From 8afee1420232e9698aef020b35aff048b9a302e9 Mon Sep 17 00:00:00 2001
From: joboet <jonasboettiger@icloud.com>
Date: Thu, 11 Apr 2024 19:36:50 +0200
Subject: [PATCH] std: use queue-based `RwLock` on Xous

---
 library/std/src/sys/sync/rwlock/xous.rs | 74 -------------------------
 1 file changed, 74 deletions(-)
 delete mode 100644 library/std/src/sys/sync/rwlock/xous.rs

diff --git a/library/std/src/sys/sync/rwlock/xous.rs b/library/std/src/sys/sync/rwlock/xous.rs
deleted file mode 100644
index ab45b33e1f69..000000000000
--- a/library/std/src/sys/sync/rwlock/xous.rs
+++ /dev/null
@@ -1,74 +0,0 @@
-use crate::sync::atomic::{AtomicIsize, Ordering::Acquire};
-use crate::thread::yield_now;
-
-pub struct RwLock {
-    /// The "mode" value indicates how many threads are waiting on this
-    /// Mutex. Possible values are:
-    ///    -1: The lock is locked for writing
-    ///     0: The lock is unlocked
-    ///   >=1: The lock is locked for reading
-    ///
-    /// This currently spins waiting for the lock to be freed. An
-    /// optimization would be to involve the ticktimer server to
-    /// coordinate unlocks.
-    mode: AtomicIsize,
-}
-
-const RWLOCK_WRITING: isize = -1;
-const RWLOCK_FREE: isize = 0;
-
-unsafe impl Send for RwLock {}
-unsafe impl Sync for RwLock {}
-
-impl RwLock {
-    #[inline]
-    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
-    pub const fn new() -> RwLock {
-        RwLock { mode: AtomicIsize::new(RWLOCK_FREE) }
-    }
-
-    #[inline]
-    pub unsafe fn read(&self) {
-        while !unsafe { self.try_read() } {
-            yield_now();
-        }
-    }
-
-    #[inline]
-    pub unsafe fn try_read(&self) -> bool {
-        self.mode
-            .fetch_update(
-                Acquire,
-                Acquire,
-                |v| if v == RWLOCK_WRITING { None } else { Some(v + 1) },
-            )
-            .is_ok()
-    }
-
-    #[inline]
-    pub unsafe fn write(&self) {
-        while !unsafe { self.try_write() } {
-            yield_now();
-        }
-    }
-
-    #[inline]
-    pub unsafe fn try_write(&self) -> bool {
-        self.mode.compare_exchange(RWLOCK_FREE, RWLOCK_WRITING, Acquire, Acquire).is_ok()
-    }
-
-    #[inline]
-    pub unsafe fn read_unlock(&self) {
-        let previous = self.mode.fetch_sub(1, Acquire);
-        assert!(previous != RWLOCK_FREE);
-        assert!(previous != RWLOCK_WRITING);
-    }
-
-    #[inline]
-    pub unsafe fn write_unlock(&self) {
-        assert_eq!(
-            self.mode.compare_exchange(RWLOCK_WRITING, RWLOCK_FREE, Acquire, Acquire),
-            Ok(RWLOCK_WRITING)
-        );
-    }
-}