Make exit more scalable

b3ad63d6 · Frans Kaashoek · 9fee0d5f · b3ad63d6
--- a/proc.c
+++ b/proc.c
@@ -16,8 +16,6 @@ int nextpid = 1;
 extern void forkret(void);
 extern void trapret(void);

-// static void wakeup1(struct ptable *pt, void *chan);
-
 void
 pinit(void)
 {
@@ -31,7 +29,7 @@ pinit(void)

    for (i = 0; i < NPROC; i++) {
      initlock(&ptables[c].proc[i].lock, ptables[c].proc[i].name);
-      initlock(&ptables[c].proc[i].cv.lock, ptables[c].proc[i].name);
+      initlock(&ptables[c].proc[i].cv.lock, ptables[c].proc[i].name); // XXX cv_init
    }

    runqs[c].name[0] = (char) (c + '0');
@@ -99,7 +97,7 @@ addrun1(struct runq *rq, struct proc *p)
      return;
    }
  }
-  p->state = RUNNABLE;   // race?
+  p->state = RUNNABLE;   // XXX race?
  SLIST_INSERT_HEAD(&rq->runq, p, run_next);
 }

@@ -229,9 +227,8 @@ fork(void)
 void
 exit(void)
 {
-  struct proc *p;
+  struct proc *p, *np;
  int fd;
-  int c;
  int wakeupinit;

  if(proc == initproc)
@@ -252,16 +249,14 @@ exit(void)

  // Pass abandoned children to init.
  wakeupinit = 0;
-  for (c = 0; c < NCPU; c++) {
-    acquire(&ptables[c].lock);  // XXX Unscalable
-    for(p = ptables[c].proc; p < &ptables[c].proc[NPROC]; p++){
-      if(p->parent == proc){
-	p->parent = initproc;
-	if(p->state == ZOMBIE)
+  SLIST_FOREACH_SAFE(p, &proc->childq, child_next, np) {
+    acquire(&p->lock);
+    p->parent = initproc;
+    if(p->state == ZOMBIE)
 	  wakeupinit = 1;
-      }
-    }
-    release(&ptables[c].lock); 
+    SLIST_REMOVE(&proc->childq, p, proc, child_next);
+    SLIST_INSERT_HEAD(&initproc->childq, p, child_next);  // XXX lock?
+    release(&p->lock);
  }

  // Parent might be sleeping in wait().
@@ -291,7 +286,7 @@ wait(void)
  cprintf("wait %d\n", proc->pid);

  for(;;){
-    // Scan through table looking for zombie children.
+    // Scan children for ZOMBIEs
    havekids = 0;
    acquire(&proc->lock);
    SLIST_FOREACH_SAFE(p, &proc->childq, child_next, np) {