[src/trunk]: src/sys Simplify by using atomic_swap instead of mutex

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

details:   https://anonhg.NetBSD.org/src/rev/a61348f79d9f
branches:  trunk
changeset: 346660:a61348f79d9f
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Tue Jul 26 05:53:30 2016 +0000

description:
Simplify by using atomic_swap instead of mutex

Suggested by kefren@

diffstat:

 sys/netinet/ip_flow.c   |  18 ++++++++----------
 sys/netinet6/ip6_flow.c |  18 ++++++++----------
 2 files changed, 16 insertions(+), 20 deletions(-)

diffs (135 lines):

diff -r b87f28c8aa5d -r a61348f79d9f sys/netinet/ip_flow.c
--- a/sys/netinet/ip_flow.c     Tue Jul 26 05:52:55 2016 +0000
+++ b/sys/netinet/ip_flow.c     Tue Jul 26 05:53:30 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ip_flow.c,v 1.73 2016/07/11 07:37:00 ozaki-r Exp $     */
+/*     $NetBSD: ip_flow.c,v 1.74 2016/07/26 05:53:30 ozaki-r Exp $     */
 
 /*-
  * Copyright (c) 1998 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ip_flow.c,v 1.73 2016/07/11 07:37:00 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ip_flow.c,v 1.74 2016/07/26 05:53:30 ozaki-r Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -46,6 +46,7 @@
 #include <sys/pool.h>
 #include <sys/sysctl.h>
 #include <sys/workqueue.h>
+#include <sys/atomic.h>
 
 #include <net/if.h>
 #include <net/if_dl.h>
@@ -430,7 +431,7 @@
        return NULL;
 }
 
-static bool ipflow_work_enqueued = false;
+static unsigned int ipflow_work_enqueued = 0;
 
 static void
 ipflow_slowtimo_work(struct work *wk, void *arg)
@@ -439,6 +440,9 @@
        struct ipflow *ipf, *next_ipf;
        uint64_t *ips;
 
+       /* We can allow enqueuing another work at this point */
+       atomic_swap_uint(&ipflow_work_enqueued, 0);
+
        mutex_enter(softnet_lock);
        mutex_enter(&ipflow_lock);
        KERNEL_LOCK(1, NULL);
@@ -458,7 +462,6 @@
                        ipf->ipf_uses = 0;
                }
        }
-       ipflow_work_enqueued = false;
        KERNEL_UNLOCK_ONE(NULL);
        mutex_exit(&ipflow_lock);
        mutex_exit(softnet_lock);
@@ -469,13 +472,8 @@
 {
 
        /* Avoid enqueuing another work when one is already enqueued */
-       mutex_enter(&ipflow_lock);
-       if (ipflow_work_enqueued) {
-               mutex_exit(&ipflow_lock);
+       if (atomic_swap_uint(&ipflow_work_enqueued, 1) == 1)
                return;
-       }
-       ipflow_work_enqueued = true;
-       mutex_exit(&ipflow_lock);
 
        workqueue_enqueue(ipflow_slowtimo_wq, &ipflow_slowtimo_wk, NULL);
 }
diff -r b87f28c8aa5d -r a61348f79d9f sys/netinet6/ip6_flow.c
--- a/sys/netinet6/ip6_flow.c   Tue Jul 26 05:52:55 2016 +0000
+++ b/sys/netinet6/ip6_flow.c   Tue Jul 26 05:53:30 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ip6_flow.c,v 1.28 2016/07/11 07:37:00 ozaki-r Exp $    */
+/*     $NetBSD: ip6_flow.c,v 1.29 2016/07/26 05:53:30 ozaki-r Exp $    */
 
 /*-
  * Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -38,7 +38,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ip6_flow.c,v 1.28 2016/07/11 07:37:00 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ip6_flow.c,v 1.29 2016/07/26 05:53:30 ozaki-r Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -53,6 +53,7 @@
 #include <sys/pool.h>
 #include <sys/sysctl.h>
 #include <sys/workqueue.h>
+#include <sys/atomic.h>
 
 #include <net/if.h>
 #include <net/if_dl.h>
@@ -466,13 +467,16 @@
        return ip6f;
 }
 
-static bool ip6flow_work_enqueued = false;
+static unsigned int ip6flow_work_enqueued = 0;
 
 void
 ip6flow_slowtimo_work(struct work *wk, void *arg)
 {
        struct ip6flow *ip6f, *next_ip6f;
 
+       /* We can allow enqueuing another work at this point */
+       atomic_swap_uint(&ip6flow_work_enqueued, 0);
+
        mutex_enter(softnet_lock);
        mutex_enter(&ip6flow_lock);
        KERNEL_LOCK(1, NULL);
@@ -490,7 +494,6 @@
                        ip6f->ip6f_forwarded = 0;
                }
        }
-       ip6flow_work_enqueued = false;
 
        KERNEL_UNLOCK_ONE(NULL);
        mutex_exit(&ip6flow_lock);
@@ -502,13 +505,8 @@
 {
 
        /* Avoid enqueuing another work when one is already enqueued */
-       mutex_enter(&ip6flow_lock);
-       if (ip6flow_work_enqueued) {
-               mutex_exit(&ip6flow_lock);
+       if (atomic_swap_uint(&ip6flow_work_enqueued, 1) == 1)
                return;
-       }
-       ip6flow_work_enqueued = true;
-       mutex_exit(&ip6flow_lock);
 
        workqueue_enqueue(ip6flow_slowtimo_wq, &ip6flow_slowtimo_wk, NULL);
 }