linux-kernel - Re: Fw: [PATCH] ia64: race flushing icache in do_no

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Message-ID: <Pine.LNX.4.64.0704280620150.9554@blonde.wat.veritas.com>
Date:	Sat, 28 Apr 2007 06:34:26 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Rohit Seth <rohitseth@...gle.com>
cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Mike Stroyan <mike.stroyan@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Luck, Tony" <tony.luck@...el.com>, linux-ia64@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Fw: [PATCH] ia64: race flushing icache in do_no_page path

On Fri, 27 Apr 2007, Rohit Seth wrote:
> On Fri, 2007-04-27 at 15:18 +0100, Hugh Dickins wrote:
> 
> Right.  Extra flush_icache_page routines will add cost to archs that
> have non-null definition of this routine.  BTW, isn't flush_icache_page
> marked for deprecation?

Yes, flush_icache_page is marked for deprecation: but that's hardly
a reason to add another under a different name!  (Not quite what you
did, but...)

> lazy_mmu_prot_update was added specifically for notifying change in
> protection.  So, in a way it is closer to update_mmu_cache (Which is for
> change in mappings itself).  Though for ia64 implementation, this ends
> up flushing the icaches when needed.

The ia64 implementation is the only one which has any use for it, and
it's only interested when it's executable i.e. "lazy_mmu_prot_update"
is a name concealing some overdesign.

> Hopefully my reply is useful.

Yes, thanks Rohit, and I'll want to read through it again later.
In particular, I've now a better idea what's "lazy" about it.

Hugh
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