From: Benjamin Herrenschmidt <benh@kernel•crashing.org>
To: Alexander Duyck <alexander.duyck@gmail•com>
Cc: Alexander Duyck <alexander.h.duyck@redhat•com>,
linux-arch@vger•kernel.org, netdev@vger•kernel.org,
linux-kernel@vger•kernel.org, mathieu.desnoyers@polymtl•ca,
peterz@infradead•org, heiko.carstens@de•ibm.com,
mingo@kernel•org, mikey@neuling•org, linux@arm•linux.org.uk,
donald.c.skidmore@intel•com, matthew.vick@intel•com,
geert@linux-m68k•org, jeffrey.t.kirsher@intel•com,
romieu@fr•zoreil.com, paulmck@linux•vnet.ibm.com,
nic_swsd@realtek•com, will.deacon@arm•com,
michael@ellerman•id.au, tony.luck@intel•com,
torvalds@linux-foundation•org, oleg@redhat•com,
schwidefsky@de•ibm.com, fweisbec@gmail•com, davem@davemloft•net
Subject: Re: [PATCH 2/4] arch: Add lightweight memory barriers fast_rmb() and fast_wmb()
Date: Tue, 18 Nov 2014 11:39:27 +1100 [thread overview]
Message-ID: <1416271167.18381.16.camel@kernel.crashing.org> (raw)
In-Reply-To: <546A5968.1090201@gmail.com>
On Mon, 2014-11-17 at 12:24 -0800, Alexander Duyck wrote:
> Yes and no. So for example on ARM I used the dmb() operation, however
> I
> have to use the barrier at the system level instead of just the inner
> shared domain. However on many other architectures they are just the
> same as the smp_* variants.
>
> Basically the resultant code is somewhere between the smp and non-smp
> barriers in terms of what they cover.
There I don't quite follow you. You need to explain better especially in
the documentation because otherwise people will get it wrong...
If it's ordering in the coherent domain, I fail to see how a DMA agent
is different than another processor when it comes to barriers, so I fail
to see the difference with smp_*
I understand the MMIO vs. memory issue, we do have the same on powerpc,
but that other aspect eludes me.
Ben.
next prev parent reply other threads:[~2014-11-18 0:39 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-17 17:17 [PATCH 0/4] Add lightweight memory barriers fast_rmb() and fast_wmb() Alexander Duyck
2014-11-17 17:17 ` [PATCH 1/4] arch: Cleanup read_barrier_depends() and comments Alexander Duyck
2014-11-17 17:18 ` [PATCH 2/4] arch: Add lightweight memory barriers fast_rmb() and fast_wmb() Alexander Duyck
2014-11-17 20:04 ` Benjamin Herrenschmidt
2014-11-17 20:24 ` Alexander Duyck
2014-11-18 0:39 ` Benjamin Herrenschmidt [this message]
2014-11-18 3:13 ` Alexander Duyck
2014-11-18 11:58 ` Will Deacon
2014-11-18 16:20 ` Alexander Duyck
2014-11-18 16:48 ` Will Deacon
2014-11-18 21:07 ` Benjamin Herrenschmidt
2014-11-17 20:18 ` Paul E. McKenney
2014-11-17 21:11 ` Alexander Duyck
2014-11-17 23:17 ` Paul E. McKenney
2014-11-18 3:33 ` Alexander Duyck
2014-11-18 0:38 ` Benjamin Herrenschmidt
2014-11-17 20:52 ` Linus Torvalds
2014-11-17 21:54 ` Alexander Duyck
2014-11-18 0:43 ` Benjamin Herrenschmidt
2014-11-18 0:41 ` Benjamin Herrenschmidt
2014-11-17 17:18 ` [PATCH 3/4] r8169: Use fast_rmb() and fast_wmb() for DescOwn checks Alexander Duyck
2014-11-17 17:18 ` [PATCH 4/4] fm10k/igb/ixgbe: Use fast_rmb on Rx descriptor reads Alexander Duyck
2014-11-17 21:32 ` Jeff Kirsher
2014-11-18 9:57 ` [PATCH 0/4] Add lightweight memory barriers fast_rmb() and fast_wmb() David Laight
2014-11-18 15:44 ` Alexander Duyck
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