diff options
Diffstat (limited to 'spinlock.c')
| -rw-r--r-- | spinlock.c | 16 |
1 files changed, 15 insertions, 1 deletions
@@ -1,3 +1,5 @@ +// Mutual exclusion spin locks. + #include "types.h" #include "defs.h" #include "x86.h" @@ -16,6 +18,7 @@ initlock(struct spinlock *lock, char *name) lock->cpu = 0xffffffff; } +// Record the current call stack in pcs[] by following the %ebp chain. void getcallerpcs(void *v, uint pcs[]) { @@ -31,6 +34,10 @@ getcallerpcs(void *v, uint pcs[]) pcs[i] = 0; } +// Acquire the lock. +// Loops (spins) until the lock is acquired. +// (Because contention is handled by spinning, must not +// go to sleep holding any locks.) void acquire(struct spinlock *lock) { @@ -44,10 +51,16 @@ acquire(struct spinlock *lock) while(cmpxchg(0, 1, &lock->locked) == 1) ; cpuid(0, 0, 0, 0, 0); // memory barrier - getcallerpcs(&lock, lock->pcs); + + // Record info about lock acquisition for debugging. + // The +10 is only so that we can tell the difference + // between forgetting to initialize lock->cpu + // and holding a lock on cpu 0. lock->cpu = cpu() + 10; + getcallerpcs(&lock, lock->pcs); } +// Release the lock. void release(struct spinlock *lock) { @@ -63,6 +76,7 @@ release(struct spinlock *lock) sti(); } +// Check whether this cpu is holding the lock. int holding(struct spinlock *lock) { |