[WIP] Add failing test case: atomic load on drop after panic

[phlip9]

I'm getting a "panic-while-panicking" error when something does an atomic operation during a drop after a panic. This problem surfaced after replacing a std::sync::Arc with a loom::sync::Arc in a #[should_panic] test case.

I haven't quite investigated enough to determine a proper fix, though I suspect we need to tear down the STATE only after all the threads get dropped?

In the PR is a minimal failing test case--running the test crashes the test runner, despite the added #[should_panic].

./loom$ RUST_BACKTRACE=1 cargo test atomic_load_on_drop_in_panic_crashes -- --nocapture

# ..

thread 'atomic_load_on_drop_in_panic_crashes' panicked at 'explicit panic', tests/atomic.rs:76:9
thread panicked while panicking. aborting.
error: process didn't exit successfully: `target/debug/deps/atomic-4ad683e4748fe091 atomic_load_on_drop_in_panic_crashes --nocapture` (signal: 4, SIGILL: illegal instruction)

Full log:

./loom$ RUST_BACKTRACE=1 cargo test atomic_load_on_drop_in_panic_crashes -- --nocapture
    Finished dev [unoptimized + debuginfo] target(s) in 0.02s
     Running target/debug/deps/loom-4a21a40f928e0a24

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/atomic-4ad683e4748fe091

running 1 test
thread 'atomic_load_on_drop_in_panic_crashes' panicked at 'explicit panic', tests/atomic.rs:76:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:477
   7: std::panicking::begin_panic
             at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panicking.rs:411
   8: atomic::atomic_load_on_drop_in_panic_crashes::{{closure}}
             at ./tests/atomic.rs:76
   9: loom::model::Builder::check::{{closure}}
             at ./src/model.rs:179
  10: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
             at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/liballoc/boxed.rs:787
  11: <T as loom::rt::fn_box::FnBox>::call
             at ./src/rt/fn_box.rs:10
  12: loom::rt::scheduler::spawn_threads::{{closure}}::{{closure}}
             at ./src/rt/scheduler.rs:115
  13: generator::gen_impl::GeneratorImpl<A,T>::init::{{closure}}
             at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/generator-0.6.17/src/gen_impl.rs:146
  14: core::ops::function::FnOnce::call_once{{vtable.shim}}
             at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ops/function.rs:235
  15: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
             at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/liballoc/boxed.rs:787
  16: generator::gen_impl::gen_init::{{closure}}
             at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/generator-0.6.17/src/gen_impl.rs:378
  17: core::ops::function::FnOnce::call_once
             at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ops/function.rs:235
  18: std::panicking::try::do_call
             at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panicking.rs:296
  19: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:80
  20: std::panicking::try
             at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panicking.rs:275
  21: std::panic::catch_unwind
             at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panic.rs:394
  22: generator::gen_impl::gen_init
             at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/generator-0.6.17/src/gen_impl.rs:392
thread 'atomic_load_on_drop_in_panic_crashes' panicked at 'cannot access a scoped thread local variable without calling `set` first', ~/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:186:9
stack backtrace:
   0:        0x101ee5392 - backtrace::backtrace::libunwind::trace::h50be2ccf52c4f38b
                               at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/libunwind.rs:88
   1:        0x101ee5392 - backtrace::backtrace::trace_unsynchronized::h37e5aa7f05025b64
                               at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/mod.rs:66
   2:        0x101ee5392 - std::sys_common::backtrace::_print::h1a132f5ff57517f3
                               at src/libstd/sys_common/backtrace.rs:47
   3:        0x101ee5392 - std::sys_common::backtrace::print::hd7293d834f1509d6
                               at src/libstd/sys_common/backtrace.rs:36
   4:        0x101ee5392 - std::panicking::default_hook::{{closure}}::hfd04ffdb55cf7b4e
                               at src/libstd/panicking.rs:200
   5:        0x101ee505d - std::panicking::default_hook::h0133f6f26412aeeb
                               at src/libstd/panicking.rs:214
   6:        0x101ee5b70 - std::panicking::rust_panic_with_hook::hfbf4d22eaa2b3b02
                               at src/libstd/panicking.rs:477
   7:        0x101ed626e - std::panicking::begin_panic::h8e231f1a7b71e8c9
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panicking.rs:411
   8:        0x101ebe063 - scoped_tls::ScopedKey<T>::with::hd06f6ae736fba8dc
                               at ./loom/<::std::macros::panic macros>:3
   9:        0x101ebb6c7 - loom::rt::scheduler::Scheduler::with_execution::h07bcfae0a52a1aab
                               at ./src/rt/scheduler.rs:45
  10:        0x101eb7fa5 - loom::rt::execution::h5bcf9d2b76eb8a6c
                               at ./src/rt/mod.rs:118
  11:        0x101eb7a0d - loom::rt::branch::ha11597f086676af4
                               at ./src/rt/mod.rs:51
  12:        0x101eb72d1 - loom::rt::object::Id::atomic_load::hf0b5df6c167f74f0
                               at ./src/rt/object.rs:189
  13:        0x101ece15b - loom::sync::atomic::atomic::Atomic<T>::load::h665b2160c755c0ef
                               at ./src/sync/atomic/atomic.rs:41
  14:        0x101eb8fb0 - loom::sync::atomic::int::AtomicUsize::load::h62b916452ae0124b
                               at ./src/sync/atomic/int.rs:34
  15:        0x101e4b050 - <atomic::atomic_load_on_drop_in_panic_crashes::AtomicLoadOnDrop as core::ops::drop::Drop>::drop::h8bfcf1e166a87abc
