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[DCCP] ccid3: Perform history operations only after packet has been sent

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This migrates all packet history operations into the routine
 ccid3_hc_tx_packet_sent, thereby removing synchronization problems
 that occur when, as before, the operations are spread over multiple
 routines.
 The following minor simplifications are also applied:
  * several simplifications now follow from this change - several tests
    are now no longer required
  * removal of one unnecessary variable (dp)

Justification:

 Currently packet history operations span two different routines,
 one of which is likely to pass through several iterations of sleeping
 and awakening.
 The first routine, ccid3_hc_tx_send_packet, allocates an entry and
 sets a few fields. The remaining fields are filled in when the second
 routine (which is not within a sleeping context), ccid3_hc_tx_packet_sent,
 is called. This has several strong drawbacks:
  * it is not necessary to split history operations - all fields can be
    filled in by the second routine
  * the first routine is called multiple times, until a packet can be sent,
    and sleeps meanwhile - this causes a lot of difficulties with regard to
    keeping the list consistent
  * since both routines do not have a producer-consumer like synchronization,
    it is very difficult to maintain data across calls to these routines
  * the fact that the routines are called in different contexts (sleeping, not
    sleeping) adds further problems

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This commit is contained in:
Gerrit Renker 2006-12-10 00:09:21 -02:00 committed by David S. Miller
parent e312d100f1
commit c5a1ae9a4c
1 changed files with 9 additions and 29 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

38
net/dccp/ccids/ccid3.c
View file

@ -296,7 +296,6 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
{
struct dccp_sock *dp = dccp_sk(sk);
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
struct dccp_tx_hist_entry *new_packet;
struct timeval now;
suseconds_t delay;
@ -310,21 +309,6 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
if (unlikely(skb->len == 0))
return -EBADMSG;
/* See if last packet allocated was not sent */
new_packet = dccp_tx_hist_head(&hctx->ccid3hctx_hist);
if (new_packet == NULL || new_packet->dccphtx_sent) {
new_packet = dccp_tx_hist_entry_new(ccid3_tx_hist,
GFP_ATOMIC);
if (unlikely(new_packet == NULL)) {
DCCP_WARN("%s, sk=%p, not enough mem to add to history,"
"send refused\n", dccp_role(sk), sk);
return -ENOBUFS;
}
dccp_tx_hist_add_entry(&hctx->ccid3hctx_hist, new_packet);
}
dccp_timestamp(sk, &now);
switch (hctx->ccid3hctx_state) {
@ -380,31 +364,27 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
{
const struct dccp_sock *dp = dccp_sk(sk);
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
struct timeval now;
struct dccp_tx_hist_entry *packet;
BUG_ON(hctx == NULL);
dccp_timestamp(sk, &now);
ccid3_hc_tx_update_s(hctx, len);
packet = dccp_tx_hist_head(&hctx->ccid3hctx_hist);
packet = dccp_tx_hist_entry_new(ccid3_tx_hist, GFP_ATOMIC);
if (unlikely(packet == NULL)) {
DCCP_WARN("packet doesn't exist in history!\n");
return;
}
if (unlikely(packet->dccphtx_sent)) {
DCCP_WARN("no unsent packet in history!\n");
DCCP_CRIT("packet history - out of memory!");
return;
}
dccp_tx_hist_add_entry(&hctx->ccid3hctx_hist, packet);
dccp_timestamp(sk, &now);
packet->dccphtx_tstamp = now;
packet->dccphtx_seqno = dp->dccps_gss;
hctx->ccid3hctx_idle = 0;
packet->dccphtx_rtt = hctx->ccid3hctx_rtt;
packet->dccphtx_sent = 1;
packet->dccphtx_seqno = dccp_sk(sk)->dccps_gss;
packet->dccphtx_rtt = hctx->ccid3hctx_rtt;
packet->dccphtx_sent = 1;
hctx->ccid3hctx_idle = 0;
}
static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)