Merge branch 'task1/merged/priority-scheduling' into 'task1/priority-scheduling'

# Conflicts:
#   .gitignore
#   src/threads/synch.c
#   src/threads/thread.c

.gitignore

@@ -31,6 +31,3 @@
 *.nav
 *.toc
 
-#ignore files from CLion/VSCode IDEs
-.idea
-.vscode

.gitlab-ci.yml

@@ -1,44 +0,0 @@
-stages:
-  - test
-
-.pintos_tests:
-  stage: test
-  image: gitlab.doc.ic.ac.uk:4567/lab2425_autumn/pintos_22/pintos-testing:latest
-  artifacts:
-    when: always
-    paths:
-      - src/$DIR/build/tests/$DIR/
-  before_script:
-    - cd src/utils
-    - make
-    - export PATH=$PWD:$PATH
-    - cd ../..
-  script:
-    - cd src/$DIR
-    - make check | tee build.log
-    - grep -q "FAIL tests/$DIR" build.log && exit 1 || exit 0
-
-test_devices:
-  extends: .pintos_tests
-  variables:
-    DIR: devices
-
-test_filesys:
-  extends: .pintos_tests
-  variables:
-    DIR: filesys
-
-test_threads:
-  extends: .pintos_tests
-  variables:
-    DIR: threads
-
-test_userprog:
-  extends: .pintos_tests
-  variables:
-    DIR: userprog
-
-test_vm:
-  extends: .pintos_tests
-  variables:
-    DIR: vm

Dockerfile.devel

@@ -1,3 +0,0 @@
-FROM debian:12-slim
-
-RUN apt update && apt install gcc perl make qemu-system-i386 gdb -y

src/devices/timer.c

@@ -119,6 +119,9 @@ timer_sleep (int64_t ticks)
                        NULL);
   intr_set_level (old_level);
   sema_down (&st.semaphore);
+  old_level = intr_disable ();
+  list_remove (&st.elem);
+  intr_set_level (old_level);
 }
 
 /* Sleeps for approximately MS milliseconds.  Interrupts must be
@@ -201,10 +204,7 @@ timer_interrupt (struct intr_frame *args UNUSED)
     {
       struct asleep_thread *st = list_entry (e, struct asleep_thread, elem);
       if (ticks >= st->end_at)
-        {
+        sema_up (&st->semaphore);
-          list_remove (&st->elem);
-          sema_up (&st->semaphore);
-        }
       else
         break;
     }

src/filesys/file.h

@@ -4,9 +4,6 @@
 #include "filesys/off_t.h"
 #include <stdbool.h>
 
-/* The maximum length of a file name in PintOS. */
-#define FNAME_MAX_LEN 14
-
 struct inode;
 
 /* Opening and closing files. */

src/lib/user/syscall.c

@@ -166,7 +166,7 @@ mkdir (const char *dir)
 }
 
 bool
-readdir (int fd, char name[FNAME_MAX_LEN + 1]) 
+readdir (int fd, char name[READDIR_MAX_LEN + 1]) 
 {
   return syscall2 (SYS_READDIR, fd, name);
 }

src/lib/user/syscall.h

@@ -3,7 +3,6 @@
 
 #include <stdbool.h>
 #include <debug.h>
-#include "../../filesys/file.h"
 
 /* Process identifier. */
 typedef int pid_t;
@@ -13,6 +12,9 @@ typedef int pid_t;
 typedef int mapid_t;
 #define MAP_FAILED ((mapid_t) -1)
 
+/* Maximum characters in a filename written by readdir(). */
+#define READDIR_MAX_LEN 14
+
 /* Typical return values from main() and arguments to exit(). */
 #define EXIT_SUCCESS 0          /* Successful execution. */
 #define EXIT_FAILURE 1          /* Unsuccessful execution. */
@@ -39,7 +41,7 @@ void munmap (mapid_t);
 /* Task 4 only. */
 bool chdir (const char *dir);
 bool mkdir (const char *dir);
-bool readdir (int fd, char name[FNAME_MAX_LEN + 1]);
+bool readdir (int fd, char name[READDIR_MAX_LEN + 1]);
 bool isdir (int fd);
 int inumber (int fd);
 

src/threads/fixed-point.h

@@ -1,100 +0,0 @@
-#include <stdint.h>
-#ifndef FIXED_POINT_H
-#define FIXED_POINT_H
-
-typedef struct
-  {
-    int32_t raw;
-  } fp32_t;
-
-/* Fixed Point Arithmetic bit count constants */
-#define NUM_FRAC_BITS 14
-#define NUM_INT_BITS (31 - NUM_FRAC_BITS)
-#define CONVERSION_FACTOR (1 << NUM_FRAC_BITS) /* f = 2^q, (2^14) */
-
-/* Fixed Point Arithmetic conversion operations */
-/* Converts an integer n to a fixed point number */
-inline fp32_t
-fp_from_int (int32_t n)
-{
-  return (fp32_t){ n * CONVERSION_FACTOR };
-}
-
-/* Handles conversion of fixed point to integer,
-   with truncation */
-inline int32_t
-fp_floor (fp32_t x)
-{
-  return x.raw / CONVERSION_FACTOR;
-}
-
-/* Handles conversion of fixed point to integer,
-   with rounding */
-inline int32_t
-fp_round (fp32_t x)
-{
-  if (x.raw >= 0)
-    return (x.raw + CONVERSION_FACTOR / 2) / CONVERSION_FACTOR;
-  else
-    return (x.raw - CONVERSION_FACTOR / 2) / CONVERSION_FACTOR;
-}
-
-/* Add two fixed points */
-inline fp32_t
-fp_add (fp32_t x, fp32_t y)
-{
-  return (fp32_t){ x.raw + y.raw };
-}
-
-/* Subtract two fixed points */
-inline fp32_t
-fp_sub (fp32_t x, fp32_t y)
-{
-  return (fp32_t){ x.raw - y.raw };
-}
-
-
-
-/* Multiple two fixed points */
-inline fp32_t
-fp_mul (fp32_t x, fp32_t y)
-{
-  return (fp32_t){ ((int64_t)x.raw) * y.raw / CONVERSION_FACTOR };
-}
-
-/* Divide two fixed points */
-inline fp32_t
-fp_div (fp32_t x, fp32_t y)
-{
-  return (fp32_t){ ((int64_t)x.raw) * CONVERSION_FACTOR / y.raw };
-}
-
-/* Multiply fixed point and integer */
-inline fp32_t
-fp_mul_int (fp32_t x, int32_t n)
-{
-  return (fp32_t){ x.raw * n };
-}
-
-/* Divide fixed point by integer */
-inline fp32_t
-fp_div_int (fp32_t x, int32_t n)
-{
-  return (fp32_t){ x.raw / n };
-}
-
-/* Add fixed point to integer */
-inline fp32_t
-fp_add_int (fp32_t x, int32_t n)
-{
-  return (fp32_t){ x.raw + n * CONVERSION_FACTOR };
-}
-
-/* Subtract integer from fixed point */
-inline fp32_t
-fp_sub_int (fp32_t x, int32_t n)
-{
-  return (fp32_t){ x.raw - n * CONVERSION_FACTOR };
-}
-
-#endif //FIXED_POINT_H

src/threads/synch.c

@@ -32,10 +32,6 @@
 #include "threads/interrupt.h"
 #include "threads/thread.h"
 
