On Mon, 2002-02-04 at 23:47, Daniel Jacobowitz wrote: > > Won't this cause some gratuitous thrashing if someone else is trying to > get the spinlock at the same time? > Actually, if you look at the required semantics of ll, no. A ll by itself can never cause a sc from another cpu to fail. It's part of the semantic definition to avoid potential livelock cases, e.g. A does ll B does ll, foiling A's lock attempt A does sc, which fails A does ll, foiling B's lock attempt B does sc, which fails B does ll, foiling A's lock attempt ... Instead, this case becomes: A does ll B does ll A does sc, which succeeds, even though B has done a ll B does sc which fails A does critical section work B spins on ll until A releases the lock -Justin
