hold ptable.lock for the entire process creation

however, processes still modify their own p->* without locking

1 files changed, 13 insertions, 7 deletions

diff --git a/proc.c b/proc.c
index b6dd11f..85f3f17 100644
--- a/proc.c
+++ b/proc.c
@@ -31,23 +31,21 @@ pinit(void)
 // If found, change state to EMBRYO and initialize
 // state required to run in the kernel.
 // Otherwise return 0.
+// Must hold ptable.lock.
 static struct proc*
 allocproc(void)
 {
   struct proc *p;
   char *sp;
 
-  acquire(&ptable.lock);
   for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
     if(p->state == UNUSED)
       goto found;
-  release(&ptable.lock);
   return 0;
 
 found:
   p->state = EMBRYO;
   p->pid = nextpid++;
-  release(&ptable.lock);
 
   // Allocate kernel stack.
   if((p->kstack = kalloc()) == 0){
@@ -81,6 +79,8 @@ userinit(void)
   struct proc *p;
   extern char _binary_initcode_start[], _binary_initcode_size[];
   
+  acquire(&ptable.lock);
+
   p = allocproc();
   initproc = p;
   if((p->pgdir = setupkvm()) == 0)
@@ -100,6 +100,8 @@ userinit(void)
   p->cwd = namei("/");
 
   p->state = RUNNABLE;
+
+  release(&ptable.lock);
 }
 
 // Grow current process's memory by n bytes.
@@ -131,15 +133,20 @@ fork(void)
   int i, pid;
   struct proc *np;
 
+  acquire(&ptable.lock);
+
   // Allocate process.
-  if((np = allocproc()) == 0)
+  if((np = allocproc()) == 0){
+    release(&ptable.lock);
     return -1;
+  }
 
   // Copy process state from p.
   if((np->pgdir = copyuvm(proc->pgdir, proc->sz)) == 0){
     kfree(np->kstack);
     np->kstack = 0;
     np->state = UNUSED;
+    release(&ptable.lock);
     return -1;
   }
   np->sz = proc->sz;
@@ -158,9 +165,8 @@ fork(void)
  
   pid = np->pid;
 
-  // lock to force the compiler to emit the np->state write last.
-  acquire(&ptable.lock);
   np->state = RUNNABLE;
+
   release(&ptable.lock);
   
   return pid;
@@ -233,11 +239,11 @@ wait(void)
         kfree(p->kstack);
         p->kstack = 0;
         freevm(p->pgdir);
-        p->state = UNUSED;
         p->pid = 0;
         p->parent = 0;
         p->name[0] = 0;
         p->killed = 0;
+        p->state = UNUSED;
         release(&ptable.lock);
         return pid;
       }