Subject: Re: map user memory in kernel
To: Steven M. Bellovin <>
From: Eric Haszlakiewicz <>
List: tech-kern
Date: 11/05/2005 10:45:52
On Sat, Nov 05, 2005 at 11:15:16AM -0500, Steven M. Bellovin wrote:
> Unless I badly misunderstand the situation, it doesn't matter.  The 
> "address" is nothing of the sort.  Think of it as a hash value; any 
> process that is sleeping on that hash value will be awakened, but they 
> should all check to see that the situation they're really waiting for 
> has occurred.  Otherwise, they sleep again.  
> To put it more bluntly: the system would still work correctly if every 
> process used 0 as its sleep "address".  It wouldn't be very efficient, 
> which is why things aren't done that way, but it would still be correct.

	It _does_ matter if you're using the physical address as the key
to pass to sleep/wakeup.  It wouldn't work correctly if the page got
paged back in to a different physical address.  Then you've called sleep
with one value and might call wakeup with a different one.