From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Olof Johansson <olof@lixom.net>,
linuxppc-dev@ozlabs.org, paulus@samba.org
Subject: Re: [PATCH] [2.6.18] U4 DART improvements
Date: Sat, 03 Jun 2006 10:40:38 +1000 [thread overview]
Message-ID: <1149295238.7972.12.camel@localhost.localdomain> (raw)
In-Reply-To: <61e1e9d0ada7e9648b8590cfac2b67b9@kernel.crashing.org>
On Fri, 2006-06-02 at 14:44 +0200, Segher Boessenkool wrote:
> Hi Olof,
>
> Looks good. One request:
>
> > +static inline void dart_tlb_invalidate_one(unsigned long bus_rpn)
> > +{
> > + unsigned int reg;
> > + unsigned int l, limit;
> > +
> > + reg = DART_CNTL_U4_ENABLE | DART_CNTL_U4_IONE |
> > + (bus_rpn & DART_CNTL_U4_IONE_MASK);
> > + DART_OUT(DART_CNTL, reg);
> > + mb();
>
> Could you please comment the memory barriers, to say exactly _why_ a
> certain barrier is needed? I can't see why wmb() wouldn't work here,
> for example (note I'm not saying it would -- I just don't see why it
> wouldn't).
>
> Same goes for every single memory barrier in the whole kernel source
> code, but I have to start somewhere, heh.
In fact I doubt we need a barrier at all...
Ben.
next prev parent reply other threads:[~2006-06-03 0:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-02 4:04 [PATCH] [2.6.18] U4 DART improvements Olof Johansson
2006-06-02 12:44 ` Segher Boessenkool
2006-06-03 0:40 ` Benjamin Herrenschmidt [this message]
2006-06-03 3:28 ` Olof Johansson
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