Explain why a null pointer sentinel must be pushed on the stack.

[pintos-anon] / ta-advice / HW3

diff --git a/ta-advice/HW3 b/ta-advice/HW3
index 6143c24bd7674465746be26aadadb19a9d7ad4f5..c0860c8e8d8211d57cc8d72a996647de094d14f7 100644 (file)
--- a/ta-advice/HW3
+++ b/ta-advice/HW3
@@ -61,8 +61,9 @@ A1:
 
 A2:
 
 
 A2:
 

-    The answer should describe code, not data; the data structures
-    have already been explained in A1.
+    The answer generally boils down to traversing the data structure
+    from A1.  The answer should describe code, not data; the data
+    structures have already been explained in A1.

 
 A3:
 
 
 A3:
 


@@ -113,8 +114,6 @@ A5:
     easier to find all the pages that belong to a given process (for
     cleanup when a process dies).
 
     easier to find all the pages that belong to a given process (for
     cleanup when a process dies).
 

-Check the submitted code, by hand, for the following: 
-

                       PAGING TO AND FROM DISK
                       =======================
 
                       PAGING TO AND FROM DISK
                       =======================
 


@@ -255,14 +254,16 @@ B8:
     Several possible answers:
 
        - Pre-lock all the pages that the system call will access,
     Several possible answers:
 
        - Pre-lock all the pages that the system call will access,

-          then unlock them when the system call completes.
+          then unlock them when the system call completes.  There must
+          be a discussion of how to avoid deadlock among processes
+          that, among them have all of the user pool locked, and want
+          more.

 
        - Page fault in kernel.
 
 
        - Page fault in kernel.
 

-       - Acquire a global lock needed to evict pages.  (But there
-          should be some additional explanation of how the system call
-          makes sure that those pages are in main memory in the first
-          place.)
+       - Acquire a global lock needed to evict pages.  There should
+          be some additional explanation of how the system call makes
+          sure that those pages are in main memory in the first place.

 
 B9:
 
 
 B9:
 


@@ -270,9 +271,8 @@ B9:
     to claim that the conditions for deadlock are "rare" or that the
     window in which deadlock can occur is "short" are not acceptable.
     In a proper design, deadlock is impossible, not just rare.  Deduct
     to claim that the conditions for deadlock are "rare" or that the
     window in which deadlock can occur is "short" are not acceptable.
     In a proper design, deadlock is impossible, not just rare.  Deduct

-    points.
-
-Check the submitted code, by hand, for the following:
+    points.  (This deduction is listed under B5 because similar claims
+    are common there.)

 
                         MEMORY MAPPED FILES
                         ===================
 
                         MEMORY MAPPED FILES
                         ===================


@@ -293,7 +293,7 @@ C2:
     For some reason, students sometimes talk about permanently
     assigning or pre-reserving memory mapped files to swap slots or to
     frames in physical memory here.  That's incorrect.  The assignment
     For some reason, students sometimes talk about permanently
     assigning or pre-reserving memory mapped files to swap slots or to
     frames in physical memory here.  That's incorrect.  The assignment

-    is explicit that mapping should be lazily loaded and written back
+    is explicit that mappings should be lazily loaded and written back

     to their files, not to swap.
 
 C3:
     to their files, not to swap.
 
 C3: