From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V2] arm64: percpu: Make this_cpu accessors pre-empt safe
Date: Mon, 23 Mar 2015 10:17:58 +0000 [thread overview]
Message-ID: <20150323101758.GB11189@arm.com> (raw)
In-Reply-To: <1427035911-10585-1-git-send-email-steve.capper@linaro.org>
On Sun, Mar 22, 2015 at 02:51:51PM +0000, Steve Capper wrote:
> this_cpu operations were implemented for arm64 in:
> 5284e1b arm64: xchg: Implement cmpxchg_double
> f97fc81 arm64: percpu: Implement this_cpu operations
>
> Unfortunately, it is possible for pre-emption to take place between
> address generation and data access. This can lead to cases where data
> is being manipulated by this_cpu for a different CPU than it was
> called on. Which effectively breaks the spec.
>
> This patch disables pre-emption for the this_cpu operations
> guaranteeing that address generation and data manipulation take place
> without a pre-emption in-between.
>
> Fixes: 5284e1b4bc8a ("arm64: xchg: Implement cmpxchg_double")
> Fixes: f97fc810798c ("arm64: percpu: Implement this_cpu operations")
> Reported-by: Mark Rutland <mark.rutland@arm•com>
> Signed-off-by: Steve Capper <steve.capper@linaro•org>
> ---
> Changed in V2, moved over to preempt_enable() completely.
> Corrected the "Fixes" tag.
>
> Mark, I've dropped your Reviewed-by as I've changed some logic, please
> let me know if I should re-add it.
>
> Cheers,
> --
> Steve
> ---
> arch/arm64/include/asm/cmpxchg.h | 32 +++++++++++++++++++++--------
> arch/arm64/include/asm/percpu.h | 44 ++++++++++++++++++++++++++++++----------
> 2 files changed, 57 insertions(+), 19 deletions(-)
>
> diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h
> index cb95930..d8c25b7 100644
> --- a/arch/arm64/include/asm/cmpxchg.h
> +++ b/arch/arm64/include/asm/cmpxchg.h
> @@ -246,14 +246,30 @@ static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old,
> __ret; \
> })
>
> -#define this_cpu_cmpxchg_1(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
> -#define this_cpu_cmpxchg_2(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
> -#define this_cpu_cmpxchg_4(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
> -#define this_cpu_cmpxchg_8(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
> -
> -#define this_cpu_cmpxchg_double_8(ptr1, ptr2, o1, o2, n1, n2) \
> - cmpxchg_double_local(raw_cpu_ptr(&(ptr1)), raw_cpu_ptr(&(ptr2)), \
> - o1, o2, n1, n2)
> +#define _protect_cmpxchg_local(pcp, o, n) \
> +({ \
> + typeof(*raw_cpu_ptr(&(pcp))) __ret; \
> + preempt_disable(); \
> + __ret = cmpxchg_local(raw_cpu_ptr(&(pcp)), o, n); \
> + preempt_enable(); \
> + __ret; \
> +})
> +
> +#define this_cpu_cmpxchg_1(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)
> +#define this_cpu_cmpxchg_2(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)
> +#define this_cpu_cmpxchg_4(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)
> +#define this_cpu_cmpxchg_8(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)
> +
> +#define this_cpu_cmpxchg_double_8(ptr1, ptr2, o1, o2, n1, n2) \
> +({ \
> + int __ret; \
> + preempt_disable(); \
> + __ret = cmpxchg_double_local( raw_cpu_ptr(&(ptr1)), \
Weird whitespace here, but the patch looks fine to me:
Acked-by: Will Deacon <will.deacon@arm•com>
Thanks, Steve.
Will
prev parent reply other threads:[~2015-03-23 10:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-19 14:52 [PATCH] arm64: percpu: Make this_cpu accessors pre-empt safe Steve Capper
2015-03-19 15:44 ` Mark Rutland
2015-03-19 15:55 ` Steve Capper
2015-03-19 16:23 ` Mark Rutland
2015-03-19 16:00 ` Will Deacon
2015-03-19 16:11 ` Mark Rutland
2015-03-19 16:27 ` Will Deacon
2015-03-19 16:39 ` Mark Rutland
2015-03-20 18:02 ` Will Deacon
2015-03-22 14:51 ` [PATCH V2] " Steve Capper
2015-03-23 10:17 ` Will Deacon [this message]
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