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Date: Sat, 3 Nov 2001 13:01:56 -0800
From: Richard Henderson <rth@twiddle.net>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, Juergen Doelle <jdoelle@de.ibm.com>,
        linux-kernel@vger.kernel.org
Subject: Re: Pls apply this spinlock patch to the kernel
Message-ID: <20011103130156.D5984@twiddle.net>
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In-Reply-To: <Pine.LNX.4.33.0111031215490.2026-100000@penguin.transmeta.com>; from torvalds@transmeta.com on Sat, Nov 03, 2001 at 12:20:53PM -0800
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On Sat, Nov 03, 2001 at 12:20:53PM -0800, Linus Torvalds wrote:
> If you have a 4-byte entry that is aligned to 128 bytes, you have 124
> bytes of stuff that the linker _will_ fill up with other things.

If you put the alignment on the type, not the variable, e.g.

  typedef int aligned_int __attribute__((aligned(128)));
  aligned_int foo;

then sizeof(foo) == 128, and the linker sees a 128-byte object,
not a 4 byte object with 128 byte alignment.

It's a subtle difference between alignment of types and alignment
of variables, but it makes sense if you think about it.


r~
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