TCP/UDP/etc input path w/o KERNEL_LOCK()

[Martin Pieuchot]

New year, new diff.  Assuming we can live with the kqueue(2) races,
here's a diff to remove the KERNEL_LOCK() from all pr_input() routines.

I'd appreciate tests.

Index: net/if.c
===================================================================
RCS file: /cvs/src/sys/net/if.c,v
retrieving revision 1.533
diff -u -p -r1.533 if.c
--- net/if.c    2 Jan 2018 12:52:17 -0000       1.533
+++ net/if.c    2 Jan 2018 14:32:05 -0000
@@ -926,7 +926,6 @@ if_netisr(void *unused)
 {
        int n, t = 0;
 
-       KERNEL_LOCK();
        NET_LOCK();
 
        while ((n = netisr) != 0) {
@@ -940,8 +939,11 @@ if_netisr(void *unused)
                atomic_clearbits_int(&netisr, n);
 
 #if NETHER > 0
-               if (n & (1 << NETISR_ARP))
+               if (n & (1 << NETISR_ARP)) {
+                       KERNEL_LOCK();
                        arpintr();
+                       KERNEL_UNLOCK();
+               }
 #endif
                if (n & (1 << NETISR_IP))
                        ipintr();
@@ -950,35 +952,52 @@ if_netisr(void *unused)
                        ip6intr();
 #endif
 #if NPPP > 0
-               if (n & (1 << NETISR_PPP))
+               if (n & (1 << NETISR_PPP)) {
+                       KERNEL_LOCK();
                        pppintr();
+                       KERNEL_UNLOCK();
+               }
 #endif
 #if NBRIDGE > 0
-               if (n & (1 << NETISR_BRIDGE))
+               if (n & (1 << NETISR_BRIDGE)) {
+                       KERNEL_LOCK();
                        bridgeintr();
+                       KERNEL_UNLOCK();
+               }
 #endif
 #if NSWITCH > 0
-               if (n & (1 << NETISR_SWITCH))
+               if (n & (1 << NETISR_SWITCH)) {
+                       KERNEL_LOCK();
                        switchintr();
+                       KERNEL_UNLOCK();
+               }
 #endif
 #if NPPPOE > 0
-               if (n & (1 << NETISR_PPPOE))
+               if (n & (1 << NETISR_PPPOE)) {
+                       KERNEL_LOCK();
                        pppoeintr();
+                       KERNEL_UNLOCK();
+               }
 #endif
 #ifdef PIPEX
-               if (n & (1 << NETISR_PIPEX))
+               if (n & (1 << NETISR_PIPEX)) {
+                       KERNEL_LOCK();
                        pipexintr();
+                       KERNEL_UNLOCK();
+               }
 #endif
                t |= n;
        }
 
 #if NPFSYNC > 0
-       if (t & (1 << NETISR_PFSYNC))
+       if (t & (1 << NETISR_PFSYNC)) {
+               KERNEL_LOCK();
                pfsyncintr();
+               KERNEL_UNLOCK();
+       }
 #endif
 
        NET_UNLOCK();
-       KERNEL_UNLOCK();
 }
 
 void