From: Olof Johansson <olof@lixom.net>
To: Jack Steiner <steiner@sgi.com>
Cc: linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org
Subject: Re: [PATCH] - Fix memory ordering problem in wake_futex()
Date: Fri, 23 Dec 2005 15:59:16 -0600 [thread overview]
Message-ID: <20051223215915.GE24601@pb15.lixom.net> (raw)
In-Reply-To: <20051223213216.GA29541@sgi.com>
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
next prev parent reply other threads:[~2005-12-23 22:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-23 16:38 [PATCH] - Fix memory ordering problem in wake_futex() Jack Steiner
2005-12-23 17:05 ` Joe Seigh
2005-12-23 20:48 ` Olof Johansson
2005-12-23 21:32 ` Jack Steiner
2005-12-23 21:59 ` Olof Johansson [this message]
2005-12-23 23:48 ` Robin Holt
2005-12-24 13:45 ` Jack Steiner
2005-12-24 18:13 ` Olof Johansson
2005-12-27 16:30 ` Jack Steiner
-- strict thread matches above, loose matches on Subject: below --
2005-12-23 22:23 Manfred Spraul
2005-12-23 22:52 ` Manfred Spraul
2005-12-24 3:45 ` Jack Steiner
2005-12-25 16:02 ` Manfred Spraul
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