From 87f5bac435872c533f1744010954a5442d61c92a Mon Sep 17 00:00:00 2001
From: Marat Al <m.alekperov@gmail.com>
Date: Mon, 13 May 2024 02:11:59 +0200
Subject: [PATCH] Removed semaphore in favour of an atomic property for
 synchronised access.

---
 Source/ARTGCD.m | 34 ++++++++++++----------------------
 1 file changed, 12 insertions(+), 22 deletions(-)

diff --git a/Source/ARTGCD.m b/Source/ARTGCD.m
index 26a17eca9..55ff07286 100644
--- a/Source/ARTGCD.m
+++ b/Source/ARTGCD.m
@@ -1,8 +1,12 @@
 #import "ARTGCD.h"
 
+@interface ARTScheduledBlockHandle ()
+
+@property (atomic, copy, nullable) dispatch_block_t block;
+
+@end
+
 @implementation ARTScheduledBlockHandle {
-    dispatch_semaphore_t _semaphore;
-    dispatch_block_t _block;
     dispatch_block_t _scheduledBlock;
 }
 
@@ -11,21 +15,13 @@ - (instancetype)initWithDelay:(NSTimeInterval)delay queue:(dispatch_queue_t)queu
     if (self == nil)
         return nil;
 
-    // Use a sempaphore to coorindate state. We use a reference here to decouple it when creating a block we'll schedule.
-    dispatch_semaphore_t semaphore = dispatch_semaphore_create(1);
-
     __weak ARTScheduledBlockHandle *weakSelf = self;
     _scheduledBlock = dispatch_block_create(0, ^{
         dispatch_block_t copiedBlock = nil;
-        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
-        {
-            // Get a strong reference to self within our semaphore to avoid potential race conditions
-            ARTScheduledBlockHandle *strongSelf = weakSelf;
-            if (strongSelf != nil) {
-                copiedBlock = strongSelf->_block; // copied below
-            }
+        ARTScheduledBlockHandle *strongSelf = weakSelf;
+        if (strongSelf != nil) {
+            copiedBlock = strongSelf.block; // copied below
         }
-        dispatch_semaphore_signal(semaphore);
 
         // If our block is non-nil, our scheduled block was still valid by the time this was invoked
         if (copiedBlock != nil) {
@@ -33,8 +29,7 @@ - (instancetype)initWithDelay:(NSTimeInterval)delay queue:(dispatch_queue_t)queu
         }
     });
 
-    _block = [block copy];
-    _semaphore = semaphore;
+    self.block = block; // copied block
 
     dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(NSEC_PER_SEC * delay)), queue, _scheduledBlock);
 
@@ -42,13 +37,8 @@ - (instancetype)initWithDelay:(NSTimeInterval)delay queue:(dispatch_queue_t)queu
 }
 
 - (void)cancel {
-    // Cancel within our semaphore for predictable behavior if our block is invoked while we're cancelling
-    dispatch_semaphore_wait(_semaphore, DISPATCH_TIME_FOREVER);
-    {
-        dispatch_block_cancel(_scheduledBlock);
-        _block = nil;
-    }
-    dispatch_semaphore_signal(_semaphore);
+    self.block = nil;
+    dispatch_block_cancel(_scheduledBlock);
 }
 
 - (void)dealloc {