Re: [PATCH 1/7] omap: iommu: migrate to the generic IOMMU API

From: "Roedel, Joerg" <Joerg.Roedel@amd.com>
To: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Tony Lindgren <tony@atomide.com>,
	Hiroshi DOYU <Hiroshi.DOYU@nokia.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/7] omap: iommu: migrate to the generic IOMMU API
Date: Wed, 24 Aug 2011 15:15:27 +0200	[thread overview]
Message-ID: <20110824131527.GI2079@amd.com> (raw)
In-Reply-To: <CAK=WgbZAMbPhDuXZ2NwTTSDv2doT6WBSzCCaD0F02mybNEZyeA@mail.gmail.com>

On Wed, Aug 24, 2011 at 08:46:13AM -0400, Ohad Ben-Cohen wrote:
> On Tue, Aug 23, 2011 at 5:59 PM, Ohad Ben-Cohen <ohad@wizery.com> wrote:
> > On Tue, Aug 23, 2011 at 5:07 PM, Roedel, Joerg <Joerg.Roedel@amd.com> wrote:
> >> Can this be easily converted to a spin_lock?
> >
> > Sure, thanks for reviewing.
> 
> Taking a second look, I don't think it's necessary - the mutex isn't
> used to protect the page table. The page table is protected by a spin
> lock, so map/unmap operations can be called from an atomic context.
> 
> The mutex is only part of the attach/deattach operations, which are
> already used today in process context, so I guess it's safe.

Yes, it should be safe in your context. But the iommu-api is generic and
I would prefer that all functions it provides can be called from any
context.
Or is the time required for attaching/detaching too long so that it
makes sense to put secondary threads to sleep?

	Joerg

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