Move Process to storing Threads in a linked list.

This should really be a vector or hashmap of some sort but this is fine
for now.

zion/lib/linked_list.h

@@ -76,6 +76,10 @@ class LinkedList {
     Iterator(ListItem* item) : item_(item) {}
 
     Iterator next() { return {item_->next}; }
+    Iterator& operator++() {
+      item_ = item_->next;
+      return *this;
+    }
 
     T& operator*() { return item_->item; }
     T& operator->() { return item_->item; }

zion/scheduler/process.cpp

@@ -16,10 +16,7 @@ Process* Process::RootProcess() {
   uint64_t pml4_addr = 0;
   asm volatile("mov %%cr3, %0;" : "=r"(pml4_addr));
   Process* proc = new Process(0, pml4_addr);
-  proc->thread_list_front_ = new ThreadEntry{
-      .thread = Thread::RootThread(proc),
-      .next = nullptr,
-  };
+  proc->threads_.PushBack(Thread::RootThread(proc));
   proc->next_thread_id_ = 1;
 
   return proc;
@@ -33,42 +30,29 @@ Process::Process(uint64_t elf_ptr) : id_(gNextId++), state_(RUNNING) {
 
 void Process::CreateThread(uint64_t elf_ptr) {
   Thread* thread = new Thread(this, next_thread_id_++, elf_ptr);
-  ThreadEntry* tentry = new ThreadEntry{
-      .thread = thread,
-      .next = nullptr,
-  };
-
-  if (thread_list_front_ == nullptr) {
-    thread_list_front_ = tentry;
-  } else {
-    ThreadEntry* entry = thread_list_front_;
-    while (entry->next != nullptr) {
-      entry = entry->next;
-    }
-    entry->next = tentry;
-  }
+  threads_.PushBack(thread);
   sched::EnqueueThread(thread);
 }
 
 Thread* Process::GetThread(uint64_t tid) {
-  ThreadEntry* entry = thread_list_front_;
-  while (entry != nullptr) {
-    if (entry->thread->tid() == tid) {
-      return entry->thread;
+  auto iter = threads_.begin();
+  while (iter != threads_.end()) {
+    if (iter->tid() == tid) {
+      return *iter;
     }
+    ++iter;
   }
   panic("Bad thread access.");
   return nullptr;
 }
 
 void Process::CheckState() {
-  ThreadEntry* entry = thread_list_front_;
-
-  while (entry != nullptr) {
-    if (entry->thread->GetState() != Thread::FINISHED) {
+  auto iter = threads_.begin();
+  while (iter != threads_.end()) {
+    if (iter->GetState() != Thread::FINISHED) {
       return;
     }
-    entry = entry->next;
+    ++iter;
   }
   state_ = FINISHED;
 }

zion/scheduler/process.h

@@ -2,6 +2,8 @@
 
 #include <stdint.h>
 
+#include "lib/linked_list.h"
+
 // Forward decl due to cyclic dependency.
 class Thread;
 
@@ -37,10 +39,5 @@ class Process {
 
   uint64_t next_thread_id_ = 0;
 
-  // FIXME: Make a better data structure for this.
-  struct ThreadEntry {
-    Thread* thread;
-    ThreadEntry* next;
-  };
-  ThreadEntry* thread_list_front_;
+  LinkedList<Thread*> threads_;
 };

zion/scheduler/scheduler.cpp

@@ -13,7 +13,7 @@ void DumpProcessStates(LinkedList<Process*>& proc_list) {
   auto iter = proc_list.begin();
   while (iter != proc_list.end()) {
     dbgln("%u: %u", iter->id(), iter->GetState());
-    iter = iter.next();
+    ++iter;
   }
 }