From: Dan Williams <dan.j.williams@intel.com>
To: Jane Chu <jane.chu@oracle.com>
Cc: linux-nvdimm <linux-nvdimm@lists.01.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Linux MM" <linux-mm@kvack.org>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Christoph Hellwig" <hch@lst.de>
Subject: Re: [PATCH v2 0/6] mm/devm_memremap_pages: Fix page release race
Date: Thu, 16 May 2019 14:51:40 -0700 [thread overview]
Message-ID: <CAPcyv4hujnGHtTwE78gvmEoY3Y6nLsd1AhJfeKMwHrxLvStf9w@mail.gmail.com> (raw)
In-Reply-To: <d699e312-0e88-30c7-8e50-ff624418d486@oracle.com>
On Thu, May 16, 2019 at 9:45 AM Jane Chu <jane.chu@oracle.com> wrote:
>
> Hi,
>
> I'm able to reproduce the panic below by running two sets of ndctl
> commands that actually serve legitimate purpose in parallel (unlike
> the brute force experiment earlier), each set in a indefinite loop.
> This time it takes about an hour to panic. But I gather the cause
> is probably the same: I've overlapped ndctl commands on the same
> region.
>
> Could we add a check in nd_ioctl(), such that if there is
> an ongoing ndctl command on a region, subsequent ndctl request
> will fail immediately with something to the effect of EAGAIN?
> The rationale being that kernel should protect itself against
> user mistakes.
We do already have locking in the driver to prevent configuration
collisions. The problem looks to be broken assumptions about running
the device unregistration path in a separate thread outside the lock.
I suspect it may be incorrect assumptions about the userspace
visibility of the device relative to teardown actions. To be clear
this isn't the nd_ioctl() path this is the sysfs path.
> Also, sensing the subject fix is for a different problem, and has been
> verified, I'm happy to see it in upstream, so we have a better
> code base to digger deeper in terms of how the destructive ndctl
> commands interacts to typical mission critical applications, include
> but not limited to rdma.
Right, the crash signature you are seeing looks unrelated to the issue
being address in these patches which is device-teardown racing active
page pins. I'll start the investigation on the crash signature, but
again I don't think it reads on this fix series.
next prev parent reply other threads:[~2019-05-16 21:51 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-07 23:55 [PATCH v2 0/6] mm/devm_memremap_pages: Fix page release race Dan Williams
2019-05-07 23:56 ` [PATCH v2 1/6] drivers/base/devres: Introduce devm_release_action() Dan Williams
2019-05-14 19:12 ` Greg Kroah-Hartman
2019-05-14 19:24 ` Dan Williams
2019-05-07 23:56 ` [PATCH v2 2/6] mm/devm_memremap_pages: Introduce devm_memunmap_pages Dan Williams
2019-05-07 23:56 ` [PATCH v2 3/6] PCI/P2PDMA: Fix the gen_pool_add_virt() failure path Dan Williams
2019-05-07 23:56 ` [PATCH v2 4/6] lib/genalloc: Introduce chunk owners Dan Williams
2019-05-07 23:56 ` [PATCH v2 5/6] PCI/P2PDMA: Track pgmap references per resource, not globally Dan Williams
2019-05-07 23:56 ` [PATCH v2 6/6] mm/devm_memremap_pages: Fix final page put race Dan Williams
2019-05-08 17:05 ` [PATCH v2 0/6] mm/devm_memremap_pages: Fix page release race Logan Gunthorpe
2019-05-13 19:22 ` Logan Gunthorpe
2019-05-14 18:51 ` Jane Chu
2019-05-14 19:04 ` Dan Williams
2019-05-14 21:18 ` Jane Chu
2019-05-16 16:45 ` Jane Chu
2019-05-16 21:42 ` jane.chu
2019-05-16 21:51 ` Dan Williams [this message]
2019-05-17 0:01 ` Jane Chu
2019-05-31 4:17 ` Dan Williams
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