get_handle_mut::<PgConnectionHandle> hands out a &'static mut from a blocking-pool thread while the main thread can take_handle it #10338

Problem

get_handle_mut::<PgConnectionHandle> hands out a &'static mut reference from a tokio blocking-pool thread, while the main thread can simultaneously call take_handle on the very same handle — js_pg_client_end does exactly that.

Why it matters

This is an aliasing hazard: two threads can hold a live mutable reference (one via get_handle_mut, one via take_handle on the main thread) to the same underlying connection handle at the same time, which is undefined behavior in Rust regardless of whether a concrete crash has been observed. This is a pre-existing issue in the legacy spawn_blocking-based path, independent of the turnloop migration.

What would fix it

Whatever synchronization already protects other handle-table accesses (a lock, or restructuring so a handle in active use on a blocking-pool thread cannot be concurrently taken from the main thread) needs to cover PgConnectionHandle too. At minimum, take_handle should not be able to race a live get_handle_mut borrow on the same handle.