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Re: MIPS: Get rid of branches to .subsections.

To: "Maciej W. Rozycki" <macro@linux-mips.org>
Subject: Re: MIPS: Get rid of branches to .subsections.
From: Ralf Baechle <ralf@linux-mips.org>
Date: Mon, 23 Aug 2010 11:12:57 +0100
Cc: linux-mips@linux-mips.org, Paul Gortmaker <paul.gortmaker@windriver.com>
In-reply-to: <alpine.LFD.2.00.1008230139480.900@eddie.linux-mips.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20100818124310.GA23744@linux-mips.org> <alpine.LFD.2.00.1008230139480.900@eddie.linux-mips.org>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.20 (2009-12-10)
On Mon, Aug 23, 2010 at 01:54:24AM +0100, Maciej W. Rozycki wrote:

> > By rewriting the loop around all simple LL/SC blocks to C we reduce reduce
> > the amount of inline assembler and at the same time allow GCC to often
> > fill the branch delay slots with something sensible or whever else clever
> > optimization it may have up in its sleeve.
> 
>  Are you sure it won't reorder anything there that actually relies on the 
> atomic access to have succeeded?  I suggest adding barrier() after the 
> loop.

None of the things that were touched by the code had any barrier
functionality  Some of the functions such as atomic_add don't provide
memory barriers but where needed a barrier was always provided by C code
near the end of the function, for example in atomic_add_return.

  Ralf

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