"panicked while panicking" issues when drop handlers run concurrent code

Shuttle does not properly handle concurrent code run in drop handlers after a panic. It can run into a panic while panicking, which kills the process. Here's a minimal example. It needs to hit a particular schedule which happens with probability 1/2.

```rust
use shuttle::sync::{Arc, Mutex};

struct Foo(Arc>);

impl Drop for Foo {
fn drop(&mut self) {
let _m = self.0.lock().unwrap();
}
}

#[test]
fn double_panic() {
shuttle::check_random(
|| {
let mutex = Arc::new(Mutex::new(()));
let _f = Foo(mutex.clone());

shuttle::thread::spawn(move || {
// The double panic happens in executions where this thread
// switches to the main thread inside the `lock` function.
let _m = mutex.lock().unwrap();
});

panic!("panic in test code");
},
100,
);
}
```

Error output

```
test panicked in task 'main-thread'
failing schedule:
"
910103a4d0e880c2fbe3a89f0108
"
pass that string to `shuttle::replay` to replay the failure
thread 'double_panic' panicked at 'panic in test code', src/lib.rs:24:13
stack backtrace:
0: rust_begin_unwind
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:578:5
1: core::panicking::panic_fmt
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panicking.rs:67:14
2: proptest_shuttle_test::double_panic::{{closure}}
at ./src/lib.rs:24:13
3: shuttle::runtime::runner::Runner::run::{{closure}}::{{closure}}::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/runner.rs:69:100
4: shuttle::thread::thread_fn
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/thread.rs:102:15
5: shuttle::runtime::execution::Execution::run::{{closure}}::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:67:25
6: core::ops::function::FnOnce::call_once{{vtable.shim}}
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
7: as core::ops::function::FnOnce>::call_once
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1973:9
8: shuttle::runtime::thread::continuation::Continuation::new::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/thread/continuation.rs:87:21
9: generator::gen_impl::GeneratorImpl::init_code::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:336:21
10: generator::stack::StackBox::call_once
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/stack/mod.rs:139:13
11: generator::stack::Func::call_once
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/stack/mod.rs:121:9
12: generator::gen_impl::gen_init::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:552:9
13: core::ops::function::FnOnce::call_once
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
14: std::panicking::try::do_call
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:485:40
15: ___rust_try
16: std::panicking::try
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:449:19
17: std::panic::catch_unwind
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panic.rs:140:14
18: generator::gen_impl::catch_unwind_filter
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:543:5
19: generator::gen_impl::gen_init
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:570:25
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
thread 'double_panic' panicked at 'test panicked in task 'main-thread'
failing schedule:
"
910103a4d0e880c2fbe3a89f0108
"
pass that string to `shuttle::replay` to replay the failure', /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:144:17
stack backtrace:
0: 0x10f665546 - std::backtrace_rs::backtrace::libunwind::trace::h0a908cd09b5a35f9
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
1: 0x10f665546 - std::backtrace_rs::backtrace::trace_unsynchronized::hc0e7d5d16c14a788
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: 0x10f665546 - std::sys_common::backtrace::_print_fmt::hcf9ca6805c7eb2fe
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:65:5
3: 0x10f665546 - ::fmt::hae51cb91d407e2ef
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:44:22
4: 0x10f68103b - core::fmt::write::h746bc0969202388b
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/fmt/mod.rs:1254:17
5: 0x10f66250c - std::io::Write::write_fmt::h4098c2c7437a0bd7
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/io/mod.rs:1698:15
6: 0x10f66531a - std::sys_common::backtrace::_print::he6d3aef1f6c73e2d
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:47:5
7: 0x10f66531a - std::sys_common::backtrace::print::h8360bf0158e89b36
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:34:9
8: 0x10f666f70 - std::panicking::default_hook::{{closure}}::hedf04c568eb6e0bc
