[PATCH] tcp: avoid bogus warning in tcp_clean_rtx_queue

From	Arnd Bergmann <arnd@arndb.de>
Newsgroups	linux.kernel
Subject	[PATCH] tcp: avoid bogus warning in tcp_clean_rtx_queue
Date	2017-09-18 22:50 +0200
Message-ID	<urb9o-2X2-7@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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gcc-4.9 warns that it cannot trace the state of the 'last_ackt'
variable since the change to the TCP timestamping code, when
CONFIG_PROFILE_ANNOTATED_BRANCHES is set:

net/ipv4/tcp_input.c: In function 'tcp_clean_rtx_queue':
include/net/tcp.h:757:23: error: 'last_ackt' may be used uninitialized in this function [-Werror=maybe-uninitialized]

Other gcc versions, both older and newer do now show this
warning. Removing the 'likely' annotation makes it go away,
and has no effect on the object code without
CONFIG_PROFILE_ANNOTATED_BRANCHES, as tested with gcc-4.9
and gcc-7.1.1, so this seems to be a safe workaround.

Fixes: 9a568de4818d ("tcp: switch TCP TS option (RFC 7323) to 1ms clock")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 net/ipv4/tcp_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c5d7656beeee..c52bc8e35d4d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3173,7 +3173,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 	if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
 		flag |= FLAG_SACK_RENEGING;
 
-	if (likely(first_ackt) && !(flag & FLAG_RETRANS_DATA_ACKED)) {
+	if (first_ackt && !(flag & FLAG_RETRANS_DATA_ACKED)) {
 		seq_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, first_ackt);
 		ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, last_ackt);
 	}
-- 
2.9.0

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[PATCH] tcp: avoid bogus warning in tcp_clean_rtx_queue Arnd Bergmann <arnd@arndb.de> - 2017-09-18 22:50 +0200
  Re: [PATCH] tcp: avoid bogus warning in tcp_clean_rtx_queue David Miller <davem@davemloft.net> - 2017-09-19 23:10 +0200
    Re: [PATCH] tcp: avoid bogus warning in tcp_clean_rtx_queue Arnd Bergmann <arnd@arndb.de> - 2017-09-19 23:40 +0200
      Re: [PATCH] tcp: avoid bogus warning in tcp_clean_rtx_queue David Miller <davem@davemloft.net> - 2017-09-20 00:10 +0200

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