On Mon, 2014-06-02 at 12:00 -0400, Mikulas Patocka wrote: > If you write to some variable with ACCESS_ONCE and use cmpxchg or xchg at > the same time, you break it. ACCESS_ONCE doesn't take the hashed spinlock, > so, in this case, cmpxchg or xchg isn't really atomic at all. So if the problem is using ACCESS_ONCE writes with cmpxchg and xchg at the same time, would the below change address this problem? ----- diff --git a/kernel/locking/mcs_spinlock.c b/kernel/locking/mcs_spinlock.c index 838dc9e..8396721 100644 --- a/kernel/locking/mcs_spinlock.c +++ b/kernel/locking/mcs_spinlock.c @@ -71,7 +71,7 @@ bool osq_lock(struct optimistic_spin_queue **lock) if (likely(prev == NULL)) return true; - ACCESS_ONCE(prev->next) = node; + xchg(&prev->next, node); /* * Normally @prev is untouchable after the above store; because at that @@ -144,7 +144,7 @@ unqueue: */ ACCESS_ONCE(next->prev) = prev; - ACCESS_ONCE(prev->next) = next; + xchg(&prev->next, next); return false; } -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
