P3 Patches

patch #1: fixing adding in kundeschedule

commit 41a7fcc7399f718f3121ab34649191d7385c1a1d
Author: Amanda M. Watson <[email protected]>
Date:   Mon Apr 14 19:57:47 2014 -0400

    added back in kundeschedule

diff --git a/kern/drivers/keyboard.c b/kern/drivers/keyboard.c
index 6862f81..3886241 100644
--- a/kern/drivers/keyboard.c
+++ b/kern/drivers/keyboard.c
@@ -85,7 +85,7 @@ void keyboard_handler() {
 
     if (c == '\n') {
       rl.active->state = RUNNING;
-      schedule(rl.active, FRONT);
+      kundeschedule(rl.active);
       context_switch_needed = 1;
     }
   }
diff --git a/kern/inc/schedule.h b/kern/inc/schedule.h
index 1cb2260..711f828 100644
--- a/kern/inc/schedule.h
+++ b/kern/inc/schedule.h
@@ -68,6 +68,6 @@ void insert_sleep_queue(TCB_t *thread, int ticks);
 void wakeup_sleep_queue(int ticks);
 void run_thread(TCB_t *thread);
 void validate_esp();
-
+void kundeschedule (TCB_t *thread);
 #endif /* _SCHEDULE_H */
 
diff --git a/kern/locks/kcond.c b/kern/locks/kcond.c
index 3a9b998..b0565bf 100644
--- a/kern/locks/kcond.c
+++ b/kern/locks/kcond.c
@@ -6,7 +6,7 @@
  * @bug None known.
  *
  * Our kcondvars function largely in the same manner as our P2 condvars, with
- * the exception that we have finer grained scheduler control and so can more
+ * the exception that we have finer grained kundescheduler control and so can more
  * accurately handle sleeping/waking up of threads.
  *
  * We have no use at present for _broadcast, so it has not been ported.  One
@@ -151,7 +151,7 @@ void kcond_signal(kcond *kv) {
       wakeup->tcb->cond_ref = NULL;
       wakeup->tcb->state = READY;
       LPRINTF("signaling %d", wakeup->tcb->tid);
-      schedule(wakeup->tcb, FRONT);
+      kundeschedule(wakeup->tcb);
     )
   }
 
diff --git a/kern/locks/kmut.c b/kern/locks/kmut.c
index 37a59c1..c34701e 100644
--- a/kern/locks/kmut.c
+++ b/kern/locks/kmut.c
@@ -158,8 +158,8 @@ void kmut_unlock(kmut *km) {
   
   if (run_this != NULL) {
     LPRINTF("LOCK: waking up %d in %p", run_this->tcb->tid, km);
-    /* scheduler is protected here */
-    schedule(run_this->tcb, FRONT);
+    /* kundescheduler is protected here */
+    kundeschedule(run_this->tcb);
   }
 
   km->lock_avail = 1; /* kxchg not currently needed here */
diff --git a/kern/schedule/schedule.c b/kern/schedule/schedule.c
index b4e3712..03ca0bb 100644
--- a/kern/schedule/schedule.c
+++ b/kern/schedule/schedule.c
@@ -154,6 +154,21 @@ void insert_sleep_queue(TCB_t *thread, int ticks) {
     return;
 }
 
+void kundeschedule (TCB_t *thread) {
+    assert(thread != NULL);
+    assert(thread != proc_master.scheduler.running);
+
+    Q_REMOVE(&(proc_master.scheduler.desc_queue), thread, desc_queue_link);
+
+    LPRINTF("LOCK SCHEDULE: undescheduled %d from desc queue (now length %d)", 
+            thread->tid,
+            proc_master.scheduler.desc_queue.count);
+
+    schedule(thread, FRONT);
+    validate_esp();
+
+}
+
 /* @brief given a running/runnable thread, insert it into the deschedule queue
  * to be woken up at another time.
  *

