Update MentOs code to the latest development version.

programs/tests/t_kill.c

@@ -0,0 +1,66 @@
+///                MentOS, The Mentoring Operating system project
+/// @file t_kill.c
+/// @brief
+/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+#include <sys/unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <strerror.h>
+#include <sys/wait.h>
+
+#define cpu_relax() asm volatile("pause\n" \
+                                 :         \
+                                 :         \
+                                 : "memory")
+
+static inline void fake_sleep(int times)
+{
+    for (int j = 0; j < times; ++j)
+        for (long i = 1; i < 1024000; ++i)
+            cpu_relax();
+}
+
+void child_sigusr1_handler(int sig)
+{
+    printf("handler(sig: %d) : Starting handler (pid: %d).\n", sig, getpid());
+    printf("handler(sig: %d) : Ending handler (pid: %d).\n", sig, getpid());
+}
+
+void child_process()
+{
+    while (1) {
+        printf("I'm the child (%d): I'm playing around!\n", getpid());
+        fake_sleep(1);
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    printf("main : Creating child!\n");
+    pid_t ppid;
+    if ((ppid = fork()) == 0) {
+        printf("I'm the child (%d)!\n", ppid);
+        sigaction_t action;
+        memset(&action, 0, sizeof(action));
+        action.sa_handler = child_sigusr1_handler;
+        if (sigaction(SIGUSR1, &action, NULL) == -1) {
+            printf("Failed to set signal handler (%s).\n", SIGUSR1, strerror(errno));
+            return 1;
+        }
+        child_process();
+    } else {
+        printf("I'm the parent (%d)!\n", ppid);
+    }
+    fake_sleep(9);
+    kill(ppid, SIGUSR1);
+    fake_sleep(9);
+    kill(ppid, SIGTERM);
+    int status;
+    wait(&status);
+    printf("main : end (%d)\n", status);
+    return 0;
+}