From: Jason Gunthorpe <jgg@nvidia.com>
To: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Matthew Rosato <mjrosato@linux.ibm.com>,
iommu@lists.linux.dev, Joerg Roedel <joro@8bytes.org>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Gerd Bayer <gbayer@linux.ibm.com>,
Pierre Morel <pmorel@linux.ibm.com>,
linux-s390@vger.kernel.org, borntraeger@linux.ibm.com,
hca@linux.ibm.com, gor@linux.ibm.com,
gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com,
svens@linux.ibm.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/5] iommu/s390: Use RCU to allow concurrent domain_list iteration
Date: Fri, 21 Oct 2022 10:36:31 -0300 [thread overview]
Message-ID: <Y1KgX8EwH8T+FgWC@nvidia.com> (raw)
In-Reply-To: <68d91d7a5aadbd46dc34470eccd6b86a84c9e47b.camel@linux.ibm.com>
On Fri, Oct 21, 2022 at 02:08:02PM +0200, Niklas Schnelle wrote:
> On Thu, 2022-10-20 at 08:05 -0300, Jason Gunthorpe wrote:
> > On Thu, Oct 20, 2022 at 10:51:10AM +0200, Niklas Schnelle wrote:
> >
> > > Ok that makes sense thanks for the explanation. So yes my assessment is
> > > still that in this situation the IOTLB flush is architected to return
> > > an error that we can ignore. Not the most elegant I admit but at least
> > > it's simple. Alternatively I guess we could use call_rcu() to do the
> > > zpci_unregister_ioat() but I'm not sure how to then make sure that a
> > > subsequent zpci_register_ioat() only happens after that without adding
> > > too much more logic.
> >
> > This won't work either as the domain could have been freed before the
> > call_rcu() happens, the domain needs to be detached synchronously
> >
> > Jason
>
> Yeah right, that is basically the same issue I was thinking of for a
> subsequent zpci_register_ioat(). What about the obvious one. Just call
> synchronize_rcu() before zpci_unregister_ioat()?
Ah, it can be done, but be prepared to wait >> 1s for synchronize_rcu
to complete in some cases.
What you have seems like it could be OK, just deal with the ugly racy
failure
Jason
next prev parent reply other threads:[~2022-10-21 13:36 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-18 14:51 [PATCH 0/5] iommu/s390: Further improvements Niklas Schnelle
2022-10-18 14:51 ` [PATCH 1/5] iommu/s390: Make attach succeed even if the device is in error state Niklas Schnelle
2022-10-28 15:55 ` Matthew Rosato
2022-10-18 14:51 ` [PATCH 2/5] iommu/s390: Add I/O TLB ops Niklas Schnelle
2022-10-28 16:03 ` Matthew Rosato
2022-10-31 16:11 ` Robin Murphy
2022-11-02 10:51 ` Niklas Schnelle
2022-10-18 14:51 ` [PATCH 3/5] iommu/s390: Use RCU to allow concurrent domain_list iteration Niklas Schnelle
2022-10-18 15:18 ` Jason Gunthorpe
2022-10-19 8:31 ` Niklas Schnelle
2022-10-19 11:53 ` Jason Gunthorpe
2022-10-20 8:51 ` Niklas Schnelle
2022-10-20 11:05 ` Jason Gunthorpe
2022-10-21 12:08 ` Niklas Schnelle
2022-10-21 13:36 ` Jason Gunthorpe [this message]
2022-10-21 15:01 ` Niklas Schnelle
2022-10-21 15:04 ` Jason Gunthorpe
2022-10-24 15:22 ` Niklas Schnelle
2022-10-24 16:26 ` Jason Gunthorpe
2022-10-27 12:44 ` Niklas Schnelle
2022-10-27 12:56 ` Jason Gunthorpe
2022-10-27 13:35 ` Niklas Schnelle
2022-10-27 14:03 ` Jason Gunthorpe
2022-10-28 9:29 ` Niklas Schnelle
2022-10-28 11:28 ` Jason Gunthorpe
2022-10-21 15:05 ` Niklas Schnelle
2022-10-18 14:51 ` [PATCH 4/5] iommu/s390: Optimize IOMMU table walking Niklas Schnelle
2022-10-18 14:51 ` [PATCH 5/5] s390/pci: use lock-free I/O translation updates Niklas Schnelle
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