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From: "Wiles, Keith" <keith.wiles@intel.com>
To: "dev@dpdk.org" <dev@dpdk.org>
Thread-Topic: Do we need the refcnt set to zero again?
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Date: Sat, 28 Feb 2015 18:08:16 +0000
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Subject: [dpdk-dev] Do we need the refcnt set to zero again?
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Looking that the code below does the rte_mbuf_refcnt_set(m,0) need to be pr=
esent?

static inline struct rte_mbuf* __attribute__((always_inline))
__rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
{
__rte_mbuf_sanity_check(m, 0);

if (likely (rte_mbuf_refcnt_read(m) =3D=3D 1) ||
likely (rte_mbuf_refcnt_update(m, -1) =3D=3D 0)) {

rte_mbuf_refcnt_set(m, 0);

/* if this is an indirect mbuf, then
*  - detach mbuf
*  - free attached mbuf segment
*/
if (RTE_MBUF_INDIRECT(m)) {
struct rte_mbuf *md =3D RTE_MBUF_FROM_BADDR(m->buf_addr);
rte_pktmbuf_detach(m);
if (rte_mbuf_refcnt_update(md, -1) =3D=3D 0)
__rte_mbuf_raw_free(md);
}
return(m);
}
return (NULL);
}

It seems like the code could be this or did I miss a race-condition?

static inline struct rte_mbuf* __attribute__((always_inline))
__rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
{
__rte_mbuf_sanity_check(m, 0);

/* The sanity check above should have checked for refcnt being zero */
if ( likely (rte_mbuf_refcnt_update(m, -1) =3D=3D 0 ) {

/* if this is an indirect mbuf, then
 *  - detach mbuf
 *  - free attached mbuf segment
 */
if (RTE_MBUF_INDIRECT(m)) {
struct rte_mbuf *md =3D RTE_MBUF_FROM_BADDR(m->buf_addr);
rte_pktmbuf_detach(m);
if (rte_mbuf_refcnt_update(md, -1) =3D=3D 0)
__rte_mbuf_raw_free(md);
}
return(m);
}
return (NULL);
}