diff options
Diffstat (limited to 'spinlock.c')
| -rw-r--r-- | spinlock.c | 13 |
1 files changed, 6 insertions, 7 deletions
@@ -51,10 +51,9 @@ acquire(struct spinlock *lock) while(cmpxchg(0, 1, &lock->locked) == 1) ; - // Now that lock is acquired, make sure - // we wait for all pending writes from other - // processors. - cpuid(0, 0, 0, 0, 0); // memory barrier + // Serialize instructions: now that lock is acquired, make sure + // we wait for all pending writes from other processors. + cpuid(0, 0, 0, 0, 0); // memory barrier (see Ch 7 of IA-32 manual, vol 3) // Record info about lock acquisition for debugging. // The +10 is only so that we can tell the difference @@ -74,9 +73,9 @@ release(struct spinlock *lock) lock->pcs[0] = 0; lock->cpu = 0xffffffff; - // Before unlocking the lock, make sure to flush - // any pending memory writes from this processor. - cpuid(0, 0, 0, 0, 0); // memory barrier + // Serialize instructions: before unlocking the lock, make sure + // to flush any pending memory writes from this processor. + cpuid(0, 0, 0, 0, 0); // memory barrier (see Ch 7 of IA-32 manual, vol 3) lock->locked = 0; if(--cpus[cpu()].nlock == 0) |