linux-kernel - Re: [PATCH 13/17] RISC-V: Add include subdirectory

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Date:   Wed, 7 Jun 2017 14:58:50 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>, olof@...om.net,
        albert@...ive.com, patches@...ups.riscv.org,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH 13/17] RISC-V: Add include subdirectory

On Wed, Jun 07, 2017 at 02:36:27PM +0200, Peter Zijlstra wrote:
> Which (pending the sub confusion) will generate the entire set of:
> 
>  atomic_add, atomic_add_return{_relaxed,_acquire,_release,} atomic_fetch_add{_relaxed,_acquire,_release,}
>  atomic_sub, atomic_sub_return{_relaxed,_acquire,_release,} atomic_fetch_sub{_relaxed,_acquire,_release,}
> 
>  atomic_and, atomic_fetch_and{_relaxed,_acquire,_release,}
>  atomic_or,  atomic_fetch_or{_relaxed,_acquire,_release,}
>  atomic_xor, atomic_fetch_xor{_relaxed,_acquire,_release,}
> 

Another approach would be to override __atomic_op_{acquire,release} and
use things like:

	"FENCE r,rw" -- (load) ACQUIRE
	"FENCE rw,w" -- (store) RELEASE

And then you only need to provide _relaxed atomics.

Also, and I didn't check for that, you need to provide:

smp_load_acquire(), smp_store_release(), atomic_read_acquire(),
atomic_store_release().