Re: [Qemu-devel] [PATCH v2] slirp: fix packet requeue issue in batchq

[Jan Kiszka]

On 2012-02-16 09:45, Zhi Yong Wu wrote:
> On Thu, Feb 16, 2012 at 4:37 PM, Jan Kiszka <address@hidden> wrote:
>> On 2012-02-16 09:07, address@hidden wrote:
>>> From: Zhi Yong Wu <address@hidden>
>>>
>>
>> Please summarize in a bit more details what was broken.
> Should those bits be put in the message part of this part? or here?

Here, as a commit log.

> 
>>
>>> Signed-off-by: Zhi Yong Wu <address@hidden>
>>> ---
>>>  slirp/if.c   |   19 +++++++++++++++++--
>>>  slirp/mbuf.c |    3 +--
>>>  2 files changed, 18 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/slirp/if.c b/slirp/if.c
>>> index 8e0cac2..57350d5 100644
>>> --- a/slirp/if.c
>>> +++ b/slirp/if.c
>>> @@ -22,6 +22,7 @@ ifs_remque(struct mbuf *ifm)
>>>  {
>>>       ifm->ifs_prev->ifs_next = ifm->ifs_next;
>>>       ifm->ifs_next->ifs_prev = ifm->ifs_prev;
>>> +        ifs_init(ifm);
>>>  }
>>>
>>>  void
>>> @@ -154,7 +155,7 @@ if_start(Slirp *slirp)
>>>  {
>>>      uint64_t now = qemu_get_clock_ns(rt_clock);
>>>      int requeued = 0;
>>> -     struct mbuf *ifm, *ifqt;
>>> +    struct mbuf *ifm, *ifqt, *ifm_next;
>>>
>>>       DEBUG_CALL("if_start");
>>>
>>> @@ -162,6 +163,8 @@ if_start(Slirp *slirp)
>>>          return; /* Nothing to do */
>>>
>>>   again:
>>> +        ifm_next = NULL;
>>> +
>>>          /* check if we can really output */
>>>          if (!slirp_can_output(slirp->opaque))
>>>              return;
>>> @@ -190,6 +193,7 @@ if_start(Slirp *slirp)
>>>       /* If there are more packets for this session, re-queue them */
>>>       if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
>>>               insque(ifm->ifs_next, ifqt);
>>> +                ifm_next = ifm->ifs_next;
>>>               ifs_remque(ifm);
>>>       }
>>>
>>> @@ -209,7 +213,18 @@ if_start(Slirp *slirp)
>>>                  m_free(ifm);
>>>              } else {
>>>                  /* re-queue */
>>> -                insque(ifm, ifqt);
>>> +                if (ifm_next) {
>>> +                    /*restore the original state of batchq*/
>>> +                    remque(ifm_next);
>>> +                    insque(ifm, ifqt);
>>> +                    ifm_next->ifs_prev->ifs_next = ifm;
>>> +                    ifm->ifs_prev = ifm_next->ifs_prev;
>>> +                    ifm->ifs_next = ifm_next;
>>> +                    ifm_next->ifs_prev = ifm;
>>> +                } else {
>>> +                    insque(ifm, ifqt);
>>> +                }
>>> +
>>>                  requeued++;
>>>              }
>>>          }
>>> diff --git a/slirp/mbuf.c b/slirp/mbuf.c
>>> index c699c75..f429c0a 100644
>>> --- a/slirp/mbuf.c
>>> +++ b/slirp/mbuf.c
>>> @@ -68,8 +68,7 @@ m_get(Slirp *slirp)
>>>       m->m_size = SLIRP_MSIZE - offsetof(struct mbuf, m_dat);
>>>       m->m_data = m->m_dat;
>>>       m->m_len = 0;
>>> -        m->m_nextpkt = NULL;
>>> -        m->m_prevpkt = NULL;
>>> +        ifs_init(m);
>>>          m->arp_requested = false;
>>>          m->expiration_date = (uint64_t)-1;
>>>  end_error:
>>
>> Wondering now: Is this hunk required or a cleanup?
> The former. I think that the pointer of one raw mbuf which are used to
> link the packets for the same session should default to itself, not
> NULL.

OK. Out of curiosity, is that an older issue or just related to the
requeuing we now practice?

Jan

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