diff --git a/Mutex&Semaphore.pdf b/Mutex&Semaphore.pdf
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diff --git a/Mutex.kt b/Mutex.kt
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+++ b/Mutex.kt
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+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
+import kotlinx.coroutines.withContext
+import kotlin.system.measureTimeMillis
+
+suspend fun massiveRun(action: suspend () -> Unit) {
+    val n = 100  // number of coroutines to launch
+    val k = 1000 // times an action is repeated by each coroutine
+    val time = measureTimeMillis {
+        coroutineScope { // scope for coroutines
+            repeat(n) {
+                launch {
+                    repeat(k) { action() }
+                }
+            }
+        }
+    }
+    println("Completed ${n * k} actions in $time ms")
+}
+
+var counter = 0
+
+fun withoutMutex() = runBlocking {
+    withContext(Dispatchers.Default) {
+        massiveRun {
+            counter++
+        }
+    }
+    println("Counter = $counter")
+}
+
+val mutex = Mutex()
+suspend fun x() {
+    mutex.lock() //suspends until mutex is unlocked
+    mutex.tryLock() //returns false if mutex is locked
+    mutex.unlock() //unlocks mutex
+    mutex.withLock {
+
+    }
+}
+
+fun withMutex() = runBlocking {
+    withContext(Dispatchers.Default) {
+        massiveRun {
+            mutex.withLock {
+                var c = counter
+                c +=1;
+                counter = c
+            }
+        }
+    }
+    println("Counter = $counter")
+}
+
+fun main() {
+    withoutMutex()
+    //withMutex()
+}
diff --git a/Semaphore.kt b/Semaphore.kt
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+import kotlinx.coroutines.sync.Semaphore
+import kotlinx.coroutines.sync.withPermit
+
+val semaphore = Semaphore(5, 5)
+
+suspend fun main() {
+    semaphore.acquire() //reduces available permits, suspends when none available
+    semaphore.tryAcquire() //returns False if no permit available
+    semaphore.release() //releases permit, possible after acquire
+
+    semaphore.withPermit {
+
+    }
+}