From 218caa410aa38c29984be31a5229b9fa717560ee Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:19:13 +0200
Subject: Merging upstream version 1.68.2+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 library/std/src/sys_common/thread_parker/futex.rs | 97 -----------------------
 1 file changed, 97 deletions(-)
 delete mode 100644 library/std/src/sys_common/thread_parker/futex.rs

(limited to 'library/std/src/sys_common/thread_parker/futex.rs')

diff --git a/library/std/src/sys_common/thread_parker/futex.rs b/library/std/src/sys_common/thread_parker/futex.rs
deleted file mode 100644
index d9e2f39e3..000000000
--- a/library/std/src/sys_common/thread_parker/futex.rs
+++ /dev/null
@@ -1,97 +0,0 @@
-use crate::pin::Pin;
-use crate::sync::atomic::AtomicU32;
-use crate::sync::atomic::Ordering::{Acquire, Release};
-use crate::sys::futex::{futex_wait, futex_wake};
-use crate::time::Duration;
-
-const PARKED: u32 = u32::MAX;
-const EMPTY: u32 = 0;
-const NOTIFIED: u32 = 1;
-
-pub struct Parker {
-    state: AtomicU32,
-}
-
-// Notes about memory ordering:
-//
-// Memory ordering is only relevant for the relative ordering of operations
-// between different variables. Even Ordering::Relaxed guarantees a
-// monotonic/consistent order when looking at just a single atomic variable.
-//
-// So, since this parker is just a single atomic variable, we only need to look
-// at the ordering guarantees we need to provide to the 'outside world'.
-//
-// The only memory ordering guarantee that parking and unparking provide, is
-// that things which happened before unpark() are visible on the thread
-// returning from park() afterwards. Otherwise, it was effectively unparked
-// before unpark() was called while still consuming the 'token'.
-//
-// In other words, unpark() needs to synchronize with the part of park() that
-// consumes the token and returns.
-//
-// This is done with a release-acquire synchronization, by using
-// Ordering::Release when writing NOTIFIED (the 'token') in unpark(), and using
-// Ordering::Acquire when checking for this state in park().
-impl Parker {
-    /// Construct the futex parker. The UNIX parker implementation
-    /// requires this to happen in-place.
-    pub unsafe fn new(parker: *mut Parker) {
-        parker.write(Self { state: AtomicU32::new(EMPTY) });
-    }
-
-    // Assumes this is only called by the thread that owns the Parker,
-    // which means that `self.state != PARKED`.
-    pub unsafe fn park(self: Pin<&Self>) {
-        // Change NOTIFIED=>EMPTY or EMPTY=>PARKED, and directly return in the
-        // first case.
-        if self.state.fetch_sub(1, Acquire) == NOTIFIED {
-            return;
-        }
-        loop {
-            // Wait for something to happen, assuming it's still set to PARKED.
-            futex_wait(&self.state, PARKED, None);
-            // Change NOTIFIED=>EMPTY and return in that case.
-            if self.state.compare_exchange(NOTIFIED, EMPTY, Acquire, Acquire).is_ok() {
-                return;
-            } else {
-                // Spurious wake up. We loop to try again.
-            }
-        }
-    }
-
-    // Assumes this is only called by the thread that owns the Parker,
-    // which means that `self.state != PARKED`. This implementation doesn't
-    // require `Pin`, but other implementations do.
-    pub unsafe fn park_timeout(self: Pin<&Self>, timeout: Duration) {
-        // Change NOTIFIED=>EMPTY or EMPTY=>PARKED, and directly return in the
-        // first case.
-        if self.state.fetch_sub(1, Acquire) == NOTIFIED {
-            return;
-        }
-        // Wait for something to happen, assuming it's still set to PARKED.
-        futex_wait(&self.state, PARKED, Some(timeout));
-        // This is not just a store, because we need to establish a
-        // release-acquire ordering with unpark().
-        if self.state.swap(EMPTY, Acquire) == NOTIFIED {
-            // Woke up because of unpark().
-        } else {
-            // Timeout or spurious wake up.
-            // We return either way, because we can't easily tell if it was the
-            // timeout or not.
-        }
-    }
-
-    // This implementation doesn't require `Pin`, but other implementations do.
-    #[inline]
-    pub fn unpark(self: Pin<&Self>) {
-        // Change PARKED=>NOTIFIED, EMPTY=>NOTIFIED, or NOTIFIED=>NOTIFIED, and
-        // wake the thread in the first case.
-        //
-        // Note that even NOTIFIED=>NOTIFIED results in a write. This is on
-        // purpose, to make sure every unpark() has a release-acquire ordering
-        // with park().
-        if self.state.swap(NOTIFIED, Release) == PARKED {
-            futex_wake(&self.state);
-        }
-    }
-}
-- 
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