Re: [PATCH v3 01/10] devargs: introduce iterator

["Gaëtan Rivet" <gaetan.rivet@6wind.com>]

Hello Jianfeng,

On Wed, Mar 21, 2018 at 01:43:49PM +0800, Tan, Jianfeng wrote:
> Hi Gaetan,
> 
> 
> On 3/21/2018 7:20 AM, Gaetan Rivet wrote:
> > In preparation to making devargs_list private.
> > 
> > Bus drivers generally need to access rte_devargs pertaining to their
> > operations. This match is a common operation for bus drivers.
> > 
> > Add a new accessor for the rte_devargs list.
> > 
> > Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
> > ---
> >   lib/librte_eal/common/eal_common_devargs.c  | 20 ++++++++++++++++++++
> >   lib/librte_eal/common/include/rte_devargs.h | 20 ++++++++++++++++++++
> >   lib/librte_eal/rte_eal_version.map          |  1 +
> >   3 files changed, 41 insertions(+)
> > 
> > diff --git a/lib/librte_eal/common/eal_common_devargs.c b/lib/librte_eal/common/eal_common_devargs.c
> > index 810b3e18f..c6c5eabcf 100644
> > --- a/lib/librte_eal/common/eal_common_devargs.c
> > +++ b/lib/librte_eal/common/eal_common_devargs.c
> > @@ -207,3 +207,23 @@ rte_eal_devargs_dump(FILE *f)
> >   			devargs->name, devargs->args);
> >   	}
> >   }
> > +
> > +/* bus-aware rte_devargs iterator. */
> > +__rte_experimental
> > +struct rte_devargs *
> > +rte_eal_devargs_next(const char *busname, const struct rte_devargs *start)
> > +{
> > +	struct rte_devargs *da;
> > +
> > +	if (start != NULL)
> > +		da = TAILQ_NEXT(start, next);
> > +	else
> > +		da = TAILQ_FIRST(&devargs_list);
> > +	while (da != NULL) {
> > +		if (busname == NULL ||
> > +		    (strcmp(busname, da->bus->name) == 0))
> > +			return da;
> > +		da = TAILQ_NEXT(da, next);
> > +	}
> > +	return NULL;
> > +}
> > diff --git a/lib/librte_eal/common/include/rte_devargs.h b/lib/librte_eal/common/include/rte_devargs.h
> > index 84e5e23c4..969a10449 100644
> > --- a/lib/librte_eal/common/include/rte_devargs.h
> > +++ b/lib/librte_eal/common/include/rte_devargs.h
> > @@ -189,6 +189,26 @@ rte_eal_devargs_type_count(enum rte_devtype devtype);
> >    */
> >   void rte_eal_devargs_dump(FILE *f);
> > +/**
> > + * Find next rte_devargs matching the provided bus name.
> > + *
> > + * @param busname
> > + *   Limit the iteration to devargs related to buses
> > + *   matching this name.
> > + *   Will return any next rte_devargs if NULL.
> > + *
> > + * @param start
> > + *   Starting iteration point. The iteration will start at
> > + *   the first rte_devargs if NULL.
> > + *
> > + * @return
> > + *   Next rte_devargs entry matching the requested bus,
> > + *   NULL if there is none.
> > + */
> > +__rte_experimental
> > +struct rte_devargs *
> > +rte_eal_devargs_next(const char *busname, const struct rte_devargs *start);
> > +
> >   #ifdef __cplusplus
> >   }
> >   #endif
> > diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
> > index d12360235..02a040a8b 100644
> > --- a/lib/librte_eal/rte_eal_version.map
> > +++ b/lib/librte_eal/rte_eal_version.map
> > @@ -216,6 +216,7 @@ EXPERIMENTAL {
> >   	rte_eal_cleanup;
> >   	rte_eal_devargs_insert;
> > +	rte_eal_devargs_next;
> >   	rte_eal_devargs_parse;
> >   	rte_eal_devargs_remove;
> >   	rte_eal_hotplug_add;
> 
> Shall we change these APIs to be thread-safe?

It was not planned, but I think you raise an interesting point.

At the moment, most devargs operations are happening when a single
thread is started (eal init).

However, hotplug means having insertion and deletion possibly happening
in additional threads. This API exists and could help making these
operations thread-safe.

So this is low-priority I think for now (unless shown otherwise), but
definitely something to look into.

-- 
Gaëtan Rivet
6WIND