is_sk locking in sk_attach

[Bjoern A. Zeeb]

Hi,

there had been some discussion lately about if_sk and attach locking.
compiled if_sk as module on amd64 and kldloading started a race with
follwoing output:

--- very short part of console log ---
[some hundred more of the following lines]
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
malloc(M_WAITOK) of "64", forcing M_NOWAIT with the following non-sleepable locks held:
exclusive sleep mutex skc0 (network driver) r = 0 (0xffffff003000b670) locked @ /u1/src/HEAD/src/sys/pci/if_sk.c:1335
Stack backtrace:
witness_warn() at witness_warn+0x1a7
uma_zalloc_arg() at uma_zalloc_arg+0x4c
malloc() at malloc+0x9f
scope6_ifattach() at scope6_ifattach+0x20
in6_domifattach() at in6_domifattach+0x91
if_attachdomain1() at if_attachdomain1+0xb9
if_attach() at if_attach+0x465
ether_ifattach() at ether_ifattach+0x27
sk_attach() at sk_attach+0x334
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
(null)() at 0
[some hundred more of these lines]
--- end ---



I solved this problem without further investigation of possible
bad impacts with this patch:


Index: if_sk.c
===================================================================
RCS file: /u2/src/CVS/prefixes/src/sys/pci/if_sk.c,v
retrieving revision 1.83
diff -u -p -r1.83 if_sk.c
--- if_sk.c	28 Jun 2004 20:07:03 -0000	1.83
+++ if_sk.c	10 Jul 2004 21:44:53 -0000
@@ -1332,7 +1332,9 @@ sk_attach(dev)
 	error = 0;
 	sc_if = device_get_softc(dev);
 	sc = device_get_softc(device_get_parent(dev));
+#if 0
 	SK_LOCK(sc);
+#endif
 	port = *(int *)device_get_ivars(dev);
 	free(device_get_ivars(dev), M_DEVBUF);
 	device_set_ivars(dev, NULL);
@@ -1472,7 +1474,9 @@ sk_attach(dev)
 	}

 fail:
+#if 0
 	SK_UNLOCK(sc);
+#endif
 	if (error) {
 		/* Access should be ok even though lock has been dropped */
 		sc->sk_if[port] = NULL;
--- end ---


can someone with some more knowledge about this driver and
general locking of if_* please review this. TIA.

-- 
Bjoern A. Zeeb				bzeeb at Zabbadoz dot NeT