diff --git a/chp5_synchronize/cancel_threads_semaphore/.gitignore b/chp5_synchronize/cancel_threads_semaphore/.gitignore
new file mode 100644
index 0000000..521eceb
--- /dev/null
+++ b/chp5_synchronize/cancel_threads_semaphore/.gitignore
@@ -0,0 +1 @@
+cancel_threads
\ No newline at end of file
diff --git a/chp5_synchronize/cancel_threads_semaphore/Makefile b/chp5_synchronize/cancel_threads_semaphore/Makefile
new file mode 100644
index 0000000..acdedb8
--- /dev/null
+++ b/chp5_synchronize/cancel_threads_semaphore/Makefile
@@ -0,0 +1,18 @@
+CC=gcc
+CFLAGS=-o cancel_threads -Wall -lpthread -lrt
+SRCS=main.c
+
+.DEFAULT_GOAL := build
+
+build:
+	$(CC) $(CFLAGS) -fsanitize=address -static-libasan $(SRCS)
+	
+release:
+	$(CC) $(CFLAGS) $(SRCS)
+
+debug:
+	$(CC) $(CFLAGS) -fsanitize=address -static-libasan -ggdb $(SRCS)
+	gdb -q cancel_threads
+
+clean:
+	rm -f cancel_threads
diff --git a/chp5_synchronize/cancel_threads_semaphore/main.c b/chp5_synchronize/cancel_threads_semaphore/main.c
new file mode 100644
index 0000000..34c31ec
--- /dev/null
+++ b/chp5_synchronize/cancel_threads_semaphore/main.c
@@ -0,0 +1,54 @@
+#include <pthread.h>
+#include <semaphore.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#define THREAD_COUNT 10
+
+void *expensive_task(void *);
+
+sem_t semaphore;
+
+int main(void) {
+
+  sem_init(&semaphore, 0, 0);
+
+  pthread_attr_t attr;
+  if (pthread_attr_init(&attr) != 0) {
+    perror("Error");
+    return EXIT_FAILURE;
+  }
+
+  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+
+  int n[THREAD_COUNT];
+  pthread_t threads[THREAD_COUNT];
+  for (int i = 0; i < THREAD_COUNT; i++) {
+    n[i] = i;
+    printf("Create thread number %d\n", i);
+    pthread_create(&threads[i], &attr, expensive_task, (void *)&n[i]);
+  }
+
+  printf("Waiting semaphore...\n");
+  sem_wait(&semaphore);
+  printf("Unlock semaphore\n");
+
+  for (int i = 0; i < THREAD_COUNT; i++) {
+    printf("Cancel thread %d\n", i);
+    pthread_cancel(threads[i]);
+  }
+
+  sem_destroy(&semaphore);
+
+  return EXIT_SUCCESS;
+}
+
+void *expensive_task(void *args) {
+  const int tid = *((int *)args);
+  printf("Thread %d are running...\n", tid);
+  sleep(rand() % 31);
+  printf("Thread %d terminated!!!\n", tid);
+  sem_post(&semaphore);
+  pthread_exit(0);
+}