Re: RFC: patch to allow lock-free traversal of lists with insertion

From: Paul McKenney (
Date: Tue Oct 09 2001 - 10:28:40 EST

> On Mon, Oct 08, 2001 at 10:56:10PM -0700, David S. Miller wrote:
> > I somehow doubt that you need an IPI to implement the equivalent of
> > "membar #StoreStore" on Alpha. Richard?
> Lol. Of course not. Is someone under the impression that AXP
> designers were smoking crack?

The ones I have talked to showed no signs of having done so. However,
their architecture -does- make it quite challenging for anyone trying to
write lock-free common code, hence all the IPIs.

> "wmb" == "membar #StoreStore".
> "mb" == "membar #Sync".
> See the nice mb/rmb/wmb macros in <asm/system.h>.

OK, if "membar #StoreStore" really is equivalent to "wmb", then
"membar #StoreStore" definitely will -not- do the job required here.
Will "membar #SYNC" allow read-side "membar #ReadRead"s to be omitted,
or does "membar #SYNC" fail to detect when outstanding cache
invalidations complete?

                              Thanx, Paul

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