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>
---
 vendor/sharded-slab/src/tid.rs | 194 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 194 insertions(+)
 create mode 100644 vendor/sharded-slab/src/tid.rs

(limited to 'vendor/sharded-slab/src/tid.rs')

diff --git a/vendor/sharded-slab/src/tid.rs b/vendor/sharded-slab/src/tid.rs
new file mode 100644
index 000000000..57d64f970
--- /dev/null
+++ b/vendor/sharded-slab/src/tid.rs
@@ -0,0 +1,194 @@
+use crate::{
+    cfg::{self, CfgPrivate},
+    page,
+    sync::{
+        atomic::{AtomicUsize, Ordering},
+        lazy_static, thread_local, Mutex,
+    },
+    Pack,
+};
+use std::{
+    cell::{Cell, UnsafeCell},
+    collections::VecDeque,
+    fmt,
+    marker::PhantomData,
+    sync::PoisonError,
+};
+
+/// Uniquely identifies a thread.
+pub(crate) struct Tid<C> {
+    id: usize,
+    _not_send: PhantomData<UnsafeCell<()>>,
+    _cfg: PhantomData<fn(C)>,
+}
+
+#[derive(Debug)]
+struct Registration(Cell<Option<usize>>);
+
+struct Registry {
+    next: AtomicUsize,
+    free: Mutex<VecDeque<usize>>,
+}
+
+lazy_static! {
+    static ref REGISTRY: Registry = Registry {
+        next: AtomicUsize::new(0),
+        free: Mutex::new(VecDeque::new()),
+    };
+}
+
+thread_local! {
+    static REGISTRATION: Registration = Registration::new();
+}
+
+// === impl Tid ===
+
+impl<C: cfg::Config> Pack<C> for Tid<C> {
+    const LEN: usize = C::MAX_SHARDS.trailing_zeros() as usize + 1;
+
+    type Prev = page::Addr<C>;
+
+    #[inline(always)]
+    fn as_usize(&self) -> usize {
+        self.id
+    }
+
+    #[inline(always)]
+    fn from_usize(id: usize) -> Self {
+        Self {
+            id,
+            _not_send: PhantomData,
+            _cfg: PhantomData,
+        }
+    }
+}
+
+impl<C: cfg::Config> Tid<C> {
+    #[inline]
+    pub(crate) fn current() -> Self {
+        REGISTRATION
+            .try_with(Registration::current)
+            .unwrap_or_else(|_| Self::poisoned())
+    }
+
+    pub(crate) fn is_current(self) -> bool {
+        REGISTRATION
+            .try_with(|r| self == r.current::<C>())
+            .unwrap_or(false)
+    }
+
+    #[inline(always)]
+    pub fn new(id: usize) -> Self {
+        Self::from_usize(id)
+    }
+}
+
+impl<C> Tid<C> {
+    #[cold]
+    fn poisoned() -> Self {
+        Self {
+            id: std::usize::MAX,
+            _not_send: PhantomData,
+            _cfg: PhantomData,
+        }
+    }
+
+    /// Returns true if the local thread ID was accessed while unwinding.
+    pub(crate) fn is_poisoned(&self) -> bool {
+        self.id == std::usize::MAX
+    }
+}
+
+impl<C> fmt::Debug for Tid<C> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.is_poisoned() {
+            f.debug_tuple("Tid")
+                .field(&format_args!("<poisoned>"))
+                .finish()
+        } else {
+            f.debug_tuple("Tid")
+                .field(&format_args!("{}", self.id))
+                .finish()
+        }
+    }
+}
+
+impl<C> PartialEq for Tid<C> {
+    fn eq(&self, other: &Self) -> bool {
+        self.id == other.id
+    }
+}
+
+impl<C> Eq for Tid<C> {}
+
+impl<C: cfg::Config> Clone for Tid<C> {
+    fn clone(&self) -> Self {
+        Self::new(self.id)
+    }
+}
+
+impl<C: cfg::Config> Copy for Tid<C> {}
+
+// === impl Registration ===
+
+impl Registration {
+    fn new() -> Self {
+        Self(Cell::new(None))
+    }
+
+    #[inline(always)]
+    fn current<C: cfg::Config>(&self) -> Tid<C> {
+        if let Some(tid) = self.0.get().map(Tid::new) {
+            return tid;
+        }
+
+        self.register()
+    }
+
+    #[cold]
+    fn register<C: cfg::Config>(&self) -> Tid<C> {
+        let id = REGISTRY
+            .free
+            .lock()
+            .ok()
+            .and_then(|mut free| {
+                if free.len() > 1 {
+                    free.pop_front()
+                } else {
+                    None
+                }
+            })
+            .unwrap_or_else(|| {
+                let id = REGISTRY.next.fetch_add(1, Ordering::AcqRel);
+                if id > Tid::<C>::BITS {
+                    panic_in_drop!(
+                        "creating a new thread ID ({}) would exceed the \
+                        maximum number of thread ID bits specified in {} \
+                        ({})",
+                        id,
+                        std::any::type_name::<C>(),
+                        Tid::<C>::BITS,
+                    );
+                }
+                id
+            });
+
+        self.0.set(Some(id));
+        Tid::new(id)
+    }
+}
+
+// Reusing thread IDs doesn't work under loom, since this `Drop` impl results in
+// an access to a `loom` lazy_static while the test is shutting down, which
+// panics. T_T
+// Just skip TID reuse and use loom's lazy_static macro to ensure we have a
+// clean initial TID on every iteration, instead.
+#[cfg(not(all(loom, any(feature = "loom", test))))]
+impl Drop for Registration {
+    fn drop(&mut self) {
+        if let Some(id) = self.0.get() {
+            let mut free_list = REGISTRY.free.lock().unwrap_or_else(PoisonError::into_inner);
+            free_list.push_back(id);
+        }
+    }
+}
-- 
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