linux-kernel - Re: Mysterious RTC hangs on x86_64

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Message-ID: <46391716.9040001@redhat.com>
Date:	Wed, 02 May 2007 18:56:22 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Zachary Amsden <zach@...are.com>
CC:	Marcos Pinto <markybob@...il.com>, Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alessandro Zummo <a.zummo@...ertech.it>
Subject: Re: Mysterious RTC hangs on x86_64 - fixed, sort of

Zachary Amsden wrote:
> With this patch, /sbin/hwclock no longer hangs my AMD64 machine when run
> after reaching multiuser.  What I don't understand is why.  I have the
> RTC based sound sequencer timer as a module, but not loaded, and the
> error message I added to indicate broken rtc control does not fire.
> 
> So why is it that if I stop taking the rtc_task_lock and issuing the
> callbacks which should never be held or exist that my system no longer
> hard freezes?
> 
> --- /tmp/a      2007-05-03 15:36:07.451256181 -0700
> +++ drivers/char/rtc.c  2007-05-03 15:27:49.000000000 -0700
> @@ -265,10 +265,10 @@
>         spin_unlock (&rtc_lock);
>  
>         /* Now do the rest of the actions */
> -       spin_lock(&rtc_task_lock);
> -       if (rtc_callback)
> -               rtc_callback->func(rtc_callback->private_data);
> -       spin_unlock(&rtc_task_lock);
> +/*     spin_lock(&rtc_task_lock); */
> +//     if (rtc_callback)
> +//             rtc_callback->func(rtc_callback->private_data);
> +/*     spin_unlock(&rtc_task_lock); */
>         wake_up_interruptible(&rtc_wait);       

Try leaving the spinlocks and just disabling the callbacks. And maybe
enable spinlock debugging...

> 
> CONFIG_HPET_EMULATE_RTC=y

Did you try without that?

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