-static bool
-priority_less (const struct list_elem *a_, const struct list_elem *b_,
-               void *aux UNUSED);
-
 /* Initializes semaphore SEMA to VALUE.  A semaphore is a
    nonnegative integer along with two atomic operators for
    manipulating it:
@@ -72,7 +68,8 @@ sema_down (struct semaphore *sema)
   old_level = intr_disable ();
   while (sema->value == 0) 
     {
-      list_push_back (&sema->waiters, &thread_current ()->elem);
+      list_insert_ordered(&sema->waiters, &thread_current ()->elem,
+                          priority_more, NULL);
       thread_block ();
     }
   sema->value--;
@@ -110,36 +107,25 @@ sema_try_down (struct semaphore *sema)
 
    This function may be called from an interrupt handler. */
 void
-sema_up (struct semaphore *sema)
+sema_up (struct semaphore *sema) 
 {
   enum intr_level old_level;
-  bool thread_unblocked = false; /* Flag to track if any thread was woken up. */
 
   ASSERT (sema != NULL);
 
   old_level = intr_disable ();
+
+  /* Wake up (unblock) the highest priority thread from the waiters list */
+  struct thread *t = NULL;
   if (!list_empty (&sema->waiters))
-  {
+    {
-    /* Enforces wake-up of the highest priority thread waiting for the
+      t = list_entry (list_pop_front (&sema->waiters), struct thread, elem);
-       semaphore. */
+      thread_unblock (t);
-    struct list_elem *e = list_max (&sema->waiters, priority_less, NULL);
+    }
-    list_remove (e);
+
-    thread_unblock (list_entry (e, struct thread, elem));
-    thread_unblocked = true;
-  }
   sema->value++;
   intr_set_level (old_level);
-
+  thread_yield ();
-  /* Yields the CPU in case the thread that has been woken up has a higher
-     priority that the current running thread, including the case when called
-     within an interrupt handler. */
-  if (thread_unblocked)
-  {
-    if (intr_context ())
-      intr_yield_on_return ();
-    else
-      thread_yield ();
-  }
 }
 
 static void sema_test_helper (void *sema_);
@@ -203,47 +189,6 @@ lock_init (struct lock *lock)
   sema_init (&lock->semaphore, 1);
 }
 
-/* Current thread donates its priority to donee, iteratively
-   propagating the donation in the case of chains in the wait-for graph.
-   Also keeps track of the donation by updating the donors list. Expects
-   interrupts to be disabled. */
-static void
-donate_priority (struct thread *donee) {
-  ASSERT (intr_get_level () == INTR_OFF);
-
-  struct thread *donor = thread_current ();
-  list_push_back (&donee->donors_list, &donor->donor_elem);
-  
-  while (donee != NULL)
-    {
-      /* Stop propagation of donation once a donee is reached that has
-         a higher effective priority (as its donees can't have less
-         priority than that being donated). */
-      if (donor->priority <= donee->priority)
-          break;
-
-      /* Also stop propagation of donation once a donee is reached with
-         no donees of its own (sink node in WFG). */
-      if (donee->waiting_lock == NULL)
-        {
-          /* Only the sink node of the WFG isn't waiting for a lock and
-             could be on the ready list. Thus, as its priority changed,
-             it must be reinserted into the list. */
-          enum intr_level old_level = intr_disable ();
-          donee->priority = donor->priority;
-          ready_list_reinsert (donee);
-          intr_set_level (old_level);
-          
-          donee = NULL;
-        }
-      else
-        {
-          donee->priority = donor->priority;
-          donee = donee->waiting_lock->holder;
-        }
-    }
-}
-
 /* Acquires LOCK, sleeping until it becomes available if
    necessary.  The lock must not already be held by the current
    thread.
@@ -259,19 +204,8 @@ lock_acquire (struct lock *lock)
   ASSERT (!intr_context ());
   ASSERT (!lock_held_by_current_thread (lock));
 
-  struct thread *t = thread_current ();
-
-  enum intr_level old_level = intr_disable ();
-  if (lock->holder != NULL)
-    {
-      t->waiting_lock = lock;
-      donate_priority (lock->holder);
-    }
-  intr_set_level (old_level);
-
   sema_down (&lock->semaphore);
   lock->holder = thread_current ();
-  t->waiting_lock = NULL;
 }
 
 /* Tries to acquires LOCK and returns true if successful or false
@@ -305,51 +239,6 @@ lock_release (struct lock *lock)
   ASSERT (lock != NULL);
   ASSERT (lock_held_by_current_thread (lock));
 
-  struct thread *current_thread = thread_current ();
-  struct thread *max_donor = NULL;
-
-  struct list orphan_list;
-  list_init (&orphan_list);
-
-  enum intr_level old_level = intr_disable ();
-  /* Loop through current thread's donors, removing the ones waiting for the
-     lock being released and keeping track of them (within orphan_list).
-     Also identifies the highest priority donor thread among them. */
-  struct list_elem *tail = list_tail (&current_thread->donors_list);
-  struct list_elem *e = list_begin (&current_thread->donors_list);
-  while (e != tail)
-    {
-      struct thread *donor = list_entry (e, struct thread, donor_elem);
-      struct list_elem *next = list_next (e);
-
-      /* Excludes donors that aren't waiting for the lock being released,
-         and tracks the rest. */
-      if (donor->waiting_lock == lock)
-        {
-          list_remove (e);
-          list_push_back (&orphan_list, e);
-
-          /* Identify highest priority donor. */
-          if (max_donor == NULL || donor->priority > max_donor->priority)
-            max_donor = donor;
-        }
-
-      e = next;
-    }
-
-  /* If there exists a maximum donor thread waiting for this lock to be
-     released, transfer the remaining orphaned donors to its donor list. */
-  if (max_donor != NULL)
-    {
-      while (!list_empty (&orphan_list))
-        list_push_back (&max_donor->donors_list, list_pop_front (&orphan_list));
-    }
-
-  intr_set_level (old_level);
-  /* Removal of donors to this thread may change its effective priority,
-     so recalculate. */
-  thread_recalculate_priority ();
-
   lock->holder = NULL;
   sema_up (&lock->semaphore);
 }
@@ -372,19 +261,6 @@ struct semaphore_elem
     struct semaphore semaphore;         /* This semaphore. */
   };
 
