[DCCP] ccid3: Perform history operations only after packet has been sent (c5a1ae9a) · Commits · 戴 / test

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>

net/dccp/ccids/ccid3.c

+9 −29

Original line number	Diff line number	Diff line
		@@ -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_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)

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