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comment memory barriers

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rsc 2006-09-07 16:53:49 +00:00
parent 0b75a8e8be
commit e7a5b3c5ee
1 changed files with 8 additions and 1 deletions
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9
spinlock.c
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@ -50,6 +50,10 @@ acquire(struct spinlock *lock)
while(cmpxchg(0, 1, &lock->locked) == 1) 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 cpuid(0, 0, 0, 0, 0); // memory barrier
// Record info about lock acquisition for debugging. // Record info about lock acquisition for debugging.
@ -64,13 +68,16 @@ acquire(struct spinlock *lock)
void void
release(struct spinlock *lock) release(struct spinlock *lock)
{ {
if(!holding(lock)) if(!holding(lock))
panic("release"); panic("release");
lock->pcs[0] = 0; lock->pcs[0] = 0;
lock->cpu = 0xffffffff; 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 cpuid(0, 0, 0, 0, 0); // memory barrier
lock->locked = 0; lock->locked = 0;
if(--cpus[cpu()].nlock == 0) if(--cpus[cpu()].nlock == 0)
sti(); sti();