netdev - [PATCH 7/7] [CCID-3]: Remove dead states

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Message-Id: <1206462011-24907-8-git-send-email-gerrit@erg.abdn.ac.uk>
Date:	Tue, 25 Mar 2008 16:20:11 +0000
From:	Gerrit Renker <gerrit@....abdn.ac.uk>
To:	acme@...hat.com
Cc:	dccp@...r.kernel.org, netdev@...r.kernel.org,
	Gerrit Renker <gerrit@....abdn.ac.uk>
Subject: [PATCH 7/7] [CCID-3]: Remove dead states

This patch is thanks to an investigation by Leandro Sales de Melo and his
colleagues. They worked out two state diagrams which highlight the fact that
the xxx_TERM states in CCID-3/4 are in fact not necessary.

And this can be confirmed by in turn looking at the code: the xxx_TERM states
are only ever set in ccid3_hc_{rx,tx}_exit(). These two functions are part
of the following call chain:

 * ccid_hc_{tx,rx}_exit() are called from ccid_delete() only;
 * ccid_delete() invokes ccid_hc_{tx,rx}_exit() in the way of a destructor:
   after calling ccid_hc_{tx,rx}_exit(), the CCID is released from memory;
 * ccid_delete() is in turn called only by ccid_hc_{tx,rx}_delete();
 * ccid_hc_{tx,rx}_delete() is called only if 
   - feature negotiation failed   (dccp_feat_activate_values()),
   - when changing the RX/TX CCID (to eject the current CCID),
   - when destroying the socket   (in dccp_destroy_sock()).

In other words, when CCID-3 sets the state to xxx_TERM, it is at a time where
no more processing should be going on, hence it is not necessary to introduce
a dedicated exit state - this is implicit when unloading the CCID.

Signed-off-by: Gerrit Renker <gerrit@....abdn.ac.uk>
---
 net/dccp/ccids/ccid3.c |   21 +--------------------
 net/dccp/ccids/ccid3.h |    2 --
 2 files changed, 1 insertion(+), 22 deletions(-)

--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -56,7 +56,6 @@ static const char *ccid3_tx_state_name(e
 	[TFRC_SSTATE_NO_SENT]  = "NO_SENT",
 	[TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
 	[TFRC_SSTATE_FBACK]    = "FBACK",
-	[TFRC_SSTATE_TERM]     = "TERM",
 	};
 
 	return ccid3_state_names[state];
@@ -340,10 +339,6 @@ static int ccid3_hc_tx_send_packet(struc
 			return (u32)delay / 1000L;
 
 		ccid3_hc_tx_update_win_count(hctx, now);
-		break;
-	case TFRC_SSTATE_TERM:
-		DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
-		return -EINVAL;
 	}
 
 	/* prepare to send now (add options etc.) */
@@ -379,10 +374,6 @@ static void ccid3_hc_tx_packet_recv(stru
 	    !(dcb->dccpd_type == DCCP_PKT_ACK ||
 	      dcb->dccpd_type == DCCP_PKT_DATAACK))
 		return;
-	/* ... and only in the established state */
-	if (hctx->state != TFRC_SSTATE_FBACK &&
-	    hctx->state != TFRC_SSTATE_NO_FBACK)
-		return;
 
 	opt_recv = &hctx->options_received;
 	now = ktime_get_real();
@@ -557,9 +548,7 @@ static void ccid3_hc_tx_exit(struct sock
 {
 	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 
-	ccid3_hc_tx_set_state(sk, TFRC_SSTATE_TERM);
 	sk_stop_timer(sk, &hctx->no_feedback_timer);
-
 	tfrc_tx_hist_purge(&hctx->hist);
 }
 
@@ -618,7 +607,6 @@ static const char *ccid3_rx_state_name(e
 	static char *ccid3_rx_state_names[] = {
 	[TFRC_RSTATE_NO_DATA] = "NO_DATA",
 	[TFRC_RSTATE_DATA]    = "DATA",
-	[TFRC_RSTATE_TERM]    = "TERM",
 	};
 
 	return ccid3_rx_state_names[state];
@@ -644,14 +632,9 @@ static void ccid3_hc_rx_send_feedback(st
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
 	struct dccp_sock *dp = dccp_sk(sk);
-	ktime_t now;
+	ktime_t now = ktime_get_real();
 	s64 delta = 0;
 
-	if (unlikely(hcrx->state == TFRC_RSTATE_TERM))
-		return;
-
-	now = ktime_get_real();
-
 	switch (fbtype) {
 	case CCID3_FBACK_INITIAL:
 		hcrx->x_recv = 0;
@@ -855,8 +838,6 @@ static void ccid3_hc_rx_exit(struct sock
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
 
-	ccid3_hc_rx_set_state(sk, TFRC_RSTATE_TERM);
-
 	tfrc_rx_hist_purge(&hcrx->hist);
 	tfrc_lh_cleanup(&hcrx->li_hist);
 }
--- a/net/dccp/ccids/ccid3.h
+++ b/net/dccp/ccids/ccid3.h
@@ -72,7 +72,6 @@ enum ccid3_hc_tx_states {
 	TFRC_SSTATE_NO_SENT = 1,
 	TFRC_SSTATE_NO_FBACK,
 	TFRC_SSTATE_FBACK,
-	TFRC_SSTATE_TERM,
 };
 
 /** struct ccid3_hc_tx_sock - CCID3 sender half-connection socket
@@ -127,7 +126,6 @@ static inline struct ccid3_hc_tx_sock *c
 enum ccid3_hc_rx_states {
 	TFRC_RSTATE_NO_DATA = 1,
 	TFRC_RSTATE_DATA,
-	TFRC_RSTATE_TERM    = 127,
 };
 
 /** struct ccid3_hc_rx_sock - CCID3 receiver half-connection socket
--
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