Does anyone here understand this bit of code in mb_free_ext()?
/* Free attached storage if this mbuf is the only reference to it. */
if (*(m->m_ext.ref_cnt) == 1 ||
atomic_fetchadd_int(m->m_ext.ref_cnt, -1) == 1) {
switch (m->m_ext.ext_type) {
case EXT_PACKET: /* The packet zone is special. */
if (*(m->m_ext.ref_cnt) == 0)
*(m->m_ext.ref_cnt) = 1;
uma_zfree(zone_pack, m);
return; /* Job done. */
Why would *(m->m_ext.ref_cnt) == 0 be true when the if condition
checks only for ref_cnt to be 1? Should the atomic_fetchadd_int() be
checked for <= 1?
Also, why is the packet zone special? Any history here?
-vijay
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