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:269:22
9: 0x10f666d20 - std::panicking::default_hook::h62889b2c29e2347d
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:288:9
10: 0x10f6255c4 - as core::ops::function::Fn>::call::he6b83307c909e624
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1987:9
11: 0x10f5fe425 - shuttle::runtime::failure::init_panic_hook::{{closure}}::{{closure}}::h42de85c8fa97934f
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/failure.rs:151:13
12: 0x10f6255c4 - as core::ops::function::Fn>::call::he6b83307c909e624
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1987:9
13: 0x10f6269e5 - generator::gen_impl::catch_unwind_filter::{{closure}}::{{closure}}::h24c0991694e38682
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:539:13
14: 0x10f66764a - as core::ops::function::Fn>::call::h5ccd129639ee877c
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1987:9
15: 0x10f66764a - std::panicking::rust_panic_with_hook::h22edd02828aff274
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:695:13
16: 0x10f6673e4 - std::panicking::begin_panic_handler::{{closure}}::h6895f44a9b7e2caa
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:582:13
17: 0x10f665989 - std::sys_common::backtrace::__rust_end_short_backtrace::h013519e9b77978c5
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:150:18
18: 0x10f66712d - rust_begin_unwind
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:578:5
19: 0x10f68d053 - core::panicking::panic_fmt::h2a51b60c12d11322
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panicking.rs:67:14
20: 0x10f5a7221 - core::panicking::panic_display::hbd949b297acfd5f4
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panicking.rs:150:5
21: 0x10f5a6ae1 - shuttle::runtime::execution::Execution::step::h00314f3fd4ea0f15
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:144:17
22: 0x10f59d89f - shuttle::runtime::execution::Execution::run::{{closure}}::h435d08498b5500db
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:74:19
23: 0x10f5a92b9 - scoped_tls::ScopedKey::set::hf9c179dc9c5d2b9e
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/scoped-tls-1.0.1/src/lib.rs:137:9
24: 0x10f59d6d1 - shuttle::runtime::execution::Execution::run::hb1f06acf42b88a14
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:64:9
25: 0x10f593d2a - shuttle::runtime::runner::Runner::run::{{closure}}::{{closure}}::h62c8cb787820efb7
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/runner.rs:69:64
26: 0x10f592555 - tracing::span::Span::in_scope::h9482e775058da9fb
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tracing-0.1.37/src/span.rs:1102:9
27: 0x10f593bbe - shuttle::runtime::runner::Runner::run::{{closure}}::h5b30f2386550abea
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/runner.rs:69:17
28: 0x10f5a9197 - scoped_tls::ScopedKey::set::h46c950750c8aadb1
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/scoped-tls-1.0.1/src/lib.rs:137:9
29: 0x10f5932c3 - shuttle::runtime::runner::Runner::run::h6ed27f200638e525
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/runner.rs:49:9
30: 0x10f5a1159 - shuttle::check_random::hf2b9458e9d07ee53
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/lib.rs:313:5
31: 0x10f59223e - proptest_shuttle_test::double_panic::h236e26cd0e9ef228
at /Users/kraglb/Code/proptest-shuttle-test/src/lib.rs:13:5
32: 0x10f5a6fb9 - proptest_shuttle_test::double_panic::{{closure}}::h803d69b63cde3b8b
at /Users/kraglb/Code/proptest-shuttle-test/src/lib.rs:12:19
33: 0x10f594658 - core::ops::function::FnOnce::call_once::hc924793af4a1d820
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
34: 0x10f5e34c2 - core::ops::function::FnOnce::call_once::h0fe66ffa3f9dbea8
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
35: 0x10f5e34c2 - test::__rust_begin_short_backtrace::h460edc73ee3d7292
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/test/src/lib.rs:655:18
36: 0x10f5b0281 - test::run_test::{{closure}}::hcb97f2f14ca1b43f
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/test/src/lib.rs:646:30
37: 0x10f5b0281 - core::ops::function::FnOnce::call_once{{vtable.shim}}::hdfe6b8e984779cce
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
38: 0x10f5e22c1 - as core::ops::function::FnOnce>::call_once::hfa918f0892d6e1a1
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1973:9
39: 0x10f5e22c1 - as core::ops::function::FnOnce<()>>::call_once::h71c8bbcc51698713
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panic/unwind_safe.rs:271:9
40: 0x10f5e22c1 - std::panicking::try::do_call::h890697a79ad71324
