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Date: Wed, 30 Mar 2022 04:24:55 -0700
From: Tyler Retzlaff <roretzla@linux.microsoft.com>
To: Morten =?iso-8859-1?Q?Br=F8rup?= <mb@smartsharesystems.com>
Cc: Mattias =?iso-8859-1?Q?R=F6nnblom?= <mattias.ronnblom@ericsson.com>,
 dev@dpdk.org, Thomas Monjalon <thomas@monjalon.net>,
 David Marchand <david.marchand@redhat.com>, onar.olsen@ericsson.com,
 Honnappa.Nagarahalli@arm.com, nd@arm.com,
 konstantin.ananyev@intel.com, stephen@networkplumber.org,
 Ola Liljedahl <ola.liljedahl@arm.com>
Subject: Re: [PATCH] eal: add seqlock
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On Wed, Mar 30, 2022 at 12:50:42PM +0200, Morten Brørup wrote:
> > From: Mattias Rönnblom [mailto:mattias.ronnblom@ericsson.com]
> > Sent: Wednesday, 30 March 2022 12.07
> 
> > +
> > +/**
> > + * The RTE seqlock type.
> > + */
> > +typedef struct {
> > +	uint32_t sn; /**< A generation number for the protected data. */
> > +	rte_spinlock_t lock; /**< Spinlock used to serialize writers.  */
> > +} rte_seqlock_t;
> > +
> 
> You refer to 'sn' as the sequence number everywhere else, so please document is as such:
> "/**< Sequence number for the protected data. */"
> 
> Also, consider making 'sn' volatile, although it is only accessed through the __atomic_load_n() function. I don't know if it makes any difference, so I'm just bringing this to the attention of the experts!

i don't think there is value added by cv-volatile qualification.
if we want correct/portable behavior for all targets then we should
just access with appropriate atomics builtins/intrinsics they will
be qualifying volatile and generating correct barriers when
necessary.

> 
> Acked-by: Morten Brørup <mb@smartsharesystems.com>
>