[src/trunk]: src/sys/netinet Run tcp_slowtimo in workqueue if NET_MPSAFE

[ozaki-r <ozaki-r%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/7bd327e6e625
branches:  trunk
changeset: 829138:7bd327e6e625
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Fri Jan 19 07:53:01 2018 +0000

description:
Run tcp_slowtimo in workqueue if NET_MPSAFE

If NET_MPSAFE is enabled, we have to avoid taking softnet_lock in softint as
much as possible to prevent any softint handlers including callout handlers
such as tcp_slowtimo from sticking on softnet_lock because it results in
undesired delays of executing subsequent softint handlers.

NFCI for !NET_MPSAFE

diffstat:

 sys/netinet/tcp_subr.c  |   9 +++------
 sys/netinet/tcp_timer.c |  46 ++++++++++++++++++++++++++++++++++++++++++----
 sys/netinet/tcp_timer.h |   3 ++-
 sys/netinet/tcp_var.h   |   4 +---
 4 files changed, 48 insertions(+), 14 deletions(-)

diffs (171 lines):

diff -r cdf98bd85df5 -r 7bd327e6e625 sys/netinet/tcp_subr.c
--- a/sys/netinet/tcp_subr.c    Fri Jan 19 07:52:37 2018 +0000
+++ b/sys/netinet/tcp_subr.c    Fri Jan 19 07:53:01 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tcp_subr.c,v 1.271 2017/07/29 05:08:48 maxv Exp $      */
+/*     $NetBSD: tcp_subr.c,v 1.272 2018/01/19 07:53:01 ozaki-r Exp $   */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -91,7 +91,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tcp_subr.c,v 1.271 2017/07/29 05:08:48 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tcp_subr.c,v 1.272 2018/01/19 07:53:01 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -382,8 +382,6 @@
 struct mowner tcp_sock_tx_mowner = MOWNER_INIT("tcp", "sock tx");
 #endif
 
-callout_t tcp_slowtimo_ch;
-
 static int
 do_tcpinit(void)
 {
@@ -424,8 +422,7 @@
 
        vtw_earlyinit();
 
-       callout_init(&tcp_slowtimo_ch, CALLOUT_MPSAFE);
-       callout_reset(&tcp_slowtimo_ch, 1, tcp_slowtimo, NULL);
+       tcp_slowtimo_init();
 
        return 0;
 }
diff -r cdf98bd85df5 -r 7bd327e6e625 sys/netinet/tcp_timer.c
--- a/sys/netinet/tcp_timer.c   Fri Jan 19 07:52:37 2018 +0000
+++ b/sys/netinet/tcp_timer.c   Fri Jan 19 07:53:01 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tcp_timer.c,v 1.92 2017/07/28 19:16:41 maxv Exp $      */
+/*     $NetBSD: tcp_timer.c,v 1.93 2018/01/19 07:53:01 ozaki-r Exp $   */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -93,11 +93,12 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tcp_timer.c,v 1.92 2017/07/28 19:16:41 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tcp_timer.c,v 1.93 2018/01/19 07:53:01 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
 #include "opt_tcp_debug.h"
+#include "opt_net_mpsafe.h"
 #endif
 
 #include <sys/param.h>
@@ -108,6 +109,8 @@
 #include <sys/protosw.h>
 #include <sys/errno.h>
 #include <sys/kernel.h>
+#include <sys/callout.h>
+#include <sys/workqueue.h>
 
 #include <net/if.h>
 
@@ -149,6 +152,15 @@
 
 int    tcp_maxpersistidle = 0;         /* max idle time in persist */
 
+static callout_t       tcp_slowtimo_ch;
+#ifdef NET_MPSAFE
+static struct workqueue        *tcp_slowtimo_wq;
+static struct work     tcp_slowtimo_wk;
+#endif
+
+static void tcp_slowtimo_work(struct work *, void *);
+static void tcp_slowtimo(void *);
+
 /*
  * Time to delay the ACK.  This is initialized in tcp_init(), unless
  * its patched.
@@ -193,6 +205,21 @@
                tcp_delack_ticks = TCP_DELACK_TICKS;
 }
 
+void
+tcp_slowtimo_init(void)
+{
+#ifdef NET_MPSAFE
+       int error;
+
+       error = workqueue_create(&tcp_slowtimo_wq, "tcp_slowtimo",
+           tcp_slowtimo_work, NULL, PRI_SOFTNET, IPL_SOFTNET, WQ_MPSAFE);
+       if (error != 0)
+               panic("%s: workqueue_create failed (%d)\n", __func__, error);
+#endif
+       callout_init(&tcp_slowtimo_ch, CALLOUT_MPSAFE);
+       callout_reset(&tcp_slowtimo_ch, 1, tcp_slowtimo, NULL);
+}
+
 /*
  * Callout to process delayed ACKs for a TCPCB.
  */
@@ -229,8 +256,8 @@
  * Updates the timers in all active tcb's and
  * causes finite state machine actions if timers expire.
  */
-void
-tcp_slowtimo(void *arg)
+static void
+tcp_slowtimo_work(struct work *wk, void *arg)
 {
 
        mutex_enter(softnet_lock);
@@ -241,6 +268,17 @@
        callout_schedule(&tcp_slowtimo_ch, hz / PR_SLOWHZ);
 }
 
+static void
+tcp_slowtimo(void *arg)
+{
+
+#ifdef NET_MPSAFE
+       workqueue_enqueue(tcp_slowtimo_wq, &tcp_slowtimo_wk, NULL);
+#else
+       tcp_slowtimo_work(NULL, NULL);
+#endif
+}
+
 /*
  * Cancel all timers for TCP tp.
  */
diff -r cdf98bd85df5 -r 7bd327e6e625 sys/netinet/tcp_timer.h
--- a/sys/netinet/tcp_timer.h   Fri Jan 19 07:52:37 2018 +0000
+++ b/sys/netinet/tcp_timer.h   Fri Jan 19 07:53:01 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tcp_timer.h,v 1.28 2011/05/24 18:37:52 gdt Exp $       */
+/*     $NetBSD: tcp_timer.h,v 1.29 2018/01/19 07:53:01 ozaki-r Exp $   */
 
 /*-
  * Copyright (c) 2001, 2005 The NetBSD Foundation, Inc.
@@ -190,6 +190,7 @@
 extern const int tcp_backoff[];
 
 void   tcp_timer_init(void);
+void   tcp_slowtimo_init(void);
 #endif
 
 #endif /* !_NETINET_TCP_TIMER_H_ */
diff -r cdf98bd85df5 -r 7bd327e6e625 sys/netinet/tcp_var.h
--- a/sys/netinet/tcp_var.h     Fri Jan 19 07:52:37 2018 +0000
+++ b/sys/netinet/tcp_var.h     Fri Jan 19 07:53:01 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tcp_var.h,v 1.181 2017/11/15 09:55:22 ozaki-r Exp $    */
+/*     $NetBSD: tcp_var.h,v 1.182 2018/01/19 07:53:01 ozaki-r Exp $    */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -928,8 +928,6 @@
 int     tcp_signature_compute(struct mbuf *, struct tcphdr *, int, int,
            int, u_char *, u_int);
 #endif
-void    tcp_slowtimo(void *);
-extern callout_t tcp_slowtimo_ch;
 void    tcp_fasttimo(void);
 struct mbuf *
         tcp_template(struct tcpcb *);