splnet() in socket layer

[Martin Pieuchot]

splnet() was necessary when link state changes were executed from
hardware interrupt handlers.  In 2013 they got deferred to their own
task, so KERNEL_LOCK() is what really protect these data structures.

This is part of my bigger socket lock diff.

ok?

Index: kern/uipc_socket.c
===================================================================
RCS file: /cvs/src/sys/kern/uipc_socket.c,v
retrieving revision 1.163
diff -u -p -r1.163 uipc_socket.c
--- kern/uipc_socket.c  6 Oct 2016 19:09:08 -0000       1.163
+++ kern/uipc_socket.c  7 Nov 2016 08:52:42 -0000
@@ -1037,12 +1037,10 @@ sorflush(struct socket *so)
 {
        struct sockbuf *sb = &so->so_rcv;
        struct protosw *pr = so->so_proto;
-       int s;
        struct sockbuf asb;
 
        sb->sb_flags |= SB_NOINTR;
        (void) sblock(sb, M_WAITOK);
-       s = splnet();
        socantrcvmore(so);
        sbunlock(sb);
        asb = *sb;
@@ -1052,7 +1050,6 @@ sorflush(struct socket *so)
                sb->sb_sel.si_note = asb.sb_sel.si_note;
                sb->sb_flags = SB_KNOTE;
        }
-       splx(s);
        if (pr->pr_flags & PR_RIGHTS && pr->pr_domain->dom_dispose)
                (*pr->pr_domain->dom_dispose)(asb.sb_mb);
        sbrelease(&asb);
@@ -1876,7 +1873,8 @@ soo_kqfilter(struct file *fp, struct kno
 {
        struct socket *so = kn->kn_fp->f_data;
        struct sockbuf *sb;
-       int s;
+
+       KERNEL_ASSERT_LOCKED();
 
        switch (kn->kn_filter) {
        case EVFILT_READ:
@@ -1894,10 +1892,9 @@ soo_kqfilter(struct file *fp, struct kno
                return (EINVAL);
        }
 
-       s = splnet();
        SLIST_INSERT_HEAD(&sb->sb_sel.si_note, kn, kn_selnext);
        sb->sb_flags |= SB_KNOTE;
-       splx(s);
+
        return (0);
 }
 
@@ -1905,12 +1902,12 @@ void
 filt_sordetach(struct knote *kn)
 {
        struct socket *so = kn->kn_fp->f_data;
-       int s = splnet();
+
+       KERNEL_ASSERT_LOCKED();
 
        SLIST_REMOVE(&so->so_rcv.sb_sel.si_note, kn, knote, kn_selnext);
        if (SLIST_EMPTY(&so->so_rcv.sb_sel.si_note))
                so->so_rcv.sb_flags &= ~SB_KNOTE;
-       splx(s);
 }
 
 int
@@ -1939,12 +1936,12 @@ void
 filt_sowdetach(struct knote *kn)
 {
        struct socket *so = kn->kn_fp->f_data;
-       int s = splnet();
+
+       KERNEL_ASSERT_LOCKED();
 
        SLIST_REMOVE(&so->so_snd.sb_sel.si_note, kn, knote, kn_selnext);
        if (SLIST_EMPTY(&so->so_snd.sb_sel.si_note))
                so->so_snd.sb_flags &= ~SB_KNOTE;
-       splx(s);
 }
 
 int