X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fsync%2Fmod.rs;h=1b2b9a739b8c5d3078204917f55b0fef86e87f13;hb=a9e6341f79af07aa9870d88e3887912fa2114e39;hp=5b0cc9c1886611bd0dc47a8d39188f36363b825a;hpb=9422370dd2b2ec73115b5950fa5e19db51c8ea73;p=rust-lightning

diff --git a/lightning/src/sync/mod.rs b/lightning/src/sync/mod.rs
index 5b0cc9c1..1b2b9a73 100644
--- a/lightning/src/sync/mod.rs
+++ b/lightning/src/sync/mod.rs
@@ -1,3 +1,25 @@
+#[allow(dead_code)] // Depending on the compilation flags some variants are never used
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) enum LockHeldState {
+	HeldByThread,
+	NotHeldByThread,
+	#[cfg(any(feature = "_bench_unstable", not(test)))]
+	Unsupported,
+}
+
+pub(crate) trait LockTestExt<'a> {
+	fn held_by_thread(&self) -> LockHeldState;
+	type ExclLock;
+	/// If two instances of the same mutex are being taken at the same time, it's very easy to have
+	/// a lockorder inversion and risk deadlock. Thus, we default to disabling such locks.
+	///
+	/// However, sometimes they cannot be avoided. In such cases, this method exists to take a
+	/// mutex while avoiding a test failure. It is deliberately verbose and includes the term
+	/// "unsafe" to indicate that special care needs to be taken to ensure no deadlocks are
+	/// possible.
+	fn unsafe_well_ordered_double_lock_self(&'a self) -> Self::ExclLock;
+}
+
 #[cfg(all(feature = "std", not(feature = "_bench_unstable"), test))]
 mod debug_sync;
 #[cfg(all(feature = "std", not(feature = "_bench_unstable"), test))]
@@ -11,6 +33,25 @@ pub(crate) mod fairrwlock;
 #[cfg(all(feature = "std", any(feature = "_bench_unstable", not(test))))]
 pub use {std::sync::{Arc, Mutex, Condvar, MutexGuard, RwLock, RwLockReadGuard, RwLockWriteGuard}, fairrwlock::FairRwLock};
 
+#[cfg(all(feature = "std", any(feature = "_bench_unstable", not(test))))]
+mod ext_impl {
+	use super::*;
+	impl<'a, T: 'a> LockTestExt<'a> for Mutex<T> {
+		#[inline]
+		fn held_by_thread(&self) -> LockHeldState { LockHeldState::Unsupported }
+		type ExclLock = MutexGuard<'a, T>;
+		#[inline]
+		fn unsafe_well_ordered_double_lock_self(&'a self) -> MutexGuard<T> { self.lock().unwrap() }
+	}
+	impl<'a, T: 'a> LockTestExt<'a> for RwLock<T> {
+		#[inline]
+		fn held_by_thread(&self) -> LockHeldState { LockHeldState::Unsupported }
+		type ExclLock = RwLockWriteGuard<'a, T>;
+		#[inline]
+		fn unsafe_well_ordered_double_lock_self(&'a self) -> RwLockWriteGuard<T> { self.write().unwrap() }
+	}
+}
+
 #[cfg(not(feature = "std"))]
 mod nostd_sync;
 #[cfg(not(feature = "std"))]