diff --git a/OSs/lab4/part-1/Makefile b/OSs/lab4/part-1/Makefile
new file mode 100644
index 0000000..da8fa15
--- /dev/null
+++ b/OSs/lab4/part-1/Makefile
@@ -0,0 +1,12 @@
+targets = main
+all: $(targets)
+
+main: main.o
+	$(CC) -o $@ $^ $(CFLAGS)
+
+%.o: %.c
+	$(CC) -c $^ -o $@ $(CFLAGS)
+
+clean:
+	rm -f $(targets)
+	rm -f *.o
diff --git a/OSs/lab4/part-1/main b/OSs/lab4/part-1/main
new file mode 100755
index 0000000..0a5b58f
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diff --git a/OSs/lab4/part-1/main.c b/OSs/lab4/part-1/main.c
new file mode 100644
index 0000000..1f01b24
--- /dev/null
+++ b/OSs/lab4/part-1/main.c
@@ -0,0 +1,99 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+#include <time.h>
+#include <signal.h>
+#include <semaphore.h>
+#include <errno.h>
+
+enum events{
+    EVENT_VICTIM_THREAD_READY,
+    EVENT_PRINT_BUFFER_UPDATED,
+    EVENTS_NR
+};
+
+enum threads_roles {
+    ROLE_VICTIM,
+    ROLE_KILLER,
+    ROLE_PRINTER,
+    ROLES_NR
+};
+
+#define ERR_PTR(ret) ((void*)(long)ret)
+#define PRINTER_TIMEOUT_SECS 2
+
+#define PRINT_BUFF_SIZE 256
+static sem_t sems[EVENTS_NR];
+static pthread_t threads[ROLES_NR];
+static char print_buffer[PRINT_BUFF_SIZE];
+static volatile bool run = true;
+
+void sig_handler(int signal)
+{
+    snprintf(print_buffer, PRINT_BUFF_SIZE, "signal %d recieved", signal);
+    pthread_exit(ERR_PTR(sem_post(&sems[EVENT_PRINT_BUFFER_UPDATED])));
+}
+
+void *killer_thread(void* _)
+{
+    sigset_t ss;
+    sigemptyset(&ss);
+    sigaddset(&ss, SIGUSR1);
+    if (pthread_sigmask(SIG_BLOCK, &ss, NULL))
+        pthread_exit(ERR_PTR(-EFAULT));
+    int ret = sem_wait(&sems[EVENT_VICTIM_THREAD_READY]);
+    if (ret) pthread_exit(ERR_PTR(ret));
+    pthread_exit(ERR_PTR(pthread_kill(threads[ROLE_VICTIM], SIGUSR1)));
+}
+
+void *victim_thread(void* _)
+{
+    int ret = sem_post(&sems[EVENT_VICTIM_THREAD_READY]);
+    if (ret) pthread_exit(ERR_PTR(ret));
+    volatile int x = 0; // for compiler not to optimize infinite loop
+    while (run) {
+        x++;
+    }
+    pthread_exit(NULL);
+}
+
+void *printer_thread(void* _)
+{
+    sigset_t ss;
+    sigemptyset(&ss);
+    sigaddset(&ss, SIGUSR1);
+    if (pthread_sigmask(SIG_BLOCK, &ss, NULL)) pthread_exit(ERR_PTR(-EFAULT));
+    while (run) {
+        struct timespec ts = {0};
+        int ret = timespec_get(&ts, TIME_UTC);
+        if (ret != TIME_UTC) pthread_exit(ERR_PTR(-EFAULT));
+        ts.tv_sec += PRINTER_TIMEOUT_SECS;
+        if (sem_timedwait(&sems[EVENT_PRINT_BUFFER_UPDATED], &ts))
+            pthread_exit(ERR_PTR(-EFAULT));
+        puts(print_buffer);
+        memset(print_buffer, 0, PRINT_BUFF_SIZE);
+    }
+    pthread_exit(NULL);
+}
+
+#define DO_OR_FAIL(cond) if (cond) return EXIT_FAILURE
+
+int main()
+{
+    struct sigaction sa = {
+        .sa_handler = sig_handler,
+    };
+    DO_OR_FAIL(sigaction(SIGUSR1, &sa, NULL));
+    DO_OR_FAIL(sem_init(&sems[EVENT_VICTIM_THREAD_READY], 0, 0));
+    DO_OR_FAIL(sem_init(&sems[EVENT_PRINT_BUFFER_UPDATED], 0, 0));
+    DO_OR_FAIL(pthread_create(&threads[ROLE_KILLER], NULL, killer_thread, NULL));
+    DO_OR_FAIL(pthread_create(&threads[ROLE_PRINTER], NULL, printer_thread, NULL));
+    DO_OR_FAIL(pthread_create(&threads[ROLE_VICTIM], NULL, victim_thread, NULL));
+
+    for (size_t i = 0; i < ROLES_NR; i++) {
+        DO_OR_FAIL(pthread_join(threads[i], NULL));
+    }
+    return EXIT_SUCCESS;
+}
diff --git a/OSs/lab4/part-1/main.o b/OSs/lab4/part-1/main.o
new file mode 100644
index 0000000..e93bcf4
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