Subject: Re: 2.6.10-mm1 hang
From: Badari Pulavarty <pbadari@us.ibm.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
In-Reply-To: <20050119133136.7a1c0454.akpm@osdl.org>
References: <1106153215.3577.134.camel@dyn318077bld.beaverton.ibm.com>
	 <20050119133136.7a1c0454.akpm@osdl.org>
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Date: 20 Jan 2005 07:26:54 -0800
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I see different behaviours on different architectures.

	i386 - machine hang
	Power5 ppc64 - only the process hang
	Power3 ppc64 - machine hang

I modified it to use spin_lock() instead of spin_lock_irq()  -
things are the way I was expecting. Only process hang, not
the system. 

You may be right on other CPUs stuck on IPI.

Thanks,
Badari

On Wed, 2005-01-19 at 13:31, Andrew Morton wrote:
> Badari Pulavarty <pbadari@us.ibm.com> wrote:
> >
> > I was playing with kexec+kdump and ran into this on 2.6.10-mm1.
> >  I have seen similar behaviour on 2.6.10. 
> > 
> >  I am using a 4-way P-III machine. I have a module which tries
> >  gets same spinlock twice. When I try to "insmod" this module,
> >  my system hangs. All my windows froze, no more new logins,
> >  console froze, doesn't respond to sysrq. I wasn't expecting
> >  a system hang. Why ? Ideas ?
> > 
> 
> Maybe all the other CPUs are stuck trying to send an IPI to this one?  An
> NMI watchdog trace would tell.
> 
> >  #include <linux/init.h>
> >  #include <asm/uaccess.h>
> >  #include <linux/spinlock.h>
> >  spinlock_t mylock = SPIN_LOCK_UNLOCKED;
> >  static int __init panic_init(void)
> >  {
> >          spin_lock_irq(&mylock);
> >          spin_lock_irq(&mylock);
> >         return 1;
> >  }
> 

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