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Date: Fri, 4 Aug 2017 03:50:05 +1000
From: Nicholas Piggin <npiggin@gmail.com>
To: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: mpe@ellerman.id.au, benh@kernel.crashing.org, anton@samba.org,
 paulus@samba.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v9 14/14] powerpc: rewrite local_t using soft_irq
Message-ID: <20170804035005.1d462325@roar.ozlabs.ibm.com>
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On Thu,  3 Aug 2017 09:19:18 +0530
Madhavan Srinivasan <maddy@linux.vnet.ibm.com> wrote:

> @@ -14,6 +17,202 @@ typedef struct
>  #define local_read(l)	atomic_long_read(&(l)->a)
>  #define local_set(l,i)	atomic_long_set(&(l)->a, (i))
>  
> +#ifdef CONFIG_PPC64
> +
> +static __inline__ void local_add(long i, local_t *l)
> +{
> +	long t;
> +	unsigned long flags;
> +
> +	powerpc_local_irq_pmu_save(flags);
> +	__asm__ __volatile__(
> +	PPC_LL" %0,0(%2)\n\
> +	add	%0,%1,%0\n"
> +	PPC_STL" %0,0(%2)\n"
> +	: "=&r" (t)
> +	: "r" (i), "r" (&(l->a.counter)));
> +	powerpc_local_irq_pmu_restore(flags);
> +}

Hey, so... why are any of these implemented in asm? We should
just do them all in C, right? I looked a bit harder at code gen
and a couple of them are still emitting larx/stcx.

> +
> +#define local_cmpxchg(l, o, n) \
> +	(cmpxchg_local(&((l)->a.counter), (o), (n)))
> +#define local_xchg(l, n) (xchg_local(&((l)->a.counter), (n)))

e.g., these.

Thanks,
Nick