[dpdk-dev] [PATCH 1/3] eal/arm64: remove the braces {} for dmb(), dsb()

[Ananyev, Konstantin]

> -----Original Message-----
> From: Jianbo Liu [mailto:jianbo.liu at arm.com]
> Sent: Thursday, November 9, 2017 9:58 AM
> To: Ananyev, Konstantin <konstantin.ananyev at intel.com>
> Cc: Jia He <hejianet at gmail.com>; Richardson, Bruce <bruce.richardson at intel.com>; jerin.jacob at caviumnetworks.com; dev at dpdk.org;
> olivier.matz at 6wind.com; hemant.agrawal at nxp.com; jia.he at hxt-semitech.com
> Subject: Re: [PATCH 1/3] eal/arm64: remove the braces {} for dmb(),dsb()
> 
> The 11/09/2017 09:38, Ananyev, Konstantin wrote:
> >
> >
> > > -----Original Message-----
> > > From: Jianbo Liu [mailto:jianbo.liu at arm.com]
> > > Sent: Thursday, November 9, 2017 4:56 AM
> > > To: Jia He <hejianet at gmail.com>
> > > Cc: Richardson, Bruce <bruce.richardson at intel.com>; jerin.jacob at caviumnetworks.com; dev at dpdk.org; olivier.matz at 6wind.com;
> > > Ananyev, Konstantin <konstantin.ananyev at intel.com>; hemant.agrawal at nxp.com; jia.he at 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 at gmail.com>
> > > > >>>>>Signed-off-by: jia.he at 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...
> 
> I think there is no any issue if we add {} for if/else sections.
> 
> -       if (enqueue)
> +       if (enqueue) {
>                 rte_smp_wmb();
> -       else
> +       } else {
>                 rte_smp_rmb();
> +       }
> 
> It's not a good way to ommit {}.

That's the preferred DPDK coding style these days :)
http://dpdk.org/doc/guides-16.04/contributing/coding_style.html
1.6.2. Control Statements and Loops

Include a space after keywords (if, while, for, return, switch).
Do not use braces ({ and }) for control statements with zero or just a single statement, unless that statement is more than a single line in which case the braces are permitted.

Konstantin

> 
> Jianbo
> 
> > Why not to convert these macros into 'always_inline' functions then?
> > Konstantin
> >
> > >
> > > Jianbo
> > > IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the
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> 
> --
> IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the
> intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or
> store or copy the information in any medium. Thank you.