-/* Function that compares the two threads associated with the provided
-   pointers to their 'elem' member. Returns true if the thread associated
-   with a_ has a lower priority than that of b_. */
-static bool
-priority_less (const struct list_elem *a_, const struct list_elem *b_,
-               void *aux UNUSED)
-{
-  struct thread *a = list_entry (a_, struct thread, elem);
-  struct thread *b = list_entry (b_, struct thread, elem);
-
-  return a->priority < b->priority;
-}
-
 /* Function that compares the two *semaphores* associated with the provided
    list_elem structures. [i.e., takes list_elem of semaphore_elem, and]
    Returns true if the thread associated with the semaphore associated with a_
@@ -394,25 +270,43 @@ priority_less (const struct list_elem *a_, const struct list_elem *b_,
     priority of the first semaphore. This is useful when the thread has not been
     sema'd down yet. */
 static bool
-sema_priority_more(const struct list_elem *a, const struct list_elem *b,
+sema_priority_more(const struct list_elem *a_, const struct list_elem *b_,
-                   void *inserting_telem)
+                   void *aux)
 {
-  struct list_elem *te_a, *te_b;
+  int a_priority, b_priority;
-  
-  te_b = list_front (
-    &list_entry (b, struct semaphore_elem, elem)->semaphore.waiters);
 
-  if (inserting_telem == NULL)
+  /* If an aux is provided, then use it as the priority of the first semaphore.
-    {
+     Otherwise, get the priority of the first semaphore. */
-      te_a = list_front (
+  if (aux != NULL)
-        &list_entry (a, struct semaphore_elem, elem)->semaphore.waiters);
+    a_priority = *(int *) aux;
-    }
   else
     {
-      te_a = inserting_telem;
+      struct semaphore_elem *a = list_entry(a_, struct semaphore_elem, elem);
+
+      /* If waiters list is empty, return false (i.e., a has lower priority) */
+      if (list_empty(&a->semaphore.waiters))
+        return false;
+
+      /* Otherwise, get the thread with the highest priority from the waiters
+         list. By design, this is the first one in the list (See sema_down). */
+      struct thread *a_thread =
+        list_entry(list_front(&a->semaphore.waiters), struct thread, elem);
+
+      a_priority = a_thread->priority;
     }
 
-  return priority_more (te_a, te_b, NULL);
+  struct semaphore_elem *b = list_entry(b_, struct semaphore_elem, elem);
+
+  /* If waiters list is empty, return true (i.e., a has higher priority) */
+  if (list_empty(&b->semaphore.waiters))
+    return true;
+
+  struct thread *b_thread =
+    list_entry(list_front(&b->semaphore.waiters), struct thread, elem);
+
+  b_priority = b_thread->priority;
+
+  return a_priority > b_priority;
 }
 
 /* Initializes condition variable COND.  A condition variable
@@ -426,6 +320,38 @@ cond_init (struct condition *cond)
   list_init (&cond->waiters);
 }
 
+/* Returns true iff the priority of the only thread in the first singleton
+   semaphore is greater than the priority of the only thread in the second
+   singleton semaphore.
+   
+   Where this function is used for insertion in a singleton semaphore list, the
+   third argument may specify a list_elem * to assume corresponds to the thread
+   waiting for the inserting semaphore. For correctness, ensure this thread
+   calls sema_down () for this semaphore before future list accesses. */
+
+static bool
+singleton_sema_priority_greater (const struct list_elem *a, 
+                                 const struct list_elem *b,
+                                 void *insertingThread)
+{
+  struct list_elem *te_a, *te_b;
+  
+  te_b = list_front (
+    &list_entry (b, struct semaphore_elem, elem)->semaphore.waiters);
+
+  if (insertingThread == NULL)
+    {
+      te_a = list_front (
+        &list_entry (a, struct semaphore_elem, elem)->semaphore.waiters);
+    }
+  else
+    {
+      te_a = insertingThread;
+    }
+
+  return thread_priority_greater (te_a, te_b, NULL);
+}
+
 /* Atomically releases LOCK and waits for COND to be signaled by
    some other piece of code.  After COND is signaled, LOCK is
    reacquired before returning.  LOCK must be held before calling
@@ -457,7 +383,14 @@ cond_wait (struct condition *cond, struct lock *lock)
   ASSERT (lock_held_by_current_thread (lock));
   
   sema_init (&waiter.semaphore, 0);
-  list_push_back (&cond->waiters, &waiter.elem);
+
+  /* Insert the semaphore_elem into the waiters list in order of priority.
+     We pass the priority of the current thread as aux to sema_priority_more
+     because the thread has not been sema'd down yet (See sema_priority_more) */
+  int priority = thread_current ()->priority;
+  list_insert_ordered (&cond->waiters, &waiter.elem, sema_priority_more,
+                       &priority);
+
   lock_release (lock);
   sema_down (&waiter.semaphore);
   lock_acquire (lock);
@@ -478,14 +411,9 @@ cond_signal (struct condition *cond, struct lock *lock UNUSED)
   ASSERT (!intr_context ());
   ASSERT (lock_held_by_current_thread (lock));
 
-  if (!list_empty (&cond->waiters))
+  if (!list_empty (&cond->waiters)) 
-    {
+    sema_up (&list_entry (list_pop_front (&cond->waiters),
-      /* Enforce wake-up of highest priority thread within the singleton 
+                          struct semaphore_elem, elem)->semaphore);
-         semaphores waiting for condvar. */
-      struct list_elem *e = list_min (&cond->waiters, sema_priority_more, NULL);
-      list_remove (e);
-      sema_up (&list_entry (e, struct semaphore_elem, elem)->semaphore);
-    }
 }
 
 /* Wakes up all threads, if any, waiting on COND (protected by

src/threads/thread.c

@@ -4,8 +4,6 @@
 #include <random.h>
 #include <stdio.h>
 #include <string.h>
-#include "devices/timer.h"
-#include "threads/fixed-point.h"
 #include "threads/flags.h"
 #include "threads/interrupt.h"
 #include "threads/intr-stubs.h"
@@ -51,11 +49,9 @@ struct kernel_thread_frame
 static long long idle_ticks;    /* # of timer ticks spent idle. */
 static long long kernel_ticks;  /* # of timer ticks in kernel threads. */
 static long long user_ticks;    /* # of timer ticks in user programs. */
-static fp32_t load_avg = { 0 }; /* System load average. */
 
 /* Scheduling. */
 #define TIME_SLICE 4            /* # of timer ticks to give each thread. */
-#define PRI_UPDATE_FREQ 4       /* # of timer ticks to update priorities. */
 static unsigned thread_ticks;   /* # of timer ticks since last yield. */
 
