Avoid loosing track of processes

Due to the changes in ps_struct list tracking, we were inserting new
items in the middle of the list and leaving orphaned segments hanging
around. Avoid this by seeking to the end for inserting new ps_structs.

Author: codyps

src/store.c

@@ -258,11 +258,19 @@ int log_sample(DIR *proc,
                         char t[32];
                         struct ps_struct *parent;
 
-                        ps->next_ps = ps->next_running = new0(struct ps_struct, 1);
-                        if (!ps->next_ps)
+                        /* find the insertion point for the last item */
+                        struct ps_struct **ps_next = &ps->next_ps;
+                        while (*ps_next) {
+                                ps_next = &(*ps_next)->next_ps;
+                        }
+
+                        assert(!*ps_next);
+                        assert(!ps->next_running);
+                        *ps_next = ps->next_running = new0(struct ps_struct, 1);
+                        if (!*ps_next)
                                 return log_oom();
 
-                        ps = ps->next_ps;
+                        ps = *ps_next;
                         ps->pid = pid;
                         ps->sched = -1;
                         ps->schedstat = -1;