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Date:      Sun, 01 Oct 2006 15:48:26 -0500
From:      Alan Cox <alc@cs.rice.edu>
To:        Martin Blapp <mb@imp.ch>
Cc:        alc@freebsd.org, current@freebsd.org
Subject:   Re: CURRENT unusable again, too many panics
Message-ID:  <4520299A.80102@cs.rice.edu>
In-Reply-To: <20061001223622.R91466@godot.imp.ch>
References:  <20060928195536.Y91466@godot.imp.ch> <20061001132422.O91466@godot.imp.ch> <45201C2B.7080706@cs.rice.edu> <20061001223622.R91466@godot.imp.ch>

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Martin Blapp wrote:

>> Can you tell me what if anything is printed with the attached patch 
>> applied?
>>
>
> Hi,
>
>>  MFC
>>    Correct a very old and very obscure bug: vmspace_fork() calls
>>    pmap_copy() if the mapping is VM_INHERIT_SHARE.  Suppose the mapping
>>    is also wired.  vmspace_fork() clears the wiring attributes in the vm
>>    map entry but pmap_copy() copies the PG_W attribute in the PTE.  I
>>    don't think this is catastrophic.  It blocks pmap_remove_pages() from
>>    destroying the mapping and corrupts the pmap's wiring count.
>
>
> With or without this MFC applied ?
>
It won't matter.  However, the patch will likely not apply cleanly with 
the above change backed out simply due to the context being different. 

Alan




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