From: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
To: Alex Williamson
<alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: aik-sLpHqDYs0B2HXe+LvDLADg@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org,
linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
liuj97-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org,
david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org
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-xdHQ/5r00wBBDLzU/O5InQ@public.gmane.org>
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.
WARNING: multiple messages have this Message-ID (diff)
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.
next prev parent reply other threads:[~2012-06-21 0:07 UTC|newest]
Thread overview: 41+ 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 ` Alex Williamson
[not found] ` <20120530201424.31527.33142.stgit-xdHQ/5r00wBBDLzU/O5InQ@public.gmane.org>
2012-05-30 20:18 ` [PATCH v2 1/7] driver core: Add iommu_group tracking to struct device Alex Williamson
2012-05-30 20:18 ` Alex Williamson
[not found] ` <20120530201840.31527.47813.stgit-xdHQ/5r00wBBDLzU/O5InQ@public.gmane.org>
2012-06-20 5:45 ` Benjamin Herrenschmidt
2012-06-20 5:45 ` Benjamin Herrenschmidt
2012-05-30 20:18 ` [PATCH v2 2/7] iommu: IOMMU Groups Alex Williamson
2012-05-30 20:18 ` Alex Williamson
[not found] ` <20120530201852.31527.23265.stgit-xdHQ/5r00wBBDLzU/O5InQ@public.gmane.org>
2012-06-20 10:01 ` Benjamin Herrenschmidt
2012-06-20 10:01 ` Benjamin Herrenschmidt
2012-06-20 16:48 ` Alex Williamson
2012-06-20 16:48 ` Alex Williamson
[not found] ` <1340210921.5076.76.camel-xdHQ/5r00wBBDLzU/O5InQ@public.gmane.org>
2012-06-21 0:07 ` Benjamin Herrenschmidt [this message]
2012-06-21 0:07 ` Benjamin Herrenschmidt
2012-05-30 20:19 ` [PATCH v2 3/7] amd_iommu: Support IOMMU groups Alex Williamson
2012-05-30 20:19 ` Alex Williamson
2012-05-30 20:19 ` [PATCH v2 4/7] intel-iommu: " Alex Williamson
2012-05-30 20:19 ` 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 ` Alex Williamson
2012-05-30 20:19 ` [PATCH v2 6/7] intel-iommu: " Alex Williamson
2012-05-30 20:19 ` Alex Williamson
[not found] ` <20120530201942.31527.51604.stgit-xdHQ/5r00wBBDLzU/O5InQ@public.gmane.org>
2012-05-31 19:47 ` Don Dutile
2012-05-31 19:47 ` Don Dutile
[not found] ` <4FC7CAE5.7020306-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2012-05-31 20:41 ` Alex Williamson
2012-05-31 20:41 ` Alex Williamson
2012-05-30 20:19 ` [PATCH v2 7/7] iommu: Remove group_mf Alex Williamson
2012-05-30 20:19 ` Alex Williamson
2012-06-06 11:05 ` [PATCH v2 0/7] IOMMU: Groups support Joerg Roedel
2012-06-06 11:05 ` Joerg Roedel
[not found] ` <20120606110514.GG757-5C7GfCeVMHo@public.gmane.org>
2012-06-11 15:37 ` Alex Williamson
2012-06-11 15:37 ` Alex Williamson
2012-06-12 2:55 ` Bjorn Helgaas
[not found] ` <1339429021.24037.8.camel-xdHQ/5r00wBBDLzU/O5InQ@public.gmane.org>
2012-06-18 17:31 ` Alex Williamson
2012-06-18 17:31 ` Alex Williamson
2012-06-19 9:49 ` Joerg Roedel
2012-06-19 9:49 ` Joerg Roedel
[not found] ` <20120619094918.GH2624-5C7GfCeVMHo@public.gmane.org>
2012-06-19 10:40 ` Benjamin Herrenschmidt
2012-06-19 10:40 ` Benjamin Herrenschmidt
2012-06-25 11:29 ` Joerg Roedel
2012-06-25 11:29 ` Joerg Roedel
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