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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: joerg.roedel@amd.com, dwmw2@infradead.org,
	iommu@lists.linux-foundation.org, bhelgaas@google.com,
	aik@ozlabs.ru, david@gibson.dropbear.id.au,
	konrad.wilk@oracle.com, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org, gregkh@linuxfoundation.org,
	ddutile@redhat.com, liuj97@gmail.com
Subject: Re: [PATCH v2 2/7] iommu: IOMMU Groups
Date: Thu, 21 Jun 2012 10:07:34 +1000	[thread overview]
Message-ID: <1340237254.28143.201.camel@pasglop> (raw)
In-Reply-To: <1340210921.5076.76.camel@bling.home>

On Wed, 2012-06-20 at 10:48 -0600, Alex Williamson wrote:

> Yes, I was assuming the caller held a reference to the struct device to
> prevent such a race, looks like I forgot to document that in the
> comments.  I'll have to think about if we can fix the ordering problem.
> We can re-order the list_add vs notification, but then we just risk
> dropping the remove.  Perhaps we need to extend the lock or add another
> to group {list add, notify add}, {list lookup, remove, notify remove}.
> I'm not even sure this race is possible though w/ a device reference.

Or we put the burden on the callers not to racily add & remove,
including full completion of related notifiers. Might not even be hard
(ie might already be the case).

Cheers,
Ben.



  reply	other threads:[~2012-06-21  0:07 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-30 20:18 [PATCH v2 0/7] IOMMU: Groups support Alex Williamson
2012-05-30 20:18 ` [PATCH v2 1/7] driver core: Add iommu_group tracking to struct device Alex Williamson
2012-06-20  5:45   ` Benjamin Herrenschmidt
2012-05-30 20:18 ` [PATCH v2 2/7] iommu: IOMMU Groups Alex Williamson
2012-06-20 10:01   ` Benjamin Herrenschmidt
2012-06-20 16:48     ` Alex Williamson
2012-06-21  0:07       ` Benjamin Herrenschmidt [this message]
2012-05-30 20:19 ` [PATCH v2 3/7] amd_iommu: Support IOMMU groups Alex Williamson
2012-05-30 20:19 ` [PATCH v2 4/7] intel-iommu: " Alex Williamson
2012-05-30 20:19 ` [PATCH v2 5/7] amd_iommu: Make use of DMA quirks and ACS checks in " Alex Williamson
2012-05-30 20:19 ` [PATCH v2 6/7] intel-iommu: " Alex Williamson
2012-05-31 19:47   ` Don Dutile
2012-05-31 20:41     ` Alex Williamson
2012-05-30 20:19 ` [PATCH v2 7/7] iommu: Remove group_mf Alex Williamson
2012-06-06 11:05 ` [PATCH v2 0/7] IOMMU: Groups support Joerg Roedel
2012-06-11 15:37   ` Alex Williamson
2012-06-12  2:55     ` Bjorn Helgaas
2012-06-18 17:31     ` Alex Williamson
2012-06-19  9:49       ` Joerg Roedel
2012-06-19 10:40         ` Benjamin Herrenschmidt
2012-06-25 11:29 ` Joerg Roedel

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