From: Jia He <hejianet@gmail.com>
To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
Jianbo Liu <jianbo.liu@arm.com>
Cc: "Richardson, Bruce" <bruce.richardson@intel.com>,
"jerin.jacob@caviumnetworks.com" <jerin.jacob@caviumnetworks.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
"hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
"jia.he@hxt-semitech.com" <jia.he@hxt-semitech.com>
Subject: Re: [dpdk-dev] [PATCH 1/3] eal/arm64: remove the braces {} for dmb(), dsb()
Date: Fri, 10 Nov 2017 10:06:14 +0800 [thread overview]
Message-ID: <baf39215-8213-e581-8668-164237c895a5@gmail.com> (raw)
In-Reply-To: <2601191342CEEE43887BDE71AB9772585FABB311@irsmsx105.ger.corp.intel.com>
On 11/9/2017 5:38 PM, Ananyev, Konstantin Wrote:
>
>> -----Original Message-----
>> From: Jianbo Liu [mailto:jianbo.liu@arm.com]
>> Sent: Thursday, November 9, 2017 4:56 AM
>> To: Jia He <hejianet@gmail.com>
>> Cc: Richardson, Bruce <bruce.richardson@intel.com>; jerin.jacob@caviumnetworks.com; dev@dpdk.org; olivier.matz@6wind.com;
>> Ananyev, Konstantin <konstantin.ananyev@intel.com>; hemant.agrawal@nxp.com; jia.he@hxt-semitech.com
>> Subject: Re: [PATCH 1/3] eal/arm64: remove the braces {} for dmb(),dsb()
>>
>> The 11/09/2017 12:43, Jia He wrote:
>>> Hi Jianbo
>>>
>>>
>>> On 11/9/2017 11:21 AM, Jianbo Liu Wrote:
>>>> The 11/09/2017 11:14, Jia He wrote:
>>>>> On 11/9/2017 9:22 AM, Jia He Wrote:
>>>>>> Hi Bruce
>>>>>>
>>>>>>
>>>>>> On 11/8/2017 6:28 PM, Bruce Richardson Wrote:
>>>>>>> On Wed, Nov 08, 2017 at 06:17:10AM +0000, Jia He wrote:
>>>>>>>> for the code as follows:
>>>>>>>> if (condition)
>>>>>>>> rte_smp_rmb();
>>>>>>>> else
>>>>>>>> rte_smp_wmb();
>>>>>>>> Without this patch, compiler will report this error:
>>>>>>>> error: 'else' without a previous 'if'
>>>>>>>>
>>>>>>>> Signed-off-by: Jia He <hejianet@gmail.com>
>>>>>>>> Signed-off-by: jia.he@hxt-semitech.com
>>>>>>>> ---
>>>>>>>> lib/librte_eal/common/include/arch/arm/rte_atomic_64.h | 4 ++--
>>>>>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>>>>>
>>>>>>>> diff --git
>>>>>>>> a/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h
>>>>>>>> b/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h
>>>>>>>> index 0b70d62..38c3393 100644
>>>>>>>> --- a/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h
>>>>>>>> +++ b/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h
>>>>>>>> @@ -43,8 +43,8 @@ extern "C" {
>>>>>>>> #include "generic/rte_atomic.h"
>>>>>>>> -#define dsb(opt) { asm volatile("dsb " #opt : : : "memory"); }
>>>>>>>> -#define dmb(opt) { asm volatile("dmb " #opt : : : "memory"); }
>>>>>>>> +#define dsb(opt) asm volatile("dsb " #opt : : : "memory");
>>>>>>>> +#define dmb(opt) asm volatile("dmb " #opt : : : "memory");
>>>>>>> Need to remove the trailing ";" I too I think.
>>>>>>> Alternatively, to keep the braces, the standard practice is to use
>>>>>>> do { ... } while(0)
>>>>>> If trailing ";" is not removed
>>>>>> the code:
>>>>>> if (condition)
>>>>>> rte_smp_rmb();
>>>>>> else
>>>>>> anything();
>>>>>>
>>>> Sorry, why not use two different functions as your conditions passed in
>>>> are fixed in the calling functions.
>>> Do you mean to split update_tail() into update_tail_enqueue() and
>>> update_tail_dequeue()?
>> Yes. So it's not need to change dsb/dmb.
> That's a good idea - but you still might hit the same problem in
> Some different place in future...
> Why not to convert these macros into 'always_inline' functions then?
> Konstantin
>
It makes things more complex
opt needs to be redefined with types
such as : __attribute__((always_inline)) void dsb( char* opt)
and the input paramenter shoud be
#define sy "sy"
#define ld "ld"
And the "#" in asm codes needs to be considerred more.
IMO, the kernel way is simple and clean, isn't it?
#define dmb(opt) asm volatile("dmb " #opt : : : "memory")
Another choice is adding the do/while.
@Ananyev @Jianbo
Any thoughts?
--
Cheers,
Jia
next prev parent reply other threads:[~2017-11-10 2:06 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-08 6:17 Jia He
2017-11-08 6:17 ` [dpdk-dev] [PATCH 2/3] ring: guarantee load ordering of cons/prod when doing enqueue/dequeue Jia He
2017-11-08 7:27 ` Jerin Jacob
2017-11-08 9:49 ` Ananyev, Konstantin
2017-11-08 6:17 ` [dpdk-dev] [PATCH 3/3] config: support C11 memory model for arm64 Jia He
2017-11-08 7:17 ` [dpdk-dev] [PATCH 1/3] eal/arm64: remove the braces {} for dmb(), dsb() Jerin Jacob
2017-11-08 10:28 ` Bruce Richardson
2017-11-09 1:22 ` Jia He
2017-11-09 3:14 ` Jia He
2017-11-09 3:21 ` Jianbo Liu
2017-11-09 4:43 ` Jia He
2017-11-09 4:56 ` Jianbo Liu
2017-11-09 9:38 ` Ananyev, Konstantin
2017-11-09 9:58 ` Jianbo Liu
2017-11-09 10:08 ` Ananyev, Konstantin
2017-11-10 2:06 ` Jia He [this message]
2017-11-10 3:09 ` Jianbo Liu
2017-11-10 10:06 ` Ananyev, Konstantin
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