feat(lab2): unix lab2 done

Lab 2 is in fact the first lab in the set of ones we actually do. It's
not particularly hard, but consumed some time for me

OSs/lab2/unix/part-B/main.c

@@ -0,0 +1,53 @@
+/*
+ * "THE CHEESE-WARE LICENSE" (Revision 1):
+ * <ElectronixTM> wrote this file. As long as you retain this notice
+ * you can do whatever you want with this stuff. If we meet some day,
+ * and you think this stuff is worth it, you can buy me some cheese
+ * in return
+ */
+
+#include <stdio.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <assert.h>
+
+volatile unsigned long long global = 0;
+
+#define NR_THREADS 4
+#define GLOBAL_STOP_VALUE 15
+
+pthread_t threads[NR_THREADS] = {0};
+
+void *thread_routine(void* args)
+{
+    size_t arg = *((size_t *) args);
+    // Так как на глобальном счетчике нет синхронизации,
+    // количество выводов в консоль можен не совпадать с
+    // GLOBAL_STOP_VALUE
+    while (global < GLOBAL_STOP_VALUE) {
+        printf("Hello from thread %lu\n", arg);
+        global += 1;
+        sleep(5);
+    }
+    pthread_exit(NULL);
+}
+
+int main()
+{
+    for (size_t i = 0; i < NR_THREADS; i++) {
+        size_t *arg = malloc(sizeof(*arg));
+        assert(arg);
+        *arg = i;
+        pthread_create(&threads[i], NULL, thread_routine, arg);
+    }
+
+    int ret;
+    for (size_t i = 0; i < NR_THREADS; i++) {
+        ret = pthread_join(threads[i], NULL);
+        if (ret) {
+            break;
+        }
+    }
+    return 0;
+}