[dpdk-dev] [PATCH v2 1/5] lib/stack: fix inconsistent weak / strong cas

[Eads, Gage]

> -----Original Message-----
> From: David Marchand <david.marchand at redhat.com>
> Sent: Monday, September 28, 2020 5:23 AM
> To: Steven Lariau <steven.lariau at arm.com>; Eads, Gage <gage.eads at intel.com>
> Cc: Olivier Matz <olivier.matz at 6wind.com>; dev <dev at dpdk.org>; nd
> <nd at arm.com>
> Subject: Re: [dpdk-dev] [PATCH v2 1/5] lib/stack: fix inconsistent weak / strong
> cas
> 
> On Fri, Sep 25, 2020 at 7:44 PM Steven Lariau <steven.lariau at arm.com> wrote:
> >
> > Fix cmpexchange usage of weak / strong.
> > The generated code is the same on x86 and ARM (there is no weak
> > cmpexchange), but the old usage was inconsistent.
> > For push and pop update size, weak is used because cmpexchange is inside
> > a loop.
> > For pop update root, strong is used even though cmpexchange is inside a
> > loop, because there may be a lot of operations to do in a loop iteration
> > (locate the new head).
> 
> Is this patch backport material?

It's not a bugfix. It could help performance on a system with weak
cmpexchange -- e.g. the pop-update change would ensure no spurious
failures (which the code can handle, but would require another relatively
expensive pass through the pop loop.)

Thanks,
Gage