i think my cmpxchg use was wrong in acquire

nesting cli/sti: release shouldn't always enable interrupts
separate setup of lapic from starting of other cpus, so cpu() works earlier
flag to disable locking in console output
make locks work even when curproc==0
(still crashes in clock interrupt)

1 files changed, 23 insertions, 9 deletions

diff --git a/spinlock.c b/spinlock.c
index 9f840a8..bd6bff5 100644
--- a/spinlock.c
+++ b/spinlock.c
@@ -8,6 +8,8 @@
 
 #define DEBUG 0
 
+extern use_printf_lock;
+
 int getcallerpc(void *v) {
   return ((int*)v)[-1];
 }
@@ -15,37 +17,49 @@ int getcallerpc(void *v) {
 void
 acquire(struct spinlock * lock)
 {
-  struct proc * cp = curproc[cpu()];
+  unsigned who;
+
+  if(curproc[cpu()])
+    who = (unsigned) curproc[cpu()];
+  else
+    who = cpu() + 1;
 
-  // on a real machine there would be a memory barrier here
   if(DEBUG) cprintf("cpu%d: acquiring at %x\n", cpu(), getcallerpc(&lock));
-  if (cp && lock->p == cp && lock->locked){
+
+  if (lock->who == who && lock->locked){
     lock->count += 1;
   } else { 
     cli();
-    while ( cmpxchg(0, 1, &lock->locked) != 1 ) { ; }
+    // if we get the lock, eax will be zero
+    // if we don't get the lock, eax will be one
+    while ( cmpxchg(0, 1, &lock->locked) == 1 ) { ; }
     lock->locker_pc = getcallerpc(&lock);
     lock->count = 1;
-    lock->p = cp;
+    lock->who = who;
   }
+
   if(DEBUG) cprintf("cpu%d: acquired at %x\n", cpu(), getcallerpc(&lock));
 }
 
 void
 release(struct spinlock * lock)
 {
-  struct proc * cp = curproc[cpu()];
+  unsigned who;
+
+  if(curproc[cpu()])
+    who = (unsigned) curproc[cpu()];
+  else
+    who = cpu() + 1;
 
   if(DEBUG) cprintf ("cpu%d: releasing at %x\n", cpu(), getcallerpc(&lock));
 
-  if(lock->p != cp || lock->count < 1 || lock->locked != 1)
+  if(lock->who != who || lock->count < 1 || lock->locked != 1)
     panic("release");
 
   lock->count -= 1;
   if(lock->count < 1){
-    lock->p = 0;
+    lock->who = 0;
     cmpxchg(1, 0, &lock->locked);
     sti();
-    // on a real machine there would be a memory barrier here
   }
 }