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:485:40
41: 0x10f5e22c1 - std::panicking::try::ha3f7932050f4d091
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:449:19
42: 0x10f5e22c1 - std::panic::catch_unwind::hc2bb78c2421caad4
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panic.rs:140:14
43: 0x10f5e22c1 - test::run_test_in_process::hfaa808ccf4afcea3
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/test/src/lib.rs:678:27
44: 0x10f5e22c1 - test::run_test::run_test_inner::{{closure}}::h6df30ee50946e418
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/test/src/lib.rs:572:39
45: 0x10f5aaba7 - test::run_test::run_test_inner::{{closure}}::h28731cdeaae649ee
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/test/src/lib.rs:599:37
46: 0x10f5aaba7 - std::sys_common::backtrace::__rust_begin_short_backtrace::he77a8a07f5d086a1
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:134:18
47: 0x10f5b0151 - std::thread::Builder::spawn_unchecked_::{{closure}}::{{closure}}::h7325a38e91958334
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/thread/mod.rs:526:17
48: 0x10f5b0151 - as core::ops::function::FnOnce<()>>::call_once::h4f76313c8805442a
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panic/unwind_safe.rs:271:9
49: 0x10f5b0151 - std::panicking::try::do_call::h8ffd919c7cd22e24
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:485:40
50: 0x10f5b0151 - std::panicking::try::he40bc179d7d75f43
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:449:19
51: 0x10f5b0151 - std::panic::catch_unwind::hb878b7a33e4fb646
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panic.rs:140:14
52: 0x10f5b0151 - std::thread::Builder::spawn_unchecked_::{{closure}}::hf2774d6144cce2f7
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/thread/mod.rs:525:30
53: 0x10f5b0151 - core::ops::function::FnOnce::call_once{{vtable.shim}}::hc09679af1629946e
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
54: 0x10f66b8a9 - as core::ops::function::FnOnce>::call_once::h3813d4e7f4f8581d
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1973:9
55: 0x10f66b8a9 - as core::ops::function::FnOnce>::call_once::ha3873a2c5aad6d58
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1973:9
56: 0x10f66b8a9 - std::sys::unix::thread::Thread::new::thread_start::ha9b8d2206382b425
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys/unix/thread.rs:108:17
57: 0x7ff8045c94e1 - __pthread_start
thread panicked while panicking. aborting.
error: test failed, to rerun pass `-p proptest-shuttle-test --lib`

Caused by:
process didn't exit successfully: `/Users/kraglb/Code/proptest-shuttle-test/target/debug/deps/proptest_shuttle_test-cf7e6e3a9da694c9 double_panic --exact --nocapture` (signal: 6, SIGABRT: process abort signal)
```

Replaying the above schedule (`910103a4d0e880c2fbe3a89f0108`) also leads to a panic while panicking, because the schedule stops at the first panic, and so we hit `'schedule ended early'` when we want to make further scheduling decisions after the first panic.

Replay error output

```
test panicked in task 'main-thread'
failing schedule:
"
910103a4d0e880c2fbe3a89f0108
"
pass that string to `shuttle::replay` to replay the failure
thread 'replay_double_panic' panicked at 'panic in test code', src/lib.rs:43:13
stack backtrace:
0: rust_begin_unwind
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:578:5
1: core::panicking::panic_fmt
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panicking.rs:67:14
2: proptest_shuttle_test::replay_double_panic::{{closure}}
at ./src/lib.rs:43:13
3: shuttle::runtime::runner::Runner::run::{{closure}}::{{closure}}::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/runner.rs:69:100
4: shuttle::thread::thread_fn
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/thread.rs:102:15
5: shuttle::runtime::execution::Execution::run::{{closure}}::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:67:25
6: core::ops::function::FnOnce::call_once{{vtable.shim}}
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
7: as core::ops::function::FnOnce>::call_once
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1973:9
8: shuttle::runtime::thread::continuation::Continuation::new::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/thread/continuation.rs:87:21
9: generator::gen_impl::GeneratorImpl::init_code::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:336:21
10: generator::stack::StackBox::call_once
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/stack/mod.rs:139:13
