Re: [PATCH] - Fix memory ordering problem in wake_futex()

[Olof Johansson]

On Fri, Dec 23, 2005 at 03:32:16PM -0600, Jack Steiner wrote:

> On IA64, the "sync" instructions are actually part of the ld.acq ot st.rel
> instructions that are used to set/clear spinlocks.
[...]
> IA64 implements fencing of ld.acq or st.rel instructions as one-directional
> barriers.

So ia64 spin_unlock doesn't do store-store ordering across it. I'm
surprised this is the first time this causes problems. Other architectures
seem to order:

* sparc64 does a membar StoreStore|LoadStore
* powerpc does lwsync or sync, depending on arch
* alpha does an mb();

* x86 is in-order

So, sounds to me like you need to fix your lock primitives, not add
barriers to generic code?


-Olof
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/