fix/workaround for usb probe lockups on nForce2 mbs

[Ian Dowse]

In message <3F73B467.5080500 at terrandev.com>, Brandon Fosdick writes:
>Ian Dowse wrote:
>> Great, thanks for tracking it down! It sounds very similar to a
>> problem people were having before with FAST_IPSEC where interrupts
>> were being enabled and confusing the USB code. You have a "uhci"
>> rather than an "ohci" controller I assume? If so, coould you try
>> the following patch instead? Unfortunately I don't have anything
>> to test this on, but it in theory it should work around this class
>> of problems by backporting from -CURRENT some logic for avoiding
>> interrupts in polling mode.
>
>My A7N8X-Deluxe has an ohci, not a uhci. I haven't tried either patch 
>yet, but I will in a minute.
>

In that case it won't help, sorry. I guess that means it is unlikely
to help on uhci controllers either. The hang is probably an interrupt
storm, not the driver getting stuck in a loop.

So the more important question is what could be lowering the cpl
priority during boot, allowing interrupts to be delivered? If someone
has the time to experiment, I'd like to see what happens if you
change sys/kern/subr_bus.c to add the following line just before
the `return error;' in device_probe_and_attach():

	device_printf(dev, "error %d, cpl %08x\n", error, cpl);

Actually, here's one more idea. Try the following patch on its own
to see if the hangs go away. It looks like kthread_create can
accidentally lower the cpl via fork1().

Ian

Index: kern_fork.c
===================================================================
RCS file: /home/iedowse/CVS/src/sys/kern/kern_fork.c,v
retrieving revision 1.72.2.14
diff -u -r1.72.2.14 kern_fork.c
--- kern_fork.c	26 Jun 2003 04:15:10 -0000	1.72.2.14
+++ kern_fork.c	26 Sep 2003 08:26:31 -0000
@@ -183,7 +183,7 @@
 	struct proc *p2, *pptr;
 	uid_t uid;
 	struct proc *newproc;
-	int ok;
+	int ok, s;
 	static int curfail = 0, pidchecked = 0;
 	static struct timeval lastfail;
 	struct forklist *ep;
@@ -544,10 +544,10 @@
 	 */
 	microtime(&(p2->p_stats->p_start));
 	p2->p_acflag = AFORK;
-	(void) splhigh();
+	s = splhigh();
 	p2->p_stat = SRUN;
 	setrunqueue(p2);
-	(void) spl0();
+	splx(s);
 
 	/*
 	 * Now can be swapped.