kern/183659: commit references a PR

[dfilter service]

The following reply was made to PR kern/183659; it has been noted by GNATS.

From: dfilter at FreeBSD.ORG (dfilter service)
To: bug-followup at FreeBSD.org
Cc:  
Subject: Re: kern/183659: commit references a PR
Date: Tue, 28 Jan 2014 20:28:45 +0000 (UTC)

 Author: gnn
 Date: Tue Jan 28 20:28:32 2014
 New Revision: 261242
 URL: http://svnweb.freebsd.org/changeset/base/261242
 
 Log:
   Decrease lock contention within the TCP accept case by removing
   the INP_INFO lock from tcp_usr_accept.  As the PR/patch states
   this was following the advice already in the code.
   See the PR below for a full disucssion of this change and its
   measured effects.
   
   PR:		183659
   Submitted by:	Julian Charbon
   Reviewed by:	jhb
 
 Modified:
   head/sys/netinet/tcp_syncache.c
   head/sys/netinet/tcp_usrreq.c
 
 Modified: head/sys/netinet/tcp_syncache.c
 ==============================================================================
 --- head/sys/netinet/tcp_syncache.c	Tue Jan 28 19:12:31 2014	(r261241)
 +++ head/sys/netinet/tcp_syncache.c	Tue Jan 28 20:28:32 2014	(r261242)
 @@ -682,7 +682,7 @@ syncache_socket(struct syncache *sc, str
  	 * connection when the SYN arrived.  If we can't create
  	 * the connection, abort it.
  	 */
 -	so = sonewconn(lso, SS_ISCONNECTED);
 +	so = sonewconn(lso, 0);
  	if (so == NULL) {
  		/*
  		 * Drop the connection; we will either send a RST or
 @@ -922,6 +922,8 @@ syncache_socket(struct syncache *sc, str
  
  	INP_WUNLOCK(inp);
  
 +	soisconnected(so);
 +
  	TCPSTAT_INC(tcps_accepts);
  	return (so);
  
 
 Modified: head/sys/netinet/tcp_usrreq.c
 ==============================================================================
 --- head/sys/netinet/tcp_usrreq.c	Tue Jan 28 19:12:31 2014	(r261241)
 +++ head/sys/netinet/tcp_usrreq.c	Tue Jan 28 20:28:32 2014	(r261242)
 @@ -610,13 +610,6 @@ out:
  /*
   * Accept a connection.  Essentially all the work is done at higher levels;
   * just return the address of the peer, storing through addr.
 - *
 - * The rationale for acquiring the tcbinfo lock here is somewhat complicated,
 - * and is described in detail in the commit log entry for r175612.  Acquiring
 - * it delays an accept(2) racing with sonewconn(), which inserts the socket
 - * before the inpcb address/port fields are initialized.  A better fix would
 - * prevent the socket from being placed in the listen queue until all fields
 - * are fully initialized.
   */
  static int
  tcp_usr_accept(struct socket *so, struct sockaddr **nam)
 @@ -633,7 +626,6 @@ tcp_usr_accept(struct socket *so, struct
  
  	inp = sotoinpcb(so);
  	KASSERT(inp != NULL, ("tcp_usr_accept: inp == NULL"));
 -	INP_INFO_RLOCK(&V_tcbinfo);
  	INP_WLOCK(inp);
  	if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
  		error = ECONNABORTED;
 @@ -653,7 +645,6 @@ tcp_usr_accept(struct socket *so, struct
  out:
  	TCPDEBUG2(PRU_ACCEPT);
  	INP_WUNLOCK(inp);
 -	INP_INFO_RUNLOCK(&V_tcbinfo);
  	if (error == 0)
  		*nam = in_sockaddr(port, &addr);
  	return error;
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