From: Will Deacon <will@kernel.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Marco Elver <elver@google.com>, Boqun Feng <boqun.feng@gmail.com>,
Andrea Parri <parri.andrea@gmail.com>,
Mark Rutland <mark.rutland@arm.com>,
Dmitry Vyukov <dvyukov@google.com>,
kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org
Subject: Re: LKMM: Read dependencies of writes ordered by dma_wmb()?
Date: Tue, 17 Aug 2021 13:28:16 +0100 [thread overview]
Message-ID: <20210817122816.GA12746@willie-the-truck> (raw)
In-Reply-To: <20210816205057.GN4126399@paulmck-ThinkPad-P17-Gen-1>
Just on this bit...
On Mon, Aug 16, 2021 at 01:50:57PM -0700, Paul E. McKenney wrote:
> 5. The dma_mb(), dma_rmb(), and dma_wmb() appear to be specific
> to ARMv8.
These are useful on other architectures too! IIRC, they were added by x86 in
the first place. They're designed to be used with dma_alloc_coherent()
allocations where you're sharing something like a ring buffer with a device
and they guarantee accesses won't be reordered before they become visible
to the device. They _also_ provide the same ordering to other CPUs.
I gave a talk at LPC about some of this, which might help (or might make
things worse...):
https://www.youtube.com/watch?v=i6DayghhA8Q
Ignore the bits about mmiowb() as we got rid of that.
Will
next prev parent reply other threads:[~2021-08-17 12:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-16 10:12 LKMM: Read dependencies of writes ordered by dma_wmb()? Marco Elver
2021-08-16 14:59 ` Alan Stern
2021-08-16 17:23 ` Marco Elver
2021-08-16 19:21 ` Alan Stern
2021-08-16 20:50 ` Paul E. McKenney
2021-08-17 12:14 ` Marco Elver
2021-08-17 12:28 ` Will Deacon [this message]
2021-08-17 13:27 ` Marco Elver
2021-08-17 13:53 ` Paul E. McKenney
2021-08-18 11:39 ` Will Deacon
2021-08-18 23:17 ` Paul E. McKenney
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