From: vladimir.murzin@arm•com (Vladimir Murzin)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: SWP emulation: Restore original *data when failed
Date: Thu, 15 Oct 2015 10:17:47 +0100 [thread overview]
Message-ID: <561F6F3B.6030607@arm.com> (raw)
In-Reply-To: <20151015085700.GY32532@n2100.arm.linux.org.uk>
On 15/10/15 09:57, Russell King - ARM Linux wrote:
> On Thu, Oct 15, 2015 at 04:36:31PM +0800, Shengjiu Wang wrote:
>> On Thu, Oct 15, 2015 at 09:24:17AM +0100, Russell King - ARM Linux wrote:
>>> On Wed, Oct 14, 2015 at 10:51:17AM +0800, Shengjiu Wang wrote:
>>>> __user_swpX_asm maybe failed in first STREX operation, emulate_swpX
>>>> will try again, but the *data has been changed in first time. which
>>>> cause the result is wrong. So need to recover the *data when failed.
>>>>
>>>> Signed-off-by: Shengjiu Wang <shengjiu.wang@freescale•com>
>>>> ---
>>>> arch/arm/kernel/swp_emulate.c | 1 +
>>>> 1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/arch/arm/kernel/swp_emulate.c b/arch/arm/kernel/swp_emulate.c
>>>> index 5b26e7e..c61fbf92 100644
>>>> --- a/arch/arm/kernel/swp_emulate.c
>>>> +++ b/arch/arm/kernel/swp_emulate.c
>>>> @@ -41,6 +41,7 @@
>>>> "1: strex"B" %0, %2, [%3]\n" \
>>>> " cmp %0, #0\n" \
>>>> " movne %0, %4\n" \
>>>> + " movne %1, %2\n" \
>>>> "2:\n" \
>>>> " .section .text.fixup,\"ax\"\n" \
>>>> " .align 2\n" \
>>>
>>> I think I'd prefer this to be:
>>>
>>> __asm__ __volatile__( \
>>> "0: ldrex"B" %2, [%3]\n" \
>>> "1: strex"B" %0, %1, [%3]\n" \
>>> " cmp %0, #0\n" \
>>> " moveq %1, %2\n" \
>>> " movne %0, %4\n" \
>>>
>>> so that we're not loading into %1 (an in-out non-temporary) but rather
>>> loading it into a temporary - and only overwriting the saved register
>>> value if the swap succeeds.
>>>
>>> Thanks.
>>
>> I am ok with your change. Need I send another patch for this change? or will
>> you send it by yourself?
>
> Please send a new patch, thanks.
>
We might need the same change for arm64 counterpart (see
arch/arm64/kernel/armv8_deprecated.c).
Vladimir
next prev parent reply other threads:[~2015-10-15 9:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-14 2:51 [PATCH] ARM: SWP emulation: Restore original *data when failed Shengjiu Wang
2015-10-15 8:24 ` Russell King - ARM Linux
2015-10-15 8:36 ` Shengjiu Wang
2015-10-15 8:57 ` Russell King - ARM Linux
2015-10-15 9:17 ` Vladimir Murzin [this message]
2015-10-15 13:02 ` Will Deacon
2015-10-15 13:25 ` Vladimir Murzin
2015-10-16 7:52 ` Vladimir Murzin
2015-10-16 10:37 ` Catalin Marinas
2015-10-27 15:44 ` Will Deacon
2015-10-28 16:16 ` Will Deacon
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