From b30f149dc93195a5d5744d031c30180ba768f00f Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Sat, 8 Oct 2022 10:57:59 -0400
Subject: [PATCH] Use mutex on iOS 15 instead of os_unfair_lock

See #178
---
 Tusker/MultiThreadDictionary.swift | 45 +++++++++++++++++++++---------
 TuskerTests/TuskerTests.swift      | 40 ++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 13 deletions(-)

diff --git a/Tusker/MultiThreadDictionary.swift b/Tusker/MultiThreadDictionary.swift
index 1a0d4661..8b5c316b 100644
--- a/Tusker/MultiThreadDictionary.swift
+++ b/Tusker/MultiThreadDictionary.swift
@@ -19,7 +19,7 @@ class MultiThreadDictionary<Key: Hashable & Sendable, Value: Sendable> {
         if #available(iOS 16.0, *) {
             self.lock = OSAllocatedUnfairLock(initialState: [:])
         } else {
-            self.lock = UnfairLock(initialState: [:])
+            self.lock = MutexLock(initialState: [:])
         }
     }
     
@@ -65,22 +65,41 @@ fileprivate protocol Lock<State> {
 extension OSAllocatedUnfairLock: Lock {
 }
 
-// from http://www.russbishop.net/the-law
-fileprivate class UnfairLock<State>: Lock {
-    private var lock: UnsafeMutablePointer<os_unfair_lock>
+// something is wrong with the UnfairLock impl and it results in segv_accerrs 
+fileprivate class MutexLock<State>: Lock {
     private var state: State
+    private var lock = NSLock()
+    
     init(initialState: State) {
         self.state = initialState
-        self.lock = .allocate(capacity: 1)
-        self.lock.initialize(to: os_unfair_lock())
     }
-    deinit {
-        self.lock.deinitialize(count: 1)
-        self.lock.deallocate()
-    }
-    func withLock<R>(_ body: (inout State) throws -> R) rethrows -> R where R: Sendable {
-        os_unfair_lock_lock(lock)
-        defer { os_unfair_lock_unlock(lock) }
+    
+    func withLock<R>(_ body: @Sendable (inout State) throws -> R) rethrows -> R where R : Sendable {
+        if !lock.lock(before: Date(timeIntervalSinceNow: 1)) {
+            // if we can't acquire the lock after 1 second, something has gone catastrophically wrong
+            fatalError()
+        }
+        defer { lock.unlock() }
         return try body(&state)
     }
 }
+
+//// from http://www.russbishop.net/the-law
+//fileprivate class UnfairLock<State>: Lock {
+//    private var lock: UnsafeMutablePointer<os_unfair_lock>
+//    private var state: State
+//    init(initialState: State) {
+//        self.state = initialState
+//        self.lock = .allocate(capacity: 1)
+//        self.lock.initialize(to: os_unfair_lock())
+//    }
+//    deinit {
+//        self.lock.deinitialize(count: 1)
+//        self.lock.deallocate()
+//    }
+//    func withLock<R>(_ body: (inout State) throws -> R) rethrows -> R where R: Sendable {
+//        os_unfair_lock_lock(lock)
+//        defer { os_unfair_lock_unlock(lock) }
+//        return try body(&state)
+//    }
+//}
diff --git a/TuskerTests/TuskerTests.swift b/TuskerTests/TuskerTests.swift
index 1d8f9a78..2ba572fa 100644
--- a/TuskerTests/TuskerTests.swift
+++ b/TuskerTests/TuskerTests.swift
@@ -30,5 +30,45 @@ class TuskerTests: XCTestCase {
             // Put the code you want to measure the time of here.
         }
     }
+    
+    
+    func testFuckingLock() {
+        let lock = MutexLock<[Int: Bool]>(initialState: [:])
+        for i in 0..<100 {
+            Thread.detachNewThread {
+                for j in 0..<50_000 {
+                    lock.withLock {
+                        $0[i * 50_000 + j] = true
+                    }
+                }
+            }
+        }
+        while true {
+            if lock.withLock({ $0.count }) == 5_000_000 {
+                break
+            }
+        }
+        lock.withLock({ _ in
+            print("WHAT THE FUUUUUUUUUUUUCK")
+        })
+    }
 
 }
+
+fileprivate class MutexLock<State> {
+    private var state: State
+    private var lock = NSLock()
+    
+    init(initialState: State) {
+        self.state = initialState
+    }
+    
+    func withLock<R>(_ body: @Sendable (inout State) throws -> R) rethrows -> R where R : Sendable {
+        if !lock.lock(before: Date(timeIntervalSinceNow: 1)) {
+            // if we can't acquire the lock after 1 second, something has gone catastrophically wrong
+            fatalError()
+        }
+        defer { lock.unlock() }
+        return try body(&state)
+    }
+}