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Date: Thu, 17 Aug 2023 12:14:08 -0700
From: Tyler Retzlaff <roretzla@linux.microsoft.com>
To: Morten =?iso-8859-1?Q?Br=F8rup?= <mb@smartsharesystems.com>
Cc: dev@dpdk.org, techboard@dpdk.org,
Bruce Richardson <bruce.richardson@intel.com>,
Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>,
Ruifeng Wang <ruifeng.wang@arm.com>, Jerin Jacob <jerinj@marvell.com>,
Sunil Kumar Kori <skori@marvell.com>,
Mattias =?iso-8859-1?Q?R=F6nnblom?= <mattias.ronnblom@ericsson.com>,
Joyce Kong <joyce.kong@arm.com>,
David Christensen <drc@linux.vnet.ibm.com>,
Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>,
David Hunt <david.hunt@intel.com>, Thomas Monjalon <thomas@monjalon.net>,
David Marchand <david.marchand@redhat.com>
Subject: Re: [PATCH v4 6/6] devtools: forbid new direct use of GCC atomic
builtins
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On Thu, Aug 17, 2023 at 01:57:01PM +0200, Morten Brørup wrote:
> > From: Tyler Retzlaff [mailto:roretzla@linux.microsoft.com]
> > Sent: Wednesday, 16 August 2023 23.39
> >
> > Refrain from using compiler __atomic_xxx builtins DPDK now requires
> > the use of rte_atomic_<op>_explicit macros when operating on DPDK
> > atomic variables.
>
> There is probably no end to how much can be added to checkpatches.
>
> You got the important stuff, so below are only further suggestions!
>
> [...]
>
> > - # refrain from using compiler __atomic_{add,and,nand,or,sub,xor}_fetch()
> > + # refrain from using compiler __atomic_xxx builtins
> > awk -v FOLDERS="lib drivers app examples" \
> > - -v EXPRESSIONS="__atomic_(add|and|nand|or|sub|xor)_fetch\\\(" \
> > + -v EXPRESSIONS="__atomic_.*\\\(" \
> > -v RET_ON_FAIL=1 \
> > - -v MESSAGE='Using __atomic_op_fetch, prefer __atomic_fetch_op' \
> > + -v MESSAGE='Using __atomic_xxx builtins' \
>
> Alternatively:
> -v MESSAGE='Using __atomic_xxx built-ins, prefer rte_atomic_xxx' \
i can adjust the wording as you suggest, no problem
>
> > -f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
> > "$1" || res=1
> >
> > --
> > 1.8.3.1
>
> This could be updated too:
>
> # refrain from using compiler __atomic_thread_fence()
> # It should be avoided on x86 for SMP case.
> awk -v FOLDERS="lib drivers app examples" \
> -v EXPRESSIONS="__atomic_thread_fence\\\(" \
> -v RET_ON_FAIL=1 \
> - -v MESSAGE='Using __atomic_thread_fence' \
> + -v MESSAGE='Using __atomic_thread_fence built-in, prefer __rte_atomic_thread_fence' \
> -f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
yeah, i left this one separate i think the advice is actually use
rte_atomic_thread_fence which may be an inline function that uses
__rte_atomic_thread_fence
> "$1" || res=1
>
> You could also add C11 variants of these tests...
> atomic_(load|store|exchange|compare_exchange_(strong|weak)|fetch_(add|sub|and|xor|or|nand)|flag_(test_and_set|clear))[_explicit], and
> atomic_thread_fence.
>
> And a test for using "_Atomic".
direct use would cause early compilation in the CI so it would be caught
fairly early. i'm not sure i want to get into the business of trying to
add redundant (albiet cheaper) earlier checks.
though if there is a general call for this from the reviewers i'll add
them.
>
> -Morten