 /* If false (default), use round-robin scheduler.
@@ -68,18 +64,12 @@ 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_thread (struct thread *, const char *name, int nice,
+static void init_thread (struct thread *, const char *name, int priority);
-                         int priority, fp32_t recent_cpu);
 static bool is_thread (struct thread *) UNUSED;
 static void *alloc_frame (struct thread *, size_t size);
-static int calculate_bsd_priority (fp32_t recent_cpu, int nice);
-static void update_recent_cpu (struct thread *t, void *aux UNUSED);
-static void recalculate_priority (struct thread *t);
 static void schedule (void);
 void thread_schedule_tail (struct thread *prev);
 static tid_t allocate_tid (void);
-static bool donor_priority_less (const struct list_elem *a_,
-                                 const struct list_elem *b_, void *aux UNUSED);
 
 /* Initializes the threading system by transforming the code
    that's currently running into a thread.  This can't work in
@@ -105,9 +95,7 @@ thread_init (void)
 
   /* Set up a thread structure for the running thread. */
   initial_thread = running_thread ();
-  fp32_t initial_thread_recent_cpu = { 0 };
+  init_thread (initial_thread, "main", PRI_DEFAULT);
-  init_thread (initial_thread, "main", NICE_DEFAULT, PRI_DEFAULT,
-               initial_thread_recent_cpu);
   initial_thread->status = THREAD_RUNNING;
   initial_thread->tid = allocate_tid ();
 }
@@ -157,35 +145,6 @@ thread_tick (void)
   else
     kernel_ticks++;
 
-  /* Update system load_avg and all threads recent_cpu every second. */
-  int64_t ticks = timer_ticks ();
-  if (thread_mlfqs)
-    {
-      if (t != idle_thread)
-          t->recent_cpu = fp_add_int (t->recent_cpu, 1);
-
-      if (ticks % TIMER_FREQ == 0)
-        {
-          size_t ready = threads_ready ();
-          if (t != idle_thread)
-            ready++;
-          fp32_t old_coeff = fp_div_int (fp_mul_int (load_avg, 59), 60);
-          fp32_t new_coeff = fp_div_int (fp_from_int (ready), 60);
-          load_avg = fp_add (old_coeff, new_coeff);
-
-          thread_foreach (update_recent_cpu, NULL);
-          /* Priorities have been updated, need to re-sort. */
-          list_sort (&ready_list, priority_more, NULL);
-        }
-
-      /* Recent cpu was updated, update priority. */
-      if (t != idle_thread && ticks % PRI_UPDATE_FREQ == 0)
-        {
-          t->base_priority = calculate_bsd_priority (t->recent_cpu, t->nice);
-          recalculate_priority (t);
-        }
-    }
-
   /* Enforce preemption. */
   if (++thread_ticks >= TIME_SLICE)
     intr_yield_on_return ();
@@ -233,8 +192,7 @@ thread_create (const char *name, int priority,
     return TID_ERROR;
 
   /* Initialize thread. */
-  struct thread *parent_thread = thread_current ();
+  init_thread (t, name, priority);
-  init_thread (t, name, parent_thread->nice, priority, parent_thread->recent_cpu);
   tid = t->tid = allocate_tid ();
 
   /* Prepare thread for first run by initializing its stack.
@@ -261,10 +219,10 @@ thread_create (const char *name, int priority,
 
   /* Add to run queue. */
   thread_unblock (t);
+  thread_yield ();
 
-  /* Yield if the newly created thread has higher priority than the current
+  /* Yield if the new thread has a higher priority than the current thread. */
-     thread. */
+  if (priority > thread_get_priority ())
-  if (t->priority > thread_get_priority ())
     thread_yield ();
 
   return tid;
@@ -305,7 +263,7 @@ thread_unblock (struct thread *t)
   ASSERT (t->status == THREAD_BLOCKED);
 
   /* Insert the thread back into the ready list in priority order. */
-  list_insert_ordered (&ready_list, &t->elem, priority_more, NULL);
+  list_insert_ordered(&ready_list, &t->elem, priority_more, NULL);
 
   t->status = THREAD_READY;
   intr_set_level (old_level);
@@ -377,11 +335,9 @@ thread_yield (void)
 
   old_level = intr_disable ();
 
-  if (cur != idle_thread)
+  /* Insert the thread back into the ready list in priority order. */
-    {
+  if (cur != idle_thread) 
-      /* Insert the thread back into the ready list in priority order. */
+    list_insert_ordered(&ready_list, &cur->elem, priority_more, NULL);
-      list_insert_ordered (&ready_list, &cur->elem, priority_more, NULL);
-    }
 
   cur->status = THREAD_READY;
   schedule ();
@@ -406,160 +362,66 @@ thread_foreach (thread_action_func *func, void *aux)
 }
 
 /* Function that compares the two threads associated with the provided
-   pointers to their 'elem' member. Returns true if the thread associated
+   list_elem structures. Returns true if the thread associated with a_ has
-   with a_ has a higher priority than that of b_. */
+   a higher priority than that of b_. */
 bool
 priority_more (const struct list_elem *a_, const struct list_elem *b_,
-               void *aux UNUSED)
+                   void *aux UNUSED)
 {
   struct thread *a = list_entry (a_, struct thread, elem);
   struct thread *b = list_entry (b_, struct thread, elem);
 
   return a->priority > b->priority;
-
 }
 
-/* Function that compares the two threads associated with the provided
+/* Sets the current thread's priority to NEW_PRIORITY. */
-   pointers to their 'donor_elem' member. Returns true if the thread associated
-   with a_ has a lower priority than that of b_. */
-static bool
-donor_priority_less (const struct list_elem *a_, const struct list_elem *b_,
-               void *aux UNUSED)
-{
-  struct thread *a = list_entry (a_, struct thread, donor_elem);
-  struct thread *b = list_entry (b_, struct thread, donor_elem);
-
-  return a->priority < b->priority;
-}
-
-/* Sets the current thread's base priority to new_base_priority.
-   Updates the current thread's effective priority if necessary. */
 void
-thread_set_priority (int new_base_priority)
+thread_set_priority (int new_priority) 
 {
+  ASSERT (PRI_MIN <= new_priority && new_priority <= PRI_MAX);
+  int old_priority = thread_get_priority ();
 
-  if (thread_mlfqs)
+  thread_current ()->priority = new_priority;
-    return;
+  if (new_priority < old_priority)
-
+    thread_yield ();
-  ASSERT (new_base_priority >= PRI_MIN);
-  ASSERT (new_base_priority <= PRI_MAX);
-
-  struct thread *t = thread_current ();
-
-  /* If the base priority is unchanged, do nothing. */
-  if (new_base_priority == t->base_priority)
-    return;
-
-  t->base_priority = new_base_priority;
-  recalculate_priority (t);
-
-  thread_yield ();
 }
 
