diff options
Diffstat (limited to 'library/std/tests/thread_local')
| -rw-r--r-- | library/std/tests/thread_local/lib.rs | 2 | ||||
| -rw-r--r-- | library/std/tests/thread_local/tests.rs | 21 |
2 files changed, 22 insertions, 1 deletions
diff --git a/library/std/tests/thread_local/lib.rs b/library/std/tests/thread_local/lib.rs index c5291435425..26af5f1eb0a 100644 --- a/library/std/tests/thread_local/lib.rs +++ b/library/std/tests/thread_local/lib.rs @@ -1,3 +1,5 @@ +#![feature(cfg_target_thread_local)] + #[cfg(not(any(target_os = "emscripten", target_os = "wasi")))] mod tests; diff --git a/library/std/tests/thread_local/tests.rs b/library/std/tests/thread_local/tests.rs index aa020c2559c..e8278361d93 100644 --- a/library/std/tests/thread_local/tests.rs +++ b/library/std/tests/thread_local/tests.rs @@ -1,7 +1,7 @@ use std::cell::{Cell, UnsafeCell}; use std::sync::atomic::{AtomicU8, Ordering}; use std::sync::{Arc, Condvar, Mutex}; -use std::thread::{self, Builder, LocalKey}; +use std::thread::{self, LocalKey}; use std::thread_local; #[derive(Clone, Default)] @@ -345,8 +345,27 @@ fn join_orders_after_tls_destructors() { } // Test that thread::current is still available in TLS destructors. +// +// The test won't currently work without target_thread_local, aka with slow tls. +// The runtime tries very hard to drop last the TLS variable that keeps the information about the +// current thread, by using several tricks like deffering the drop to a later round of TLS destruction. +// However, this only seems to work with fast tls. +// +// With slow TLS, it seems that multiple libc implementations will just set the value to null the first +// time they encounter it, regardless of it having a destructor or not. This means that trying to +// retrieve it later in a drop impl of another TLS variable will not work. +// +// ** Apple libc: https://github.com/apple-oss-distributions/libpthread/blob/c032e0b076700a0a47db75528a282b8d3a06531a/src/pthread_tsd.c#L293 +// Sets the variable to null if it has a destructor and the value is not null. However, all variables +// created with pthread_key_create are marked as having a destructor, even if the fn ptr called with +// it is null. +// ** glibc: https://github.com/bminor/glibc/blob/e5893e6349541d871e8a25120bca014551d13ff5/nptl/nptl_deallocate_tsd.c#L59 +// ** musl: https://github.com/kraj/musl/blob/1880359b54ff7dd9f5016002bfdae4b136007dde/src/thread/pthread_key_create.c#L87 +#[cfg(target_thread_local)] #[test] fn thread_current_in_dtor() { + use std::thread::Builder; + // Go through one round of TLS destruction first. struct Defer; impl Drop for Defer { |