                               at ./tests/atomic.rs:57
  16:        0x101e4a735 - core::ptr::real_drop_in_place::ha70def3b9e51c275
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:175
  17:        0x101e4a028 - core::ptr::real_drop_in_place::h371c853a5044ef79
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:175
  18:        0x101e4a865 - core::ptr::real_drop_in_place::hb2fdb645bb857551
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:175
  19:        0x101e49cd8 - core::ptr::real_drop_in_place::h04186aecedfa591a
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:175
  20:        0x101e4a10c - core::ptr::real_drop_in_place::h4506a63fa5416d7f
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:175
  21:        0x101e4ac1d - core::ptr::real_drop_in_place::hf2fe1bc7a709f036
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:175
  22:        0x101e4ea06 - core::ptr::drop_in_place::h5370c5c7c8bd2638
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:165
  23:        0x101e4ea06 - <alloc::collections::vec_deque::VecDeque<T> as core::ops::drop::Drop>::drop::h4fe9896891a75224
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/liballoc/collections/vec_deque.rs:73
  24:        0x101e4a675 - core::ptr::real_drop_in_place::h9b7bc2e3d8f6d9a9
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:175
  25:        0x101e49dce - core::ptr::real_drop_in_place::h0c788ab46f666b6a
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ptr/mod.rs:175
  26:        0x101e4f465 - loom::model::Builder::check::h0ee7960ca77ba844
                               at ./loom/src/model.rs:190
  27:        0x101e4f28c - loom::model::model::h31c7061c90e513ef
                               at ./loom/src/model.rs:198
  28:        0x101e4afcd - atomic::atomic_load_on_drop_in_panic_crashes::hece1ac12fc1d0dd8
                               at ./tests/atomic.rs:61
  29:        0x101e4b8f1 - atomic::atomic_load_on_drop_in_panic_crashes::{{closure}}::h99ebdddcc02909e0
                               at ./tests/atomic.rs:46
  30:        0x101e49bd1 - core::ops::function::FnOnce::call_once::h0bc117823545eca3
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ops/function.rs:235
  31:        0x101e5e98e - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::hfd49a6c3f2e0d999
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/liballoc/boxed.rs:787
  32:        0x101ee7c2f - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:80
  33:        0x101e78297 - std::panicking::try::h68d2942b4d63deb4
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panicking.rs:275
  34:        0x101e78297 - std::panic::catch_unwind::hfea9ea3e9ce16985
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panic.rs:394
  35:        0x101e78297 - test::run_test::run_test_inner::{{closure}}::h50960bdccefe4890
                               at src/libtest/lib.rs:1408
  36:        0x101e540e5 - std::sys_common::backtrace::__rust_begin_short_backtrace::h903849e24358c5f4
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/sys_common/backtrace.rs:77
  37:        0x101e582b5 - std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}}::h41bd6ee54e13b5dc
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/thread/mod.rs:470
  38:        0x101e582b5 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::h4936f23844a9934e
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panic.rs:315
  39:        0x101e582b5 - std::panicking::try::do_call::h25b5b3d132a7a2f5
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panicking.rs:296
  40:        0x101ee7c2f - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:80
  41:        0x101e588a5 - std::panicking::try::h16fbc18df085cb11
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panicking.rs:275
  42:        0x101e588a5 - std::panic::catch_unwind::h9606131b25600a0e
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/panic.rs:394
  43:        0x101e588a5 - std::thread::Builder::spawn_unchecked::{{closure}}::h317c505e610dfd08
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libstd/thread/mod.rs:469
  44:        0x101e588a5 - core::ops::function::FnOnce::call_once{{vtable.shim}}::h6a21792d3ef0006c
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/libcore/ops/function.rs:235
  45:        0x101edb52e - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::ha8b8ab33c8814f1e
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/liballoc/boxed.rs:787
  46:        0x101ee765e - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h3eb5a968b2729d63
                               at /rustc/534b42394d743511db1335d5ed08d507ab7c6e73/src/liballoc/boxed.rs:787
  47:        0x101ee765e - std::sys_common::thread::start_thread::h49613d362bc2f444
                               at src/libstd/sys_common/thread.rs:13
  48:        0x101ee765e - std::sys::unix::thread::Thread::new::thread_start::h7ca3208863000f9f
                               at src/libstd/sys/unix/thread.rs:79
  49:     0x7fff5a1b72eb - <unknown>
  50:     0x7fff5a1ba249 - <unknown>
thread panicked while panicking. aborting.
error: process didn't exit successfully: `./loom/target/debug/deps/atomic-4ad683e4748fe091 atomic_load_on_drop_in_panic_crashes --nocapture` (signal: 4, SIGILL: illegal instruction)

[carllerche]

Ah yes, I did not think about this when implementing... I'm not sure off the top of my head what is going on. Hopefully you have more insight :)

[jonhoo]

I wonder if what happens here is related to the test harness. Specifically, that the items end up getting dropped outside of loom::model somehow?

[hawkw]

It would be really nice to have a fix for the double panic...it's definitely annoying when tests fail that way, as it's hard to get useful information out of them. Thanks for working on this!

[jonhoo]

Err, so, I'm not actually working on this, just observed what I believed to be the cause 😅 I think all that should be needed is a check for panicking somewhere in the thread_local code though.