-/* Returns the current thread's effective priority. */
+/* Returns the current thread's priority. */
 int
 thread_get_priority (void) 
 {
   return thread_current ()->priority;
 }
 
-
-/* Updates recent_cpu for a thread. */
-static void
-update_recent_cpu (struct thread *t, void *aux UNUSED)
-{
-  fp32_t curr_recent_cpu = t->recent_cpu;
-  fp32_t dbl_load_avg = fp_mul_int (load_avg, 2);
-  fp32_t recent_cpu_coeff
-      = fp_div (dbl_load_avg, fp_add_int (dbl_load_avg, 1));
-  t->recent_cpu
-      = fp_add_int (fp_mul (recent_cpu_coeff, curr_recent_cpu), t->nice);
-  // recent_cpu was updated, update priority.
-  t->base_priority = calculate_bsd_priority (t->recent_cpu, t->nice);
-  recalculate_priority (t);
-}
-
-/* Recalculates the effective priority of the current thread. */
-void
-thread_recalculate_priority (void)
-{
-  struct thread *t = thread_current ();
-  recalculate_priority (t);
-}
-
-static void
-recalculate_priority (struct thread *t)
-{
-  enum intr_level old_level = intr_disable ();
-  t->priority = t->base_priority;
-
-  /* If there are no donors to the current thread, then the effective
-     priority is just the base priority. */
-  if (!list_empty (&t->donors_list))
-    {
-      int max_donated_priority =
-        list_entry (list_max (&t->donors_list, donor_priority_less, NULL),
-                    struct thread, donor_elem)->priority;
-
-      /* The effective priority is the max donated priority if this is
-         higher than the base priority. */
-      if (max_donated_priority > t->priority)
-        t->priority = max_donated_priority;
-    }
-  intr_set_level (old_level);
-}
-
 /* Sets the current thread's nice value to NICE. */
 void
-thread_set_nice (int nice)
+thread_set_nice (int nice UNUSED) 
 {
-  ASSERT (NICE_MIN <= nice && nice <= NICE_MAX);
+  /* Not yet implemented. */
-
-  struct thread *t = thread_current ();
-  t->nice = nice;
-  t->base_priority = calculate_bsd_priority (t->recent_cpu, t->nice);
-  recalculate_priority (t);
-  struct thread *next_t
-      = list_entry (list_begin (&ready_list), struct thread, elem);
-  if (t->priority < next_t->priority)
-    thread_yield ();
 }
 
 /* Returns the current thread's nice value. */
 int
 thread_get_nice (void) 
 {
-  return thread_current ()->nice;
+  /* Not yet implemented. */
+  return 0;
 }
 
 /* Returns 100 times the system load average. */
 int
 thread_get_load_avg (void) 
 {
-  return fp_round (fp_mul_int (load_avg, 100));
+  /* Not yet implemented. */
+  return 0;
 }
 
 /* Returns 100 times the current thread's recent_cpu value. */
 int
 thread_get_recent_cpu (void) 
 {
-  return fp_round (fp_mul_int (thread_current ()->recent_cpu, 100));
+  /* Not yet implemented. */
-}
+  return 0;
-
-/* Reinsert thread t into the ready list at its correct position
-   in descending order of priority. Used when this thread's priority
-   may have changed. Must be called with interrupts disabled. */
-void
-ready_list_reinsert (struct thread *t)
-{
-  ASSERT (intr_get_level () == INTR_OFF);
-
-  /* If the thread isn't ready to run, do nothing. */
-  if (t->status != THREAD_READY)
-    return;
-
-  list_remove (&t->elem);
-  list_insert_ordered (&ready_list, &t->elem, priority_more, NULL);
 }
 
 /* Idle thread.  Executes when no other thread is ready to run.
@@ -635,8 +497,7 @@ is_thread (struct thread *t)
 /* Does basic initialization of T as a blocked thread named
    NAME. */
 static void
-init_thread (struct thread *t, const char *name, int nice, int priority,
+init_thread (struct thread *t, const char *name, int priority)
-             fp32_t recent_cpu)
 {
   enum intr_level old_level;
 
@@ -648,19 +509,9 @@ init_thread (struct thread *t, const char *name, int nice, int priority,
   t->status = THREAD_BLOCKED;
   strlcpy (t->name, name, sizeof t->name);
   t->stack = (uint8_t *) t + PGSIZE;
+  t->priority = priority;
   t->magic = THREAD_MAGIC;
 
-  t->base_priority
-      = thread_mlfqs ? calculate_bsd_priority (recent_cpu, nice) : priority;
-  list_init (&t->donors_list);
-  t->waiting_lock = NULL;
-
-  t->nice = nice;
-  t->recent_cpu = recent_cpu;
-  t->priority = t->base_priority;
-
-  t->exit_status = -1;
-
   old_level = intr_disable ();
   list_push_back (&all_list, &t->allelem);
   intr_set_level (old_level);
@@ -739,21 +590,6 @@ thread_schedule_tail (struct thread *prev)
     }
 }
 
-/* Calculates BSD priority for a thread */
-static int
-calculate_bsd_priority (fp32_t recent_cpu, int nice)
-{
-
-  ASSERT (thread_mlfqs);
-
-  int priority = PRI_MAX - (fp_round (recent_cpu) / 4) - (nice * 2);
-  if (priority < PRI_MIN)
-    return PRI_MIN;
-  if (priority > PRI_MAX)
-    return PRI_MAX;
-  return priority;
-}
-
 /* Schedules a new process.  At entry, interrupts must be off and
    the running process's state must have been changed from
    running to some other state.  This function finds another
@@ -791,6 +627,17 @@ allocate_tid (void)
   return tid;
 }
 
+/* Returns true iff the priority of the first list element's thread is greater
+   than that of the second list element's thread. */
+bool 
+thread_priority_greater (const struct list_elem *a, const struct list_elem *b,
+                         void *aux UNUSED)
+{
+  struct thread *ta = list_entry (a, struct thread, elem);
+  struct thread *tb = list_entry (b, struct thread, elem);
+  return ta->priority > tb->priority;
+}
+
 /* Offset of `stack' member within `struct thread'.
    Used by switch.S, which can't figure it out on its own. */
 uint32_t thread_stack_ofs = offsetof (struct thread, stack);

src/threads/thread.h

@@ -4,7 +4,6 @@
 #include <debug.h>
 #include <list.h>
 #include <stdint.h>
-#include "threads/fixed-point.h"
 
 /* States in a thread's life cycle. */
 enum thread_status
@@ -25,10 +24,6 @@ typedef int tid_t;
 #define PRI_DEFAULT 31                  /* Default priority. */
 #define PRI_MAX 63                      /* Highest priority. */
 
-#define NICE_MIN -20   /* Lowest niceness. */
-#define NICE_DEFAULT 0 /* Default niceness. */
-#define NICE_MAX 20    /* Highest niceness. */
-
 /* A kernel thread or user process.
 
