[src/trunk]: src/sys/net Replace adaptive mutex for ethercom with spin one

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

details:   https://anonhg.NetBSD.org/src/rev/bd7f0db0edff
branches:  trunk
changeset: 820449:bd7f0db0edff
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Tue Jan 10 05:40:59 2017 +0000

description:
Replace adaptive mutex for ethercom with spin one

Unfortunately even wm(4) doesn't allow adaptive mutex because wm(4)
tries to hold it with holding its own spin mutex.

diffstat:

 sys/net/if_ethersubr.c |  63 +++++++++++++++++++++++++++++++++++--------------
 1 files changed, 45 insertions(+), 18 deletions(-)

diffs (114 lines):

diff -r cf4ae42fe982 -r bd7f0db0edff sys/net/if_ethersubr.c
--- a/sys/net/if_ethersubr.c    Tue Jan 10 05:08:24 2017 +0000
+++ b/sys/net/if_ethersubr.c    Tue Jan 10 05:40:59 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_ethersubr.c,v 1.232 2016/12/31 15:07:02 ozaki-r Exp $       */
+/*     $NetBSD: if_ethersubr.c,v 1.233 2017/01/10 05:40:59 ozaki-r Exp $       */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -61,7 +61,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_ethersubr.c,v 1.232 2016/12/31 15:07:02 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_ethersubr.c,v 1.233 2017/01/10 05:40:59 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -967,7 +967,7 @@
                if_set_sadl(ifp, lla, ETHER_ADDR_LEN, !ETHER_IS_LOCAL(lla));
 
        LIST_INIT(&ec->ec_multiaddrs);
-       ec->ec_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE);
+       ec->ec_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NET);
        ifp->if_broadcastaddr = etherbroadcastaddr;
        bpf_attach(ifp, DLT_EN10MB, sizeof(struct ether_header));
 #ifdef MBUFTRACE
@@ -1535,13 +1535,15 @@
 ether_multicast_sysctl(SYSCTLFN_ARGS)
 {
        struct ether_multi *enm;
-       struct ether_multi_sysctl addr;
        struct ifnet *ifp;
        struct ethercom *ec;
        int error = 0;
        size_t written;
        struct psref psref;
        int bound, s;
+       unsigned int multicnt;
+       struct ether_multi_sysctl *addrs;
+       int i;
 
        if (namelen != 1)
                return EINVAL;
@@ -1561,30 +1563,55 @@
 
        if (oldp == NULL) {
                if_put(ifp, &psref);
-               *oldlenp = ec->ec_multicnt * sizeof(addr);
+               *oldlenp = ec->ec_multicnt * sizeof(*addrs);
                goto out;
        }
 
-       memset(&addr, 0, sizeof(addr));
-       error = 0;
-       written = 0;
+       /*
+        * ec->ec_lock is a spin mutex so we cannot call sysctl_copyout, which
+        * is sleepable, with holding it. Copy data to a local buffer first
+        * with holding it and then call sysctl_copyout without holding it.
+        */
+retry:
+       multicnt = ec->ec_multicnt;
+       addrs = kmem_alloc(sizeof(*addrs) * multicnt, KM_SLEEP);
 
        s = splnet();
        mutex_enter(ec->ec_lock);
+       if (multicnt < ec->ec_multicnt) {
+               /* The number of multicast addresses have increased */
+               mutex_exit(ec->ec_lock);
+               splx(s);
+               kmem_free(addrs, sizeof(*addrs) * multicnt);
+               goto retry;
+       }
+
+       i = 0;
        LIST_FOREACH(enm, &ec->ec_multiaddrs, enm_list) {
-               if (written + sizeof(addr) > *oldlenp)
-                       break;
-               addr.enm_refcount = enm->enm_refcount;
-               memcpy(addr.enm_addrlo, enm->enm_addrlo, ETHER_ADDR_LEN);
-               memcpy(addr.enm_addrhi, enm->enm_addrhi, ETHER_ADDR_LEN);
-               error = sysctl_copyout(l, &addr, oldp, sizeof(addr));
-               if (error)
-                       break;
-               written += sizeof(addr);
-               oldp = (char *)oldp + sizeof(addr);
+               struct ether_multi_sysctl *addr = &addrs[i];
+               addr->enm_refcount = enm->enm_refcount;
+               memcpy(addr->enm_addrlo, enm->enm_addrlo, ETHER_ADDR_LEN);
+               memcpy(addr->enm_addrhi, enm->enm_addrhi, ETHER_ADDR_LEN);
+               i++;
        }
        mutex_exit(ec->ec_lock);
        splx(s);
+
+       error = 0;
+       written = 0;
+       for (i = 0; i < multicnt; i++) {
+               struct ether_multi_sysctl *addr = &addrs[i];
+
+               if (written + sizeof(*addr) > *oldlenp)
+                       break;
+               error = sysctl_copyout(l, addr, oldp, sizeof(*addr));
+               if (error)
+                       break;
+               written += sizeof(*addr);
+               oldp = (char *)oldp + sizeof(*addr);
+       }
+       kmem_free(addrs, sizeof(*addrs) * multicnt);
+
        if_put(ifp, &psref);
 
        *oldlenp = written;