11: generator::stack::Func::call_once
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/stack/mod.rs:121:9
12: generator::gen_impl::gen_init::{{closure}}
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:552:9
13: core::ops::function::FnOnce::call_once
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
14: std::panicking::try::do_call
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:485:40
15: ___rust_try
16: std::panicking::try
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:449:19
17: std::panic::catch_unwind
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panic.rs:140:14
18: generator::gen_impl::catch_unwind_filter
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:543:5
19: generator::gen_impl::gen_init
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:570:25
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
thread 'replay_double_panic' panicked at 'schedule ended early', /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/scheduler/replay.rs:69:13
stack backtrace:
0: 0x10f3e3036 - std::backtrace_rs::backtrace::libunwind::trace::h0a908cd09b5a35f9
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
1: 0x10f3e3036 - std::backtrace_rs::backtrace::trace_unsynchronized::hc0e7d5d16c14a788
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: 0x10f3e3036 - std::sys_common::backtrace::_print_fmt::hcf9ca6805c7eb2fe
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:65:5
3: 0x10f3e3036 - ::fmt::hae51cb91d407e2ef
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:44:22
4: 0x10f3feb2b - core::fmt::write::h746bc0969202388b
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/fmt/mod.rs:1254:17
5: 0x10f3dfffc - std::io::Write::write_fmt::h4098c2c7437a0bd7
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/io/mod.rs:1698:15
6: 0x10f3e2e0a - std::sys_common::backtrace::_print::he6d3aef1f6c73e2d
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:47:5
7: 0x10f3e2e0a - std::sys_common::backtrace::print::h8360bf0158e89b36
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:34:9
8: 0x10f3e4a60 - std::panicking::default_hook::{{closure}}::hedf04c568eb6e0bc
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:269:22
9: 0x10f3e4810 - std::panicking::default_hook::h62889b2c29e2347d
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:288:9
10: 0x10f3a2cf4 - as core::ops::function::Fn>::call::he6b83307c909e624
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1987:9
11: 0x10f377ed5 - shuttle::runtime::failure::init_panic_hook::{{closure}}::{{closure}}::h42de85c8fa97934f
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/failure.rs:151:13
12: 0x10f3a2cf4 - as core::ops::function::Fn>::call::he6b83307c909e624
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1987:9
13: 0x10f3a4115 - generator::gen_impl::catch_unwind_filter::{{closure}}::{{closure}}::h24c0991694e38682
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:539:13
14: 0x10f3e513a - as core::ops::function::Fn>::call::h5ccd129639ee877c
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1987:9
15: 0x10f3e513a - std::panicking::rust_panic_with_hook::h22edd02828aff274
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:695:13
16: 0x10f3e4e93 - std::panicking::begin_panic_handler::{{closure}}::h6895f44a9b7e2caa
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:580:13
17: 0x10f3e3479 - std::sys_common::backtrace::__rust_end_short_backtrace::h013519e9b77978c5
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/sys_common/backtrace.rs:150:18
18: 0x10f3e4c1d - rust_begin_unwind
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:578:5
19: 0x10f40ab43 - core::panicking::panic_fmt::h2a51b60c12d11322
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panicking.rs:67:14
20: 0x10f376656 - ::next_task::h8ea057550dca6f79
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/scheduler/replay.rs:69:13
21: 0x10f304bd6 - as shuttle::scheduler::Scheduler>::next_task::hf2b74c3aa7bbc9ff
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/scheduler/metrics.rs:92:22
22: 0x10f371630 - shuttle::runtime::execution::ExecutionState::schedule::h89fc2a09bfd49009
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:567:26
23: 0x10f3708cd - shuttle::runtime::execution::ExecutionState::maybe_yield::{{closure}}::h98f52af81cfe20db
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:383:26
24: 0x10f36fd8a - shuttle::runtime::execution::ExecutionState::try_with::{{closure}}::hb9dcd22ea989e68b
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:258:26