    Each thread structure is stored in its own 4 kB page.  The
@@ -95,24 +90,9 @@ struct thread
     int priority;                       /* Priority. */
     struct list_elem allelem;           /* List element for all threads list. */
 
-    /* Donation Related */
-    int base_priority;                  /* Base priority of the thread. */
-    struct list donors_list;            /* List of threads that have donated
-                                           to this thread. */
-    struct lock *waiting_lock;          /* The lock that the current thread is
-                                           waiting for. */
-    struct list_elem donor_elem;        /* List element so that thread can be
-                                           enlisted in other donors list. */
-
-    /* MLFQS items */
-    int nice;                           /* Nice value for this thread */
-    fp32_t recent_cpu;                  /* Amount of time this process received */
-
     /* Shared between thread.c and synch.c. */
     struct list_elem elem;              /* List element. */
 
-    int exit_status;                    /* Exit Status: 0 = successful exit. */
-
 #ifdef USERPROG
     /* Owned by userprog/process.c. */
     uint32_t *pagedir;                  /* Page directory. */
@@ -155,13 +135,13 @@ bool priority_more (const struct list_elem *a_, const struct list_elem *b_,
                     void *aux UNUSED);
 int thread_get_priority (void);
 void thread_set_priority (int);
-void thread_recalculate_priority (void);
 
 int thread_get_nice (void);
 void thread_set_nice (int);
 int thread_get_recent_cpu (void);
 int thread_get_load_avg (void);
 
-void ready_list_reinsert (struct thread *t);
+/* Returns true iff the priority of the first list element's thread is greater
-
+   than that of the second list element's thread. */
+list_less_func thread_priority_greater;
 #endif /* threads/thread.h */

src/userprog/process.c

@@ -14,127 +14,57 @@
 #include "threads/flags.h"
 #include "threads/init.h"
 #include "threads/interrupt.h"
-#include "threads/synch.h"
 #include "threads/palloc.h"
-#include "threads/malloc.h"
 #include "threads/thread.h"
 #include "threads/vaddr.h"
-#include "threads/synch.h"
-#include "devices/timer.h"
-
-/* Defines the native number of bytes processed by the processor
-   (for the purposes of alignment). */
-#define WORD_SIZE 4
-
-/* Keeps track of the position of pointers to user program arguments
-   within a linked list. */
-struct arg_elem
-  {
-    char* arg;
-    struct list_elem elem;
-  };
-
-/* Holds the data required to be passed from a kernel thread to a thread
-   that executes process_start for the purpose of starting a user process. */
-struct process_start_data
-  {
-    char *cmd; /* Pointer to a copy of the command used to execute the process.
-                  Allocated a page that must be freed by process_start. */
-    char *cmd_saveptr; /* Value pointed to by 'saveptr' argument used by
-                          successive calls to strtok_r to split 'cmd' into
-                          tokens while maintaining state. */
-    char file_name[FNAME_MAX_LEN + 1]; /* Name of the file of the process to
-                                      be started. */
-  };
 
 static thread_func start_process NO_RETURN;
 static bool load (const char *cmdline, void (**eip) (void), void **esp);
 
-/* Starts a new thread running a user program executed via
+/* Starts a new thread running a user program loaded from
-   CMD.  The new thread may be scheduled (and may even exit)
+   FILENAME.  The new thread may be scheduled (and may even exit)
    before process_execute() returns.  Returns the new process's
    thread id, or TID_ERROR if the thread cannot be created. */
 tid_t
-process_execute (const char *cmd) 
+process_execute (const char *file_name) 
 {
-  char *cmd_copy;
+  char *fn_copy;
   tid_t tid;
-  
-  struct process_start_data *data = malloc (sizeof (struct process_start_data));
-  if (data == NULL)
-    {
-      return TID_ERROR;
-    }
 
-  /* Make a copy of command.
+  /* Make a copy of FILE_NAME.
      Otherwise there's a race between the caller and load(). */
-  cmd_copy = palloc_get_page (0);
+  fn_copy = palloc_get_page (0);
-  if (cmd_copy == NULL)
+  if (fn_copy == NULL)
     return TID_ERROR;
+  strlcpy (fn_copy, file_name, PGSIZE);
 
-  /* Imposing implicit limit that the command line arguments
+  /* Create a new thread to execute FILE_NAME. */
-    including the user program name fit within a single page. */
+  tid = thread_create (file_name, PRI_DEFAULT, start_process, fn_copy);
-  strlcpy (cmd_copy, cmd, PGSIZE);
-
-  /* Retrieve first argument of command, which is the file name
-     of the process. */
-  char *file_name = strtok_r (cmd_copy, " ", &data->cmd_saveptr);
-
-  /* Create a new thread to execute the command, by initializing
-     it running the function 'start_process' with the appropriate
-     arguments. For details of arguments, see 'start_process'. */
-  data->cmd = cmd_copy;
-  strlcpy (data->file_name, file_name, FNAME_MAX_LEN + 1);
-
-  tid = thread_create (file_name, PRI_DEFAULT, start_process, data);
   if (tid == TID_ERROR)
-    palloc_free_page (cmd_copy); 
+    palloc_free_page (fn_copy); 
   return tid;
 }
 
-static bool install_page (void *upage, void *kpage, bool writable);
+/* A thread function that loads a user process and starts it
-static bool process_init_stack (char *cmd_saveptr, void **esp, char *file_name);
+   running. */
-static void *push_to_stack (void **esp, void *data, size_t data_size);
-#define push_var_to_stack(esp, var) (push_to_stack (esp, &var, sizeof (var)))
-
-/* Make the current thread execute 'cmd', passing in a copy of the
-   command string used for processing, the saveptr used by strtok_r
-   (in order to further tokenize the same command and retrieve its
-   arguments), as well as the name of the file being executed. This
-   involves loading the specified file and starting it running. */
 static void
-start_process (void *proc_start_data)
+start_process (void *file_name_)
 {
+  char *file_name = file_name_;
   struct intr_frame if_;
   bool success;
 
-  struct process_start_data *data = proc_start_data;
-
   /* Initialize interrupt frame and load executable. */
   memset (&if_, 0, sizeof if_);
   if_.gs = if_.fs = if_.es = if_.ds = if_.ss = SEL_UDSEG;
   if_.cs = SEL_UCSEG;
   if_.eflags = FLAG_IF | FLAG_MBS;
-  success = load (data->file_name, &if_.eip, &if_.esp);
+  success = load (file_name, &if_.eip, &if_.esp);
 
