HubSwitchGuard should not be Send

[Ten0]

How do you use Sentry?

Sentry SaaS (sentry.io)

SDK version

0.46.0

Steps to reproduce

1. let sg = HubSwitchGuard::new(Hub::current())
2. std::thread::spawn(move|| { let _ = sg; }

Expected result

Compilation error

Actual result

New thread gets its hub replaced by that of the parent thread, and parent thread never recovers their own hub.

Because HubSwitchGuard is about managing the thread-local that represents the current hub for this thread, it really doesn't make sense to move it to another thread, and as such that should be prevented. (HubSwitchGuard should be !Send)

This can be achieved with e.g. a field like this _make_type_not_send: std::marker::PhantomData<std::sync::MutexGuard<'static, ()>>,

[linear]

RUST-130

[Ten0]

Hmm probably making it !Sync would cause issues because it couldn't be used here:

sentry-rust/sentry-tracing/src/layer.rs

Line 374 in 196501d

data.hub_switch_guard.take();

[szokeasaurusrex]

Hi, thanks for reporting, I will investigate further and get back to you

[szokeasaurusrex]

Hey, thanks for your patience. This looks like a legitimate problem. I am working on a fix, which should hopefully also fix #946