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Date:      Tue, 4 Nov 2008 17:07:25 -0500
From:      John Baldwin <jhb@freebsd.org>
To:        David Xu <davidxu@freebsd.org>
Cc:        svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org
Subject:   Re: svn commit: r184216 - head/sys/kern
Message-ID:  <200811041707.26052.jhb@freebsd.org>
In-Reply-To: <200810240103.m9O13V7f071075@svn.freebsd.org>
References:  <200810240103.m9O13V7f071075@svn.freebsd.org>

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On Thursday 23 October 2008 09:03:31 pm David Xu wrote:
> Author: davidxu
> Date: Fri Oct 24 01:03:31 2008
> New Revision: 184216
> URL: http://svn.freebsd.org/changeset/base/184216
> 
> Log:
>   partly revert revision 184199, because TDF_NEEDSIGCHK is persitent
>   when thread is in kernel mode, it can cause dead loop, now unlock
>   process lock after acquired sleep queue lock and thread lock to
>   avoid the problem. This means TDF_NEEDSIGCHK and TDF_NEEDSUSPCHK must
>   be set with process lock and thread lock being hold at same time.

You can't unlock the proc lock while holding the thread_lock().  This will 
lead to deadlock due to the way that thread_lock() works.  This is different 
from the rules in 6.x where you could drop a mutex while holding sched_lock.  
You will need to revert this.

-- 
John Baldwin



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