Auto merge of #121956 - ChrisDenton:srwlock, r=joboet

Windows: Implement condvar, mutex and rwlock using futex

Well, the Windows equivalent: [`WaitOnAddress`,](https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-waitonaddress) [`WakeByAddressSingle`](https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-wakebyaddresssingle) and [`WakeByAddressAll`](https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-wakebyaddressall).

Note that Windows flavoured futexes can be different sizes (1, 2, 4 or 8 bytes). I took advantage of that in the `Mutex` implementation.

I also edited the Mutex implementation a bit more than necessary. I was having trouble keeping in my head what 0, 1 and 2 meant so I replaced them with consts.

I *think* we're maybe spinning a bit much. `WaitOnAddress` seems to be looping quite a bit too. But for now I've keep the implementations the same. I do wonder if it'd be worth reducing or removing our spinning on Windows.

This also adds a new shim to miri, because of course it does.

Fixes #121949

2 files changed, 21 insertions, 0 deletions

diff --git a/src/tools/miri/src/shims/windows/foreign_items.rs b/src/tools/miri/src/shims/windows/foreign_items.rs
index 734737a86dd..f56ea06dbe3 100644
--- a/src/tools/miri/src/shims/windows/foreign_items.rs
+++ b/src/tools/miri/src/shims/windows/foreign_items.rs
@@ -366,6 +366,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
                 this.WakeByAddressSingle(ptr_op)?;
             }
+            "WakeByAddressAll" => {
+                let [ptr_op] =
+                    this.check_shim(abi, Abi::System { unwind: false }, link_name, args)?;
+
+                this.WakeByAddressAll(ptr_op)?;
+            }
 
             // Dynamic symbol loading
             "GetProcAddress" => {
diff --git a/src/tools/miri/src/shims/windows/sync.rs b/src/tools/miri/src/shims/windows/sync.rs
index 2b9801fea68..1ce385aaaba 100644
--- a/src/tools/miri/src/shims/windows/sync.rs
+++ b/src/tools/miri/src/shims/windows/sync.rs
@@ -384,6 +384,21 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
         Ok(())
     }
+    fn WakeByAddressAll(&mut self, ptr_op: &OpTy<'tcx, Provenance>) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+
+        let ptr = this.read_pointer(ptr_op)?;
+
+        // See the Linux futex implementation for why this fence exists.
+        this.atomic_fence(AtomicFenceOrd::SeqCst)?;
+
+        while let Some(thread) = this.futex_wake(ptr.addr().bytes(), u32::MAX) {
+            this.unblock_thread(thread);
+            this.unregister_timeout_callback_if_exists(thread);
+        }
+
+        Ok(())
+    }
 
     fn SleepConditionVariableSRW(
         &mut self,