possible fixes

db4ad0cd · Nickolai Zeldovich · be63c0b8 · db4ad0cd
--- a/proc.c
+++ b/proc.c
@@ -239,11 +239,14 @@ fork(int flags)
      np->ofile[i] = filedup(proc->ofile[i]);
  np->cwd = idup(proc->cwd);

-  SLIST_INSERT_HEAD(&proc->childq, np, child_next);  // XXX lock?
  pid = np->pid;
  addrun(np);
  safestrcpy(np->name, proc->name, sizeof(proc->name));

+  acquire(&proc->lock);
+  SLIST_INSERT_HEAD(&proc->childq, np, child_next);
+  release(&proc->lock);
+
  return pid;
 }

@@ -279,18 +282,21 @@ exit(void)
    if(p->state == ZOMBIE)
      wakeupinit = 1;
    SLIST_REMOVE(&proc->childq, p, proc, child_next);
-    SLIST_INSERT_HEAD(&initproc->childq, p, child_next);  // XXX lock?
    release(&p->lock);
+
+    acquire(&initproc->lock);
+    SLIST_INSERT_HEAD(&initproc->childq, p, child_next);
+    release(&initproc->lock);
  }

  // Parent might be sleeping in wait().
+  acquire(&proc->lock);
+
  cv_wakeup(&proc->parent->cv);

  if (wakeupinit)
    cv_wakeup(&initproc->cv); 

-  acquire(&proc->lock); 
-
  // Jump into the scheduler, never to return.
  proc->state = ZOMBIE;
  sched();