   /* If load failed, quit. */
+  palloc_free_page (file_name);
   if (!success) 
-    {
+    thread_exit ();
-      palloc_free_page (data->cmd);
-      goto fail;
-    }
-
-  /* Initialize user process stack and free page used to store the
-     command that executed the process. */
-  success = process_init_stack (data->cmd_saveptr, &if_.esp, data->file_name);
-  palloc_free_page (data->cmd);
-  
-  /* If stack initialization failed, free resources and quit. */
-  if (!success)
-    {
-      process_exit ();
-      goto fail;
-    }
 
   /* Start the user process by simulating a return from an
      interrupt, implemented by intr_exit (in
@@ -144,109 +74,6 @@ start_process (void *proc_start_data)
      and jump to it. */
   asm volatile ("movl %0, %%esp; jmp intr_exit" : : "g" (&if_) : "memory");
   NOT_REACHED ();
-
-/* If starting the process failed, free its common resources and exit. */
- fail:
-  free (data);
-  thread_exit ();
-}
-
-/* Helper function that initializes the stack of a newly created 
-   user process. Returns true if successful, false otherwise. */
-static bool
-process_init_stack (char *cmd_saveptr, void **esp, char *file_name)
-  {
-    /* Load command line argument *data* to user process stack.
-       This can't cause overflow due to enforcing that the size of
-       command line input must fit in a page. Also keep track
-       of pointers to the argument data within a linked list. */
-    struct list arg_list;
-    list_init (&arg_list);
-
-    char *arg = file_name;
-    int arg_count = 0;
-    while (arg != NULL)
-      {
-        push_to_stack (esp, arg, (strlen (arg) + 1) * sizeof (char));
-        
-        struct arg_elem *arg_elem = malloc (sizeof (struct arg_elem));
-        if (arg_elem == NULL)
-          {
-            printf("ERROR: Couldn't allocate argument pointer memory for %s!\n",
-                   thread_current ()->name);
-            return false;
-          }
-
-        arg_elem->arg = *esp;
-        list_push_front (&arg_list, &arg_elem->elem);
-
-        arg_count++;
-        arg = strtok_r (NULL, " ", &cmd_saveptr);
-      }
-
-    /* Calculate the remaining number of bytes that need to be written
-       to the user process stack in order to check for possible overflow. */
-    size_t align_size = ((unsigned int) *esp % WORD_SIZE) * sizeof (uint8_t);
-    size_t argv_data_size = (arg_count + 1) * sizeof (char *);
-    size_t argv_size = sizeof (char **);
-    size_t argc_size = sizeof (int);
-    size_t return_addr_size = sizeof (void *);
-    size_t remaining_size = align_size + argv_data_size + argv_size + argc_size
-                            + return_addr_size;
-
-    /* If pushing the rest of the data required for the stack would cause
-       overflow, allocate an extra page that is contiguous within the
-       virtual address space (below the current address range). */ 
-    if (PHYS_BASE - *esp + remaining_size > PGSIZE)
-      {
-        uint8_t *kpage = palloc_get_page (PAL_USER | PAL_ZERO);
-        if (!install_page (((uint8_t *) PHYS_BASE) - PGSIZE * 2, kpage, true))
-          return false;
-      }
-
-    /* Align stack pointer to word size before pushing argv elements for
-       performance. */
-    *esp -= align_size;
-    
-    /* Push a null pointer sentinel inside argv. */
-    char *null_sentinel = NULL;
-    push_var_to_stack (esp, null_sentinel); 
-
-    /* Push pointers to process arguments from argument linked list */
-    struct list_elem *e = list_begin (&arg_list);
-    struct list_elem *tail = list_tail (&arg_list);
-    while (e != tail)
-      {
-        struct arg_elem *arg_elem = list_entry (e, struct arg_elem, elem);
-        
-        push_var_to_stack(esp, arg_elem->arg);
-        
-        e = list_next (e);
-        free (arg_elem);
-      }
-
-    /* Push pointer to the start of argv array. */
-    char **argv = *esp;
-    push_var_to_stack(esp, argv);
-
-    /* Push the number of arguments to the stack. */
-    push_var_to_stack(esp, arg_count);
-
-    /* Push fake return address (null pointer). */
-    push_var_to_stack (esp, null_sentinel); 
-
-    return true;
- }
-
-/* Helper function that pushes the first 'data_size' bytes stored
-   in the address '*data' into the stack given a pointer to the
-   stack pointer '**esp'. */
-static void *
-push_to_stack (void **esp, void *data, size_t data_size)
-{
-  *esp -= data_size;
-  memcpy (*esp, data, data_size);
-  return *esp;
 }
 
 /* Waits for thread TID to die and returns its exit status. 
@@ -261,12 +88,7 @@ push_to_stack (void **esp, void *data, size_t data_size)
 int
 process_wait (tid_t child_tid UNUSED) 
 {
-  /* As a temporary wait, waiting will just put the thread to sleep for one
+  return -1;
-     second (TIMER_FREQ = 100 ticks ~ 1 second). */
-  /* TODO: Implement process_wait () correctly. Remove the next line. */
-  timer_sleep (TIMER_FREQ);
-
-  return 0; /* TODO: Change this too */
 }
 
 /* Free the current process's resources. */
@@ -276,8 +98,6 @@ process_exit (void)
   struct thread *cur = thread_current ();
   uint32_t *pd;
 
-  printf ("%s: exit(%d)\n", cur->name, cur->exit_status);
-
   /* Destroy the current process's page directory and switch back
      to the kernel-only page directory. */
   pd = cur->pagedir;
@@ -498,6 +318,8 @@ load (const char *file_name, void (**eip) (void), void **esp)
 
 /* load() helpers. */
 
+static bool install_page (void *upage, void *kpage, bool writable);
+
 /* Checks whether PHDR describes a valid, loadable segment in
    FILE and returns true if so, false otherwise. */
 static bool

src/userprog/syscall.c

@@ -1,68 +1,11 @@
 #include "userprog/syscall.h"
-#include "devices/shutdown.h"
-#include "devices/input.h"
-#include "threads/vaddr.h"
-#include "threads/interrupt.h"
-#include "threads/thread.h"
-#include "userprog/process.h"
 #include <stdio.h>
 #include <syscall-nr.h>
+#include "threads/interrupt.h"
+#include "threads/thread.h"
 
 static void syscall_handler (struct intr_frame *);
 
