Re: [dpdk-dev] [PATCH v2 1/3] eal/arm64: add 128-bit atomic compare exchange

From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: "thomas@monjalon.net" <thomas@monjalon.net>,
	"Phil Yang (Arm Technology China)" <Phil.Yang@arm.com>
Cc: "jerinj@marvell.com" <jerinj@marvell.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	 "hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
	"Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	nd <nd@arm.com>, "gage.eads@intel.com" <gage.eads@intel.com>,
	nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v2 1/3] eal/arm64: add 128-bit atomic compare exchange
Date: Mon, 24 Jun 2019 17:41:07 +0000	[thread overview]
Message-ID: <VE1PR08MB514999646C1EBC7C047DED9F98E00@VE1PR08MB5149.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <22963143.DP9djbVQ2r@xps>

> 
> 24/06/2019 18:12, Honnappa Nagarahalli:
> > > > > +	} else {
> > > > > +		rte_panic("Invalid memory order\n");
> > > >
> > > >
> > > > rte_panic should be removed from library. In this case, I think,
> > > > invalid mo can go for strongest barrier.
> >
> > It is added here to capture programming errors.
> > Memory order can be passed during compilation or during run time.
> > 'rte_panic' supports both of these.
> > Adding code with strongest memory order will mask the programming error.
> 
> An error must return a specific code from the function.
> rte_panic is really forbidden in libraries.
> We are in the process of removing all of them.
Thank you for clarifying.
In this particular use case, the API is similar to '__atomic_compare_exchange' built-in. Users would expect similar behavior. If we are differing from the standard behavior, we should document it in the API definition.
 
> 
>