Auto merge of #127912 - joboet:tls_dtor_thread_current, r=cuviper

std: make `thread::current` available in all `thread_local!` destructors

... and thereby allow the panic runtime to always print the right thread name.

This works by modifying the TLS destructor system to schedule a runtime cleanup function after all other TLS destructors registered by `std` have run. Unfortunately, this doesn't affect foreign TLS destructors, `thread::current` will still panic there.

Additionally, the thread ID returned by `current_id` will now always be available, even inside the global allocator, and will not change during the lifetime of one thread (this was previously the case with key-based TLS).

The mechanisms I added for this (`local_pointer` and `thread_cleanup`) will also allow finally fixing #111272 by moving the signal stack to a similar runtime-cleanup TLS variable.

1 files changed, 4 insertions, 2 deletions

diff --git a/library/std/src/sys/sync/rwlock/queue.rs b/library/std/src/sys/sync/rwlock/queue.rs
index 0e658328c2e..733f51cae8c 100644
--- a/library/std/src/sys/sync/rwlock/queue.rs
+++ b/library/std/src/sys/sync/rwlock/queue.rs
@@ -113,7 +113,7 @@ use crate::mem;
 use crate::ptr::{self, NonNull, null_mut, without_provenance_mut};
 use crate::sync::atomic::Ordering::{AcqRel, Acquire, Relaxed, Release};
 use crate::sync::atomic::{AtomicBool, AtomicPtr};
-use crate::thread::{self, Thread};
+use crate::thread::{self, Thread, ThreadId};
 
 // Locking uses exponential backoff. `SPIN_COUNT` indicates how many times the
 // locking operation will be retried.
@@ -200,7 +200,9 @@ impl Node {
     fn prepare(&mut self) {
         // Fall back to creating an unnamed `Thread` handle to allow locking in
         // TLS destructors.
-        self.thread.get_or_init(|| thread::try_current().unwrap_or_else(Thread::new_unnamed));
+        self.thread.get_or_init(|| {
+            thread::try_current().unwrap_or_else(|| Thread::new_unnamed(ThreadId::new()))
+        });
         self.completed = AtomicBool::new(false);
     }