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commit e7a5b3c5ee2d440892ab7e9bb98ad82efb25219f
parent 0b75a8e8bea4f4c8230daae8d81eda04c19e622c
Author: rsc <rsc>
Date:   Thu,  7 Sep 2006 16:53:49 +0000

comment memory barriers

Diffstat:
Mspinlock.c | 9++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/spinlock.c b/spinlock.c @@ -50,6 +50,10 @@ 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 // Record info about lock acquisition for debugging. @@ -64,13 +68,16 @@ acquire(struct spinlock *lock) void release(struct spinlock *lock) { - if(!holding(lock)) panic("release"); 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 + lock->locked = 0; if(--cpus[cpu()].nlock == 0) sti();