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Date: Tue, 24 Sep 2002 18:14:01 -0700
From: alfred@leakybucket.org
To: linux-kernel@vger.kernel.org
Subject: [patch] Re: 2 futex questions
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On Wed, Sep 25, 2002 at 10:23:16AM +0200, Ingo Molnar wrote:
> 
> what it says: 'uaddr must be naturally aligned, and the word must be on a
> single page'. In theory it's possible that __alignof__(int) !=
> sizeof(int).
> 

Ok, would the following actually save some cycles then?

diff -u a/kernel/futex.c b/kernel/futex.c 
--- a/kernel/futex.c    Tue Sep 24 15:25:01 2002
+++ b/kernel/futex.c    Tue Sep 24 18:09:09 2002
@@ -321,9 +321,10 @@
 
        pos_in_page = ((unsigned long)uaddr) % PAGE_SIZE;
 
-       /* Must be "naturally" aligned, and not on page boundary. */
+       /* Must be "naturally" aligned, and must not cross a page boundary. */
        if ((pos_in_page % __alignof__(int)) != 0
-           || pos_in_page + sizeof(int) > PAGE_SIZE)
+           || ((sizeof(int) != __alignof__(int))
+                && (pos_in_page + sizeof(int) > PAGE_SIZE)))
                return -EINVAL;
 
        /* Simpler if it doesn't vanish underneath us. */


Alfred Landrum