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Date:      Mon, 06 Feb 1995 21:06:58 -0800
From:      David Greenman <davidg@Root.COM>
To:        terry@cs.weber.edu (Terry Lambert)
Cc:        jmb@kryten.atinc.com, hackers@FreeBSD.org
Subject:   Re: MIT SHM X11 extensions? (fwd) 
Message-ID:  <199502070506.VAA00830@corbin.Root.COM>
In-Reply-To: Your message of "Mon, 06 Feb 95 21:04:23 MST." <9502070404.AA10165@cs.weber.edu> 

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>>    To protect executing, pageable, binaries from being clobbered...which is
>> exactly how it is used. The kernel is not a pageable binary, is not "executed"
>> in the traditional sense.
>
>See the first set of quoted material above -- how are you not tagging the
>vnode, yet you know to return ETXTBUSY?
>
>The only locking I can see is advisory.  And it *looks* like the VTEXT *is*
>being used.

   Sure it is, in the kernel for normal files that the kernel execs.

>How does this jive with it being OK to clobber your binary?

   It doesn't. I never said it did in the general case. My reply was about
Jonathan saying that you must use 'mv' to install a new kernel - that 'cp'ing
a new kernel would cause the system to crash. You then made the assertion that
'cp' can't be used because of the ETXTBUSY error. I said (more or less) that
this is simply not true for the kernel binary.

>Or did you think I was talking about the VTEXT flag being set on the kernel
>vnode?

   How could I have thought any different??? That **was** what we were talking
about.

>  I *know* that doesn't happen: the kernel isn't opened through the
>VFS, it's opened by the boot code.
>
>Is there something here I am missing?

   I guess so.

-DG



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