Rollup merge of rust-lang#123807 - joboet:sys_common_thread, r=jhpratt

Remove `sys_common::thread`

Part of rust-lang#117276.

The stack size calculation isn't system-specific at all and can just live together with the rest of the spawn logic.

library/std/src/sys_common/mod.rs

@@ -25,7 +25,6 @@ pub mod fs;
 pub mod io;
 pub mod lazy_box;
 pub mod process;
-pub mod thread;
 pub mod thread_local_dtor;
 pub mod thread_parking;
 pub mod wstr;

library/std/src/thread/mod.rs

@@ -160,6 +160,7 @@ mod tests;
 
 use crate::any::Any;
 use crate::cell::{OnceCell, UnsafeCell};
+use crate::env;
 use crate::ffi::{CStr, CString};
 use crate::fmt;
 use crate::io;
@@ -171,9 +172,9 @@ use crate::panicking;
 use crate::pin::Pin;
 use crate::ptr::addr_of_mut;
 use crate::str;
+use crate::sync::atomic::{AtomicUsize, Ordering};
 use crate::sync::Arc;
 use crate::sys::thread as imp;
-use crate::sys_common::thread;
 use crate::sys_common::thread_parking::Parker;
 use crate::sys_common::{AsInner, IntoInner};
 use crate::time::{Duration, Instant};
@@ -468,7 +469,23 @@ impl Builder {
     {
         let Builder { name, stack_size } = self;
 
-        let stack_size = stack_size.unwrap_or_else(thread::min_stack);
+        let stack_size = stack_size.unwrap_or_else(|| {
+            static MIN: AtomicUsize = AtomicUsize::new(0);
+
+            match MIN.load(Ordering::Relaxed) {
+                0 => {}
+                n => return n - 1,
+            }
+
+            let amt = env::var_os("RUST_MIN_STACK")
+                .and_then(|s| s.to_str().and_then(|s| s.parse().ok()))
+                .unwrap_or(imp::DEFAULT_MIN_STACK_SIZE);
+
+            // 0 is our sentinel value, so ensure that we'll never see 0 after
+            // initialization has run
+            MIN.store(amt + 1, Ordering::Relaxed);
+            amt
+        });
 
         let my_thread = Thread::new(name.map(|name| {
             CString::new(name).expect("thread name may not contain interior null bytes")
@@ -1191,17 +1208,17 @@ impl ThreadId {
 
         cfg_if::cfg_if! {
             if #[cfg(target_has_atomic = "64")] {
-                use crate::sync::atomic::{AtomicU64, Ordering::Relaxed};
+                use crate::sync::atomic::AtomicU64;
 
                 static COUNTER: AtomicU64 = AtomicU64::new(0);
 
-                let mut last = COUNTER.load(Relaxed);
+                let mut last = COUNTER.load(Ordering::Relaxed);
                 loop {
                     let Some(id) = last.checked_add(1) else {
                         exhausted();
                     };
 
-                    match COUNTER.compare_exchange_weak(last, id, Relaxed, Relaxed) {
+                    match COUNTER.compare_exchange_weak(last, id, Ordering::Relaxed, Ordering::Relaxed) {
                         Ok(_) => return ThreadId(NonZero::new(id).unwrap()),
                         Err(id) => last = id,
                     }