Patchwork [2/7] tcp_cubic: fix comparison of jiffies

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Submitter stephen hemminger
Date March 14, 2011, 5:52 p.m.
Message ID <20110314175439.377973202@vyatta.com>
Download mbox | patch
Permalink /patch/86786/
State Accepted
Delegated to: David Miller
Headers show

Comments

stephen hemminger - March 14, 2011, 5:52 p.m.
Jiffies wraps around therefore the correct way to compare is
to use cast to signed value.

Note: cubic is not using full jiffies value on 64 bit arch
because using full unsigned long makes struct bictcp grow too
large for the available ca_priv area.

Includes correction from Sangtae Ha to improve ack train detection.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>




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Patch

--- a/net/ipv4/tcp_cubic.c	2011-03-11 09:00:06.856664687 -0800
+++ b/net/ipv4/tcp_cubic.c	2011-03-11 09:02:11.685796371 -0800
@@ -342,9 +342,11 @@  static void hystart_update(struct sock *
 		u32 curr_jiffies = jiffies;
 
 		/* first detection parameter - ack-train detection */
-		if (curr_jiffies - ca->last_jiffies <= msecs_to_jiffies(2)) {
+		if ((s32)(curr_jiffies - ca->last_jiffies) <=
+		    msecs_to_jiffies(2)) {
 			ca->last_jiffies = curr_jiffies;
-			if (curr_jiffies - ca->round_start >= ca->delay_min>>4)
+			if ((s32) (curr_jiffies - ca->round_start) >
+			    ca->delay_min >> 4)
 				ca->found |= HYSTART_ACK_TRAIN;
 		}