Kernel: reparent child processes to PID 1 when their parent exits

apps/src/init.c

@@ -163,24 +163,30 @@ int main()
     }
     if (child == 0)
     {
-        sleep(2);
+        sleep(1);
+        pid_t child = fork();
         printf("I am the child (PID %ld), my parent is PID %ld!!\n", getpid(), getppid());
-        execv("/bin/sym", NULL);
+        if (child) execv("/bin/sym", NULL);
+        else
+            execv("/bin/init", NULL);
         perror("execv");
         return 1;
     }
     else { printf("Success!! Got PID %ld\n", child); }
 
     int status;
-    pid_t result;
-    while ((result = waitpid(child, &status, 0)) == 0) // Child has not yet exited
+    for (;;)
     {
-        msleep(100);
+        pid_t result;
+        while ((result = wait(&status)) == 0) // No child has exited yet
+        {
+            msleep(100);
+        }
+        if (result < 0)
+        {
+            perror("wait");
+            return 1;
+        }
+        if (WIFEXITED(status)) { printf("Child process %ld exited with code %d\n", result, WEXITSTATUS(status)); }
     }
-    if (result < 0)
-    {
-        perror("waitpid");
-        return 1;
-    }
-    if (WIFEXITED(status)) { printf("Child process %ld exited with code %d\n", result, WEXITSTATUS(status)); }
 }

kernel/src/thread/Scheduler.cpp

@@ -45,6 +45,14 @@ template <typename Callback> void sched_for_each_task(Callback callback)
     } while (task != base_task);
 }
 
+template <typename Callback> void sched_for_each_child(Task* task, Callback callback)
+{
+    sched_for_each_task([&](Task* child) {
+        if (child->ppid == task->id) { return callback(child); }
+        return true;
+    });
+}
+
 Task* Scheduler::find_by_pid(uint64_t pid)
 {
     Task* result = nullptr;
@@ -265,6 +273,13 @@ void Scheduler::task_exit(Context* context, int64_t status)
     else
         sched_current_task->state = sched_current_task->Dying;
     sched_current_task->exit_status = status;
+    if (sched_current_task->id != 1)
+    {
+        sched_for_each_child(sched_current_task, [](Task* child) {
+            if (child->state != child->Exited) child->ppid = 1;
+            return true;
+        });
+    }
     task_yield(context);
 }
 
@@ -431,8 +446,8 @@ void sys_waitpid(Context* context, long pid, int* wstatus,
     Task* child = nullptr;
     if (pid == -1)
     {
-        sched_for_each_task([&](Task* task) {
-            if (task->state == task->Dying && task->ppid == sched_current_task->id)
+        sched_for_each_child(sched_current_task, [&](Task* task) {
+            if (task->state == task->Dying)
             {
                 child = task;
                 return false;