From 77fedd6666e99e53d2964e69aa7d48771cd2e2e1 Mon Sep 17 00:00:00 2001
From: Gleb Koval <gleb@koval.net>
Date: Fri, 6 Dec 2024 17:31:33 +0000
Subject: [PATCH] fix: synchronise threads' SPTs with locks

---
 src/threads/thread.c   | 2 ++
 src/threads/thread.h   | 1 +
 src/userprog/process.c | 2 ++
 src/vm/page.c          | 9 ++++++++-
 4 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/threads/thread.c b/src/threads/thread.c
index 5af7da3..92bb940 100644
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -736,6 +736,8 @@ init_thread (struct thread *t, const char *name, int nice, int priority,
   t->recent_cpu = recent_cpu;
   t->priority = t->base_priority;
 
+  lock_init (&t->pages_lock);
+
   old_level = intr_disable ();
   list_push_back (&all_list, &t->allelem);
   intr_set_level (old_level);
diff --git a/src/threads/thread.h b/src/threads/thread.h
index fe7f362..ca461cd 100644
--- a/src/threads/thread.h
+++ b/src/threads/thread.h
@@ -136,6 +136,7 @@ struct thread
     struct list_elem elem;              /* List element. */
 
     struct hash pages;                  /* Table of open user pages. */
+    struct lock pages_lock; /* Lock for the supplementary page table. */
 
     /* Memory mapped files for user virtual memory. */
     struct hash mmap_files;             /* List of memory mapped files. */
diff --git a/src/userprog/process.c b/src/userprog/process.c
index 9024540..8fa2d27 100644
--- a/src/userprog/process.c
+++ b/src/userprog/process.c
@@ -371,7 +371,9 @@ process_exit (void)
   hash_destroy (&cur->open_files, fd_cleanup);
 
   /* Clean up the thread's supplemental page table. */
+  lock_acquire (&cur->pages_lock);
   hash_destroy (&cur->pages, page_cleanup);
+  lock_release (&cur->pages_lock);
 
   /* Close the executable file, implicitly allowing it to be written to. */
   if (cur->exec_file != NULL)
diff --git a/src/vm/page.c b/src/vm/page.c
index cea753a..487103d 100644
--- a/src/vm/page.c
+++ b/src/vm/page.c
@@ -90,6 +90,7 @@ page_insert_swapped (void *upage, void *kpage, struct list *owners)
 
       /* 1. Initialize swapped page entry. */
       struct page_entry *page = page_get (owner, upage);
+      lock_acquire (&owner->pages_lock);
       if (page == NULL)
         {
           page = malloc (sizeof (struct page_entry));
@@ -113,6 +114,7 @@ page_insert_swapped (void *upage, void *kpage, struct list *owners)
       page_set_swap (owner, pte, swap_slot);
 
       lock_release (&page->lock);
+      lock_release (&owner->pages_lock);
     }
   if (exec_file != NULL)
     {
@@ -155,7 +157,10 @@ page_insert_file (struct file *file, off_t ofs, void *upage,
   page->writable = writable;
   lock_init (&page->lock);
 
-  hash_insert (&thread_current ()->pages, &page->elem);
+  struct thread *t = thread_current ();
+  lock_acquire (&t->pages_lock);
+  hash_insert (&t->pages, &page->elem);
+  lock_release (&t->pages_lock);
   return page;
 }
 
@@ -167,8 +172,10 @@ page_get (struct thread *thread, void *upage)
   struct page_entry fake_page_entry;
   fake_page_entry.upage = upage;
 
+  lock_acquire (&thread->pages_lock);
   struct hash_elem *e
     = hash_find (&thread->pages, &fake_page_entry.elem);
+  lock_release (&thread->pages_lock);
   if (e == NULL)
       return NULL;
 
-- 
2.49.1