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std: store key-based TLS variables in a hashmap #156743

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std: store key-based TLS variables in a hashmap #156743

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30 changes: 0 additions & 30 deletions library/std/src/sys/thread_local/guard/key.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@
use crate::ptr;
use crate::sys::thread_local::key::{LazyKey, set};

#[cfg(target_thread_local)]
pub fn enable() {
use crate::sys::thread_local::destructors;

Expand All @@ -29,32 +28,3 @@ pub fn enable() {
}
}
}

/// On platforms with key-based TLS, the system runs the destructors for us.
/// We still have to make sure that [`crate::rt::thread_cleanup`] is called,
/// however. This is done by deferring the execution of a TLS destructor to
/// the next round of destruction inside the TLS destructors.
#[cfg(not(target_thread_local))]
pub fn enable() {
const DEFER: *mut u8 = ptr::without_provenance_mut(1);
const RUN: *mut u8 = ptr::without_provenance_mut(2);

static CLEANUP: LazyKey = LazyKey::new(Some(run));

unsafe { set(CLEANUP.force(), DEFER) }

unsafe extern "C" fn run(state: *mut u8) {
if state == DEFER {
// Make sure that this function is run again in the next round of
// TLS destruction. If there is no further round, there will be leaks,
// but that's okay, `thread_cleanup` is not guaranteed to be called.
unsafe { set(CLEANUP.force(), RUN) }
} else {
debug_assert_eq!(state, RUN);
// If the state is still RUN in the next round of TLS destruction,
// it means that no other TLS destructors defined by this runtime
// have been run, as they would have set the state to DEFER.
crate::rt::thread_cleanup();
}
}
}
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