[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 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...
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
> 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.