- li a6,1 // lock value
- DISABLE_PREEMPTION()
- lwarx a7,0,a0 // CEMV10
-8:
- sync
- lwarx a7,0,a0 // read the lock
- cmpwi cr0,a7,0 // is it busy?
- bne- 9f // yes, give up
- sync
- stwcx. a6,0,a0 // try to get the lock
- bne- 8b // failed, try again
- li a0,1 // return TRUE
- isync
- blr
-9:
- ENABLE_PREEMPTION()
- li a0,0 // return FALSE
- blr
+ li a6,1 // lock value
+
+ lwz a7,0(a0) // Get lock word
+ mr. a7,a7 // Is it held?
+ bne-- 6f // Yup...
+
+9: lwarx a7,0,a0 // read the lock
+ mr. a7,a7 // Is it held?
+ bne-- 7f // yes, kill reservation
+ stwcx. a6,0,a0 // try to get the lock
+ bne-- 9b // failed, try again
+ li a0,1 // return TRUE
+ isync
+ blr // got it, return
+
+7: li a7,-4 // Point to a spot in the red zone
+ stwcx. a7,a7,r1 // Kill reservation
+
+6:
+ li a0,0 // return FALSE
+ blr
+