linux-kernel - Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write

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Message-ID: <CA+55aFww9F7DA2V611OjkDyf8nfBVFZkLCu1M243mcj7DKqekA@mail.gmail.com>
Date:	Sat, 18 Jan 2014 16:57:05 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Matt Turner <mattst88@...il.com>,
	Waiman Long <waiman.long@...com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Daniel J Blueman <daniel@...ascale.com>,
	Richard Henderson <rth@...ddle.net>
Subject: Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock()

On Sat, Jan 18, 2014 at 1:22 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
>
> Yes, this requires that -all- updates to the fields in the machine word
> in question use atomic rmw.  Which would not be pretty from a core-code
> perspective.  Hence my suggestion of ceasing Linux-kernel support for
> DEC Alpha CPUs that don't support byte operations.  Also need 16-bit
> operations as well, of course...

I'm not seeing this.

Why the hell would you have byte- or halfword-sized versions of the
store_release or load_acquire things on alpha anyway?

What it means is that data structures that do locking or atomics need
to be "int" or "long" on alpha.  That has always been true. What do
you claim has changed?

                  Linus
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