at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/task/list.rs:68
#91 0x0000555555d7be53 in <tokio::runtime::basic_scheduler::BasicScheduler<P> as core::ops::drop::Drop>::drop (self=0x7ffff6dff970)
    at /home/shum/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.2/src/runtime/basic_scheduler.rs:359
#92 0x0000555555791935 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#93 0x000055555578c977 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#94 0x0000555555796fc1 in core::ptr::real_drop_in_place () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ptr/mod.rs:181
#95 0x00005555557f651a in geelightning::ln::peer::manager::test::connect_two_peer_managers () at src/ln/peer/manager.rs:176
#96 0x00005555559429fa in geelightning::ln::peer::manager::test::connect_two_peer_managers::{{closure}} () at src/ln/peer/manager.rs:176
#97 0x0000555555788fee in core::ops::function::FnOnce::call_once () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ops/function.rs:223
#98 0x00005555559c5e2f in <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/liballoc/boxed.rs:942
#99 0x0000555555e2e30a in __rust_maybe_catch_panic () at src/libpanic_unwind/lib.rs:81
#100 0x00005555559e180a in std::panicking::try () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panicking.rs:265
#101 std::panic::catch_unwind () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panic.rs:395
#102 test::run_test_in_process () at src/libtest/lib.rs:570
#103 test::run_test::run_test_inner::{{closure}} () at src/libtest/lib.rs:473
#104 0x00005555559ba696 in std::sys_common::backtrace::__rust_begin_short_backtrace () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/sys_common/backtrace.rs:136
#105 0x00005555559beae6 in std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}} () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/thread/mod.rs:469
#106 <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panic.rs:316
#107 std::panicking::try::do_call () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panicking.rs:287
#108 0x0000555555e2e30a in __rust_maybe_catch_panic () at src/libpanic_unwind/lib.rs:81
#109 0x00005555559bf476 in std::panicking::try () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panicking.rs:265
#110 std::panic::catch_unwind () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/panic.rs:395
#111 std::thread::Builder::spawn_unchecked::{{closure}} () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/thread/mod.rs:468
#112 core::ops::function::FnOnce::call_once{{vtable-shim}} () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/ops/function.rs:223
#113 0x0000555555e192ef in <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/liballoc/boxed.rs:942
#114 0x0000555555e2d7e0 in <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once () at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/liballoc/boxed.rs:942
#115 std::sys_common::thread::start_thread () at src/libstd/sys_common/thread.rs:13
#116 std::sys::unix::thread::Thread::new::thread_start () at src/libstd/sys/unix/thread.rs:79
#117 0x00007ffff77b16db in start_thread (arg=0x7ffff6e02700) at pthread_create.c:463
#118 0x00007ffff72c288f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

My code was working fine with tokio-0.2.0-alpha.5. I’ve only hit this problem with trying to upgrade to tokio-0.2.2. Interestingly, I had previously been using futures::channel::mpsc channels but swapped them out for tokio channels in attempt to fix this bug, only to find that tokio’s channels are deadlocking in the exact same way (Receiver::drop() -> Sender::drop() -> deadlock). I also had what seems like a similar problem in my own channel-like type that I had written where a lock was being shared between a sender and a receiver, and after upgrading to tokio-0.2.2 their destructors would call each other via wake and deadlock. I was able to fix that in my own code by releasing the lock before calling wake. Based on the stack trace it looks like something similar could be happening here.