-/* A syscall_function is a function that receives up to 3 arguments, the
-   arguments to the functions are either ints or pointers taking up to 32 bits
-   in size. */
-typedef uintptr_t (*syscall_function) (uintptr_t, uintptr_t, uintptr_t);
-
-/* System call function prototypes */
-static void syscall_halt (void);
-static void syscall_exit (int status);
-static pid_t syscall_exec (const char *cmd_line);
-static int syscall_wait (pid_t pid);
-static bool syscall_create (const char *file, unsigned initial_size);
-static bool syscall_remove (const char *file);
-static int syscall_open (const char *file);
-static int syscall_filesize (int fd);
-static int syscall_read (int fd, void *buffer, unsigned size);
-static int syscall_write (int fd, const void *buffer, unsigned size);
-static void syscall_seek (int fd, unsigned position);
-static unsigned syscall_tell (int fd);
-static void syscall_close (int fd);
-
-static void *validate_user_pointer (const void *ptr, size_t size);
-
-/* A struct defining a syscall_function pointer along with its arity. */
-typedef struct
-  {
-    syscall_function function;    /* Function pointer. */
-    int arity;                    /* Number of arguments of the function. */
-  } syscall_arguments;
-
-/* A look-up table mapping numbers to system call functions with their number of
-   arguments. */
-static const syscall_arguments syscall_lookup[] =
-{
-  [SYS_HALT] = {(syscall_function) syscall_halt, 0},
-  [SYS_EXIT] = {(syscall_function) syscall_exit, 1},
-  [SYS_EXEC] = {(syscall_function) syscall_exec, 1},
-  [SYS_WAIT] = {(syscall_function) syscall_wait, 1},
-  [SYS_CREATE] = {(syscall_function) syscall_create, 2},
-  [SYS_REMOVE] = {(syscall_function) syscall_remove, 1},
-  [SYS_OPEN] = {(syscall_function) syscall_open, 1},
-  [SYS_FILESIZE] = {(syscall_function) syscall_filesize, 1},
-  [SYS_READ] = {(syscall_function) syscall_read, 3},
-  [SYS_WRITE] = {(syscall_function) syscall_write, 3},
-  [SYS_SEEK] = {(syscall_function) syscall_seek, 2},
-  [SYS_TELL] = {(syscall_function) syscall_tell, 1},
-  [SYS_CLOSE] = {(syscall_function) syscall_close, 1},
-};
-
-/* The number of syscall functions (i.e, number of elements) within the
-   syscall_lookup table. */
-static const int LOOKUP_SIZE
-  = sizeof (syscall_lookup) / sizeof (syscall_arguments);
-
 void
 syscall_init (void) 
 {
@@ -70,165 +13,8 @@ syscall_init (void)
 }
 
 static void
-syscall_handler (struct intr_frame *f)
+syscall_handler (struct intr_frame *f UNUSED) 
 {
-  /* First, read the system call number from the stack. */
+  printf ("system call!\n");
-  validate_user_pointer (f->esp, 1);
-  unsigned syscall_number = *(int *) f->esp;
-
-  /* Ensures the number corresponds to a system call that can be handled. */
-  if (syscall_number >= LOOKUP_SIZE)
-    thread_exit ();
-
-  syscall_arguments syscall = syscall_lookup[syscall_number];
-
-  /* Next, read and copy the arguments from the stack pointer. */
-  validate_user_pointer (f->esp + sizeof (uintptr_t),
-                         syscall.arity * sizeof (uintptr_t));
-  uintptr_t args[3] = {0};
-  for (int i=0; i < syscall.arity; i++)
-      args[i] = *(uintptr_t *) (f->esp + sizeof (uintptr_t) * (i + 1));
-
-  /* Call the function that handles this system call with the arguments. When
-     there is a return value it is stored in f->eax. */
-  f->eax = syscall.function (args[0], args[1], args[2]);
-}
-
-static void
-syscall_halt (void)
-{
-  shutdown_power_off ();
-}
-
-static void
-syscall_exit (int status)
-{
-  /* Sets exit_status of the thread to status. thread_exit () will call
-     process_exit () if user programs are allowed. */
-  thread_current ()->exit_status = status;
   thread_exit ();
 }
-
-static pid_t
-syscall_exec (const char *cmd_line UNUSED)
-{
-  //TODO
-  return 0;
-}
-
-static int
-syscall_wait (pid_t pid)
-{
-  return process_wait (pid);
-}
-
-static bool
-syscall_create (const char *file UNUSED, unsigned initial_size UNUSED)
-{
-  //TODO
-  return 0;
-}
-
-static bool
-syscall_remove (const char *file UNUSED)
-{
-  //TODO
-  return 0;
-}
-
-static int
-syscall_open (const char *file UNUSED)
-{
-  //TODO
-  return 0;
-}
-
-static int
-syscall_filesize (int fd UNUSED)
-{
-  //TODO
-  return 0;
-}
-
-static int
-syscall_read (int fd, void *buffer, unsigned size)
-{
-  /* Only console (fd = 0) or other files, not including STDOUT, (fd > 1) are
-     allowed. */
-  if (fd < 0 && fd != STDOUT_FILENO)
-    return -1;
-
-  validate_user_pointer (buffer, size);
-
-  if (fd == STDIN_FILENO)
-    {
-      /* Reading from the console. */
-      char *write_buffer = buffer;
-      for (int i = 0; i < size; i++)
-        write_buffer[i] = input_getc ();
-
-      return size;
-    }
-  else
-    {
-      /* Reading from a file. */
-      return 0; // TODO: Implement Write to Files
-    }
-}
-
-static int
-syscall_write (int fd, const void *buffer, unsigned size)
-{
-  /* Only console (fd = 1) or other files, not including STDIN, (fd > 1) are
-     allowed. */
-  if (fd <= 0)
-    return 0;
-
-  validate_user_pointer (buffer, size);
-
-  if (fd == STDOUT_FILENO)
-    {
-      /* Writing to the console. */
-      putbuf (buffer, size);
-      return size;
-    }
-  else
-    {
-      /* Writing to a file. */
-      return 0; // TODO: Implement Write to Files
-    }
-}
-
-static void
-syscall_seek (int fd UNUSED, unsigned position UNUSED)
-{
-  //TODO
-}
-
-static unsigned
-syscall_tell (int fd UNUSED)
-{
-  //TODO
-  return 0;
-}
-
-static void
-syscall_close (int fd UNUSED)
-{
-  //TODO
-}
-
-/* Validates if a block of memory starting at PTR and of size SIZE bytes is
-   fully contained within user virtual memory. Kills the thread (by calling
-   thread_exit) if the memory is invalid. Otherwise, returns the PTR given.
-   If the size is 0, the function does no checks and returns PTR.*/
-static void *
-validate_user_pointer (const void *ptr, size_t size)
-{
-  if (size > 0 && (ptr == NULL ||
-                   !is_user_vaddr (ptr) ||
-                   !is_user_vaddr (ptr + size - 1)))
-    thread_exit ();
-
-  return ptr;
-}

src/userprog/syscall.h

@@ -1,8 +1,6 @@
 #ifndef USERPROG_SYSCALL_H
 #define USERPROG_SYSCALL_H
 
-typedef int pid_t;
-
 void syscall_init (void);
 
 #endif /* userprog/syscall.h */