linux-kernel - Re: avoiding duplicate icache flushing of shared maps on nommu

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Message-ID: <8bd0f97a0912021340l47b861a6l8444f8246581375@mail.gmail.com>
Date:	Wed, 2 Dec 2009 16:40:15 -0500
From:	Mike Frysinger <vapier.adi@...il.com>
To:	David Howells <dhowells@...hat.com>
Cc:	Paul Mundt <lethal@...ux-sh.org>,
	Bernd Schmidt <bernds_cb1@...nline.de>,
	Jie Zhang <jie.zhang@...log.com>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	uclinux-dist-devel <uclinux-dist-devel@...ckfin.uclinux.org>
Subject: Re: avoiding duplicate icache flushing of shared maps on nommu

On Wed, Dec 2, 2009 at 09:15, David Howells wrote:
> Mike Frysinger wrote:
>> (yes, this now does the icache flush while holding the
>> nommu_region_sem, but i'm interested if the _idea_ is OK)
>
> Yes...  But it's not quite as simple as you think.  The first mapping made of
> a file could be PROT_READ only, in which case a second, executable mapping
> made that shares it would not get flushed from the icache.

that is a tricky edge case ;)

> How about the attached patch?

it works, but i think we want to put the vm_icache_flushed in
linux/mm_types.h behind NOMMU so we dont bloat the MMU guys ?
-mike
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