25: 0x10f37e402 - scoped_tls::ScopedKey::with::hdc6b8fddccec0df1
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/scoped-tls-1.0.1/src/lib.rs:171:13
26: 0x10f36f366 - shuttle::runtime::execution::ExecutionState::try_with::h4bb2a7396c03ac15
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:256:13
27: 0x10f36f06d - shuttle::runtime::execution::ExecutionState::with::ha3108570b68fa7dc
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:245:9
28: 0x10f370899 - shuttle::runtime::execution::ExecutionState::maybe_yield::hdca648f3f72a96f5
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:377:9
29: 0x10f363f9d - shuttle::runtime::thread::continuation::switch::h1ec241841f45c810
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/thread/continuation.rs:259:8
30: 0x10f31d5ba - shuttle::sync::mutex::Mutex::lock::hc5a83ab06bf8d63a
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/sync/mutex.rs:71:13
31: 0x10f303a9d - ::drop::hb411a29ef0c6f032
at /Users/kraglb/Code/proptest-shuttle-test/src/lib.rs:7:18
32: 0x10f300f75 - core::ptr::drop_in_place::h04cb8183f3606aa5
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ptr/mod.rs:490:1
33: 0x10f31c3ba - proptest_shuttle_test::replay_double_panic::{{closure}}::h91ac582f84cd9cfb
at /Users/kraglb/Code/proptest-shuttle-test/src/lib.rs:44:9
34: 0x10f2ffa7d - shuttle::runtime::runner::Runner::run::{{closure}}::{{closure}}::{{closure}}::h9e7bb64bc90b3ad9
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/runner.rs:69:100
35: 0x10f3129d3 - shuttle::thread::thread_fn::hcbc2b34780f1e487
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/thread.rs:102:15
36: 0x10f30df1a - shuttle::runtime::execution::Execution::run::{{closure}}::{{closure}}::h857f7da1b457d850
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/execution.rs:67:25
37: 0x10f3002d4 - core::ops::function::FnOnce::call_once{{vtable.shim}}::h1667835ca21b1394
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
38: 0x10f36ea1e - as core::ops::function::FnOnce>::call_once::hc62867ebb53a9c78
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/alloc/src/boxed.rs:1973:9
39: 0x10f363431 - shuttle::runtime::thread::continuation::Continuation::new::{{closure}}::hd949b502d8cd8af8
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/shuttle-0.6.1/src/runtime/thread/continuation.rs:87:21
40: 0x10f397039 - generator::gen_impl::GeneratorImpl::init_code::{{closure}}::h71323f9c2b036413
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:336:21
41: 0x10f38b33f - generator::stack::StackBox::call_once::h856ea0bb4902f7b8
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/stack/mod.rs:139:13
42: 0x10f3a2daf - generator::stack::Func::call_once::h7b0f46ad5849766c
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/stack/mod.rs:121:9
43: 0x10f3a42c3 - generator::gen_impl::gen_init::{{closure}}::hb5197d56bc3a43dd
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:552:9
44: 0x10f3a1115 - core::ops::function::FnOnce::call_once::h44414163bef47564
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5
45: 0x10f3a29a8 - std::panicking::try::do_call::hf38821f2c0f1e724
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:485:40
46: 0x10f3a2d1d - ___rust_try
47: 0x10f3a2917 - std::panicking::try::h6b11b2e34ab64c77
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:449:19
48: 0x10f3a20b1 - std::panic::catch_unwind::ha56f94586618f63b
at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panic.rs:140:14
49: 0x10f3a3fe0 - generator::gen_impl::catch_unwind_filter::h345f378589a64220
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:543:5
50: 0x10f3a414e - generator::gen_impl::gen_init::h25dfd0df328bbc96
at /Users/kraglb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/generator-0.7.4/src/gen_impl.rs:570:25
thread panicked while panicking. aborting.
error: test failed, to rerun pass `-p proptest-shuttle-test --lib`

Caused by:
process didn't exit successfully: `/Users/kraglb/Code/proptest-shuttle-test/target/debug/deps/proptest_shuttle_test-cf7e6e3a9da694c9 replay_double_panic --exact --nocapture` (signal: 6, SIGABRT: process abort signal)
```

Start by reproducing the minimal double_panic example with the failing replay schedule. Then inspect runtime/execution.rs, runtime/runner.rs, thread.rs, and runtime/failure.rs, which appear in the report. Done means drop-handler concurrency during a panic no longer causes a second panic that kills the process, with the regression covered by a test.

Written by the indexing model from the issue text.