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Date: Mon, 18 Nov 2002 15:09:42 -0800
From: Andrew Morton <akpm@digeo.com>
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To: Dave Hansen <haveblue@us.ibm.com>
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       mingo@elte.hu, rml@tech9.net, riel@surriel.com,
       Davide Libenzi <davidel@xmailserver.org>
Subject: Re: unusual scheduling performance
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Dave Hansen wrote:
> 
> As Andrew suggested, I put a dump_stack() in rwsem_down_write_failed().
> 
> This was actually in a 2.5.47 bk snapshot, so it has eventpoll in it.

So printk("hey!\n") would have worked.  Looks like it would have
talked to you, too...

> kksymoops is broken, so:
> dmesg | tail -20 | sort | uniq | ksymoops -m /boot/System.map
> 
> Trace; c01c5757 <rwsem_down_write_failed+27/170>
> Trace; c01220c6 <update_wall_time+16/50>
> Trace; c01223ee <do_timer+2e/c0>
> Trace; c0166bd3 <.text.lock.eventpoll+6/f3>
> Trace; c0146568 <__fput+18/c0>
> Trace; c010ae9a <handle_IRQ_event+2a/60>
> Trace; c0144a05 <filp_close+85/b0>
> Trace; c0144a8d <sys_close+5d/70>
> Trace; c0108fab <syscall_call+7/b>
> 

So it would appear that eventpoll_release() is the problem.
How odd.  You're not actually _using_ epoll there, are you?