patch #2: fixing correctness issue in wait()

commit 0d13b81fe6f762594b8edb96b0d90fc1b9b116b1
Author: Amanda M. Watson <[email protected]>
Date:   Mon Apr 14 20:18:19 2014 -0400

    wait now checks to see if there are too many threads already waiting

diff --git a/kern/inc/pcb.h b/kern/inc/pcb.h
index dcddbe6..92fa960 100644
--- a/kern/inc/pcb.h
+++ b/kern/inc/pcb.h
@@ -54,6 +54,7 @@ typedef struct pcb_node {
     Q_NEW_LINK(pcb_node) child_queue_link;
     
     int child_ref; // how many children are still active (even re-parented) 
+    int wait_count; // how many peer threads are currently descheduled in wait
     exit_status_queue child_exits; // holds exit statuses of exited children
     kcond proc_cond; // used for sleep when proc calls wait
     // the process' exit status, to be collected when the proc vanishes and 
diff --git a/kern/proc/fork.c b/kern/proc/fork.c
index cbce9b6..43790b9 100644
--- a/kern/proc/fork.c
+++ b/kern/proc/fork.c
@@ -291,8 +291,10 @@ int wait(void *status_ptr) {
         LPRINTF("%d returning dead exit status", thread->tid);
         return tid;
     } 
-    // if there are still live children, deschedule until one exits 
-    if (proc->child_ref) {
+    // if there are still live children and no peer threads are already waiting
+    // on them
+    if (proc->child_ref && proc->wait_count < proc->child_ref) {
+        proc->wait_count++;
         kcond_wait(&(proc->proc_cond), &(proc->proc_lock));
         LPRINTF("%d waking up from cond_wait", thread->tid);
         // we come back holding the lock, and should now have an exit
@@ -300,6 +302,7 @@ int wait(void *status_ptr) {
         exit_status = Q_GET_FRONT(&(proc->child_exits));
         assert(exit_status != NULL);
         Q_REMOVE(&(proc->child_exits), exit_status, exit_status_link);
+        proc->wait_count--;
         kmut_unlock(&(proc->proc_lock));
         /* if wait fails, it's because I'm bad at pointers */
         if (copy_to_user(status_ptr, &(exit_status->exit_status), 
diff --git a/kern/structures/pcb.c b/kern/structures/pcb.c
index ce7aadf..1cec851 100644
--- a/kern/structures/pcb.c
+++ b/kern/structures/pcb.c
@@ -56,6 +56,7 @@ int PCB_init(PCB_t *proc) {
     /* init status info: process is initially alive with 
      * exit status 0 (as per fork spec) and no parent */
     proc->state = P_ALIVE;
+    proc->wait_count = 0;
     proc->parent = NULL;
     proc->child_ref = 0;
     proc->thread_count = 0;

Patch #3: fixing cr2 race

commit caf89664c4fef21052373925de6ebc893bc4ec77
Author: Amanda M. Watson <[email protected]>
Date:   Mon Apr 14 20:11:18 2014 -0400

    fixed cr2 race

diff --git a/kern/interrupts/page_fault_handler.c b/kern/interrupts/page_fault_handler.c
index f5e7ef3..5c773bd 100644
--- a/kern/interrupts/page_fault_handler.c
+++ b/kern/interrupts/page_fault_handler.c
@@ -51,6 +51,10 @@ int page_fault_handler(ureg_t *ureg) {
                     GET_FLAGS(phys_addr) | READ_WRITE_BIT) >= 0);
         kmut_unlock(&(PD->PD_lock));
         return 0;
+        /* in the case that the memory allocation has already been resolved, 
+         * simply return without setting the page */
+    } else if ((void *)GET_ALIGNED_ADDR(phys_addr) != NULL) {
+        return 0;
     }
     /* we don't take page faults in the kernel! That'd be absurd! */
     assert (ureg->ss == SEGSEL_USER_DS);