[PATCH] Remove CPU_32v6K dependencies in asm/spinlock.h

[Catalin Marinas]

On 15 January 2011 16:11, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> SMP requires at least the ARMv6K extensions to be present, so if we're
> running on SMP, the WFE and SEV instructions must be available.
>
> However, when we run on UP, the v6K extensions may not be available,
> and so we don't want WFE/SEV to be in the instruction stream.  Use the
> SMP alternatives infrastructure to replace these instructions with NOPs
> if we build for SMP but run on UP.
[...]
> --- a/arch/arm/include/asm/spinlock.h
> +++ b/arch/arm/include/asm/spinlock.h
> @@ -5,17 +5,36 @@
>  #error SMP not supported on pre-ARMv6 CPUs
>  #endif
>
> +/*
> + * sev and wfe are ARMv6K extensions.  Uniprocessor ARMv6 may not have the K
> + * extensions, so when running on UP, we have to patch these instructions away.
> + */
> +#define ALT_SMP(smp, up)                                       \
> +       "9998:  " smp "\n"                                      \
> +       "       .pushsection \".alt.smp.init\", \"a\"\n"        \
> +       "       .long   9998b\n"                                \
> +       "       " up "\n"                                       \
> +       "       .popsection\n"
> +
> +#ifdef CONFIG_THUMB2_KERNEL
> +#define SEV            ALT_SMP("sev.w", "nop.w")
> +#define WFE(cond)      ALT_SMP("wfe" cond ".w", "nop.w")
> +#else
> +#define SEV            ALT_SMP("sev", "nop")
> +#define WFE(cond)      ALT_SMP("wfe" cond, "nop")
> +#endif

In the SEV macro definition, can you also include the dsb? This
barrier is only there because of sev, otherwise we don't need it (we
have a dmb prior to releasing the lock).

-- 
Catalin