linux-kernel - Re: [Bug 7505] Linux-2.6.18 fails to boot on AMD64 machine

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Date:	Thu, 21 Dec 2006 12:11:50 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Ard -kwaak- van Breemen <ard@...egraafnet.nl>
Cc:	"Zhang, Yanmin" <yanmin.zhang@...el.com>,
	Chuck Ebbert <76306.1226@...puserve.com>,
	Yinghai Lu <yinghai.lu@....com>, take@...ero.it,
	agalanin@...a.ru, linux-kernel@...r.kernel.org,
	bugme-daemon@...zilla.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [Bug 7505] Linux-2.6.18 fails to boot on AMD64 machine

On Thu, 21 Dec 2006 20:52:40 +0100
Ard -kwaak- van Breemen <ard@...egraafnet.nl> wrote:

> Hello,
> 
> On Thu, Dec 21, 2006 at 04:04:04PM +0800, Zhang, Yanmin wrote:
> > I couldn't reproduce it on my EM64T machine. I instrumented function start_kernel and
> > didn't find irq was enabled before calling init_IRQ. It'll be better if the reporter could
> > instrument function start_kernel to capture which function enables irq.
> Just diving into the sources.
> Is that something like:
> if(!raw_irqs_disabled_flags) printk "irqs are enabled";
> 
> (At that moment it might have crashed already.. :-)).
> 
> I don't see the complete context yet, but I hope the irq is
> triggered after the irq is somehow enabled.
> 
> BTW: the panic occurs on half of my boards on tyan S2891 with 2
> opterons, of which the only difference seems to be the purchase
> date (and hence probably the motherboard revisions). (Haven't got
> time yet to pull them out of the rack and compare the
> motherboards).

please, I'm still waiting for someone to tell me whether this "fixes" it:


--- a/lib/rwsem-spinlock.c~down_write-preserve-local-irqs
+++ a/lib/rwsem-spinlock.c
@@ -195,13 +195,14 @@ void fastcall __sched __down_write_neste
 {
 	struct rwsem_waiter waiter;
 	struct task_struct *tsk;
+	unsigned long flags;
 
-	spin_lock_irq(&sem->wait_lock);
+	spin_lock_irqsave(&sem->wait_lock, flags);
 
 	if (sem->activity == 0 && list_empty(&sem->wait_list)) {
 		/* granted */
 		sem->activity = -1;
-		spin_unlock_irq(&sem->wait_lock);
+		spin_unlock_irqrestore(&sem->wait_lock, flags);
 		goto out;
 	}
 
@@ -216,7 +217,7 @@ void fastcall __sched __down_write_neste
 	list_add_tail(&waiter.list, &sem->wait_list);
 
 	/* we don't need to touch the semaphore struct anymore */
-	spin_unlock_irq(&sem->wait_lock);
+	spin_unlock_irqrestore(&sem->wait_lock, flags);
 
 	/* wait to be given the lock */
 	for (;;) {
_

-
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