From: Jia He <hejianet@gmail.com>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: jerin.jacob@caviumnetworks.com, dev@dpdk.org,
olivier.matz@6wind.com, konstantin.ananyev@intel.com,
jianbo.liu@arm.com, hemant.agrawal@nxp.com,
jia.he@hxt-semitech.com
Subject: Re: [dpdk-dev] [PATCH 1/3] eal/arm64: remove the braces {} for dmb(), dsb()
Date: Thu, 9 Nov 2017 09:22:10 +0800 [thread overview]
Message-ID: <9086316b-c16b-c42b-2d85-9b01fa2f66e1@gmail.com> (raw)
In-Reply-To: <20171108102814.GA7552@bricha3-MOBL3.ger.corp.intel.com>
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();
will be like below after precompiling:
if (condition)
asm volatile("dsb " "ld" : : : "memory");;
else
anything();
Then, the same error - error: 'else' without a previous 'if'
If you choose do/while(0), yes, no errors from compiler.
But the checkpatch will report
WARNING: Single statement macros should not use a do {} while (0) loop
#11: FILE: lib/librte_eal/common/include/arch/arm/rte_atomic_64.h:46:
+#define dsb(opt) do { asm volatile("dsb " #opt : : : "memory"); } while (0)
I searched the kernel codes, the marco dsb() didn't use the do/while(0).
Which one do you think is better for dpdk?
Cheers,
Jia
next prev parent reply other threads:[~2017-11-09 1:22 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 [this message]
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
2017-11-10 3:09 ` Jianbo Liu
2017-11-10 10:06 ` Ananyev, Konstantin
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