fix: do not acquire filesys_lock for tell and seek

src/threads/thread.c

@@ -71,7 +71,7 @@ static void kernel_thread (thread_func *, void *aux);
 static void idle (void *aux UNUSED);
 static struct thread *running_thread (void);
 static struct thread *next_thread_to_run (void);
-static void init_process_result (struct thread *t);
+static bool init_process_result (struct thread *t);
 static void init_thread (struct thread *, const char *name, int nice,
                          int priority, fp32_t recent_cpu);
 static bool is_thread (struct thread *) UNUSED;
@@ -252,7 +252,11 @@ thread_create (const char *name, int priority,
   struct thread *parent_thread = thread_current ();
   init_thread (t, name, parent_thread->nice, priority, parent_thread->recent_cpu);
   tid = t->tid = allocate_tid ();
-  init_process_result (t);
+  if (!init_process_result (t))
+    {
+      palloc_free_page (t);
+      return TID_ERROR;
+    }
 
 #ifdef USERPROG
   /* Initialize the thread's file descriptor table. */
@@ -668,15 +672,18 @@ is_thread (struct thread *t)
 }
 
 /* Allocate and initialise a process result for given thread. */
-static void
+static bool
 init_process_result (struct thread *t)
 {
   struct process_result *result = malloc (sizeof (struct process_result));
+  if (result == NULL)
+    return false;
   result->tid = t->tid;
   result->exit_status = -1;
   lock_init (&result->lock);
   sema_init (&result->sema, 0);
   t->result = result;
+  return true;
 }
 
 /* Does basic initialization of T as a blocked thread named

src/userprog/syscall.c

@@ -348,12 +348,7 @@ syscall_seek (int fd, unsigned position)
   /* Find the file from the FD. If it does not exist, do nothing. */
   struct open_file *file_info = fd_get_file (fd);
   if (file_info != NULL)
-  {
-    /* File exists: Acquire the file system lock to prevent race conditions. */
-    lock_acquire (&filesys_lock);
     file_seek (file_info->file, position);
-    lock_release (&filesys_lock);
-  }
 }
 
 /* Handles the syscall for returning the next byte in a file referenced by
@@ -367,10 +362,7 @@ syscall_tell (int fd)
   if (file_info == NULL)
     return 0;
 
-  /* Acquire the file system lock to prevent race conditions. */
-  lock_acquire (&filesys_lock);
   unsigned pos = file_tell (file_info->file);
-  lock_release (&filesys_lock);
 
   /* Return the current position in the file. */
   return pos;