From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 library/std/src/sys/windows/locks/mutex.rs | 57 ++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 library/std/src/sys/windows/locks/mutex.rs

(limited to 'library/std/src/sys/windows/locks/mutex.rs')

diff --git a/library/std/src/sys/windows/locks/mutex.rs b/library/std/src/sys/windows/locks/mutex.rs
new file mode 100644
index 000000000..f91e8f9f5
--- /dev/null
+++ b/library/std/src/sys/windows/locks/mutex.rs
@@ -0,0 +1,57 @@
+//! System Mutexes
+//!
+//! The Windows implementation of mutexes is a little odd and it might not be
+//! immediately obvious what's going on. The primary oddness is that SRWLock is
+//! used instead of CriticalSection, and this is done because:
+//!
+//! 1. SRWLock is several times faster than CriticalSection according to
+//!    benchmarks performed on both Windows 8 and Windows 7.
+//!
+//! 2. CriticalSection allows recursive locking while SRWLock deadlocks. The
+//!    Unix implementation deadlocks so consistency is preferred. See #19962 for
+//!    more details.
+//!
+//! 3. While CriticalSection is fair and SRWLock is not, the current Rust policy
+//!    is that there are no guarantees of fairness.
+
+use crate::cell::UnsafeCell;
+use crate::sys::c;
+
+pub struct Mutex {
+    srwlock: UnsafeCell<c::SRWLOCK>,
+}
+
+// Windows SRW Locks are movable (while not borrowed).
+pub type MovableMutex = Mutex;
+
+unsafe impl Send for Mutex {}
+unsafe impl Sync for Mutex {}
+
+#[inline]
+pub unsafe fn raw(m: &Mutex) -> c::PSRWLOCK {
+    m.srwlock.get()
+}
+
+impl Mutex {
+    #[inline]
+    pub const fn new() -> Mutex {
+        Mutex { srwlock: UnsafeCell::new(c::SRWLOCK_INIT) }
+    }
+    #[inline]
+    pub unsafe fn init(&mut self) {}
+
+    #[inline]
+    pub unsafe fn lock(&self) {
+        c::AcquireSRWLockExclusive(raw(self));
+    }
+
+    #[inline]
+    pub unsafe fn try_lock(&self) -> bool {
+        c::TryAcquireSRWLockExclusive(raw(self)) != 0
+    }
+
+    #[inline]
+    pub unsafe fn unlock(&self) {
+        c::ReleaseSRWLockExclusive(raw(self));
+    }
+}
-- 
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