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From: Dan Williams <dan.j.williams@intel.com>
To: Ben Widawsky <ben.widawsky@intel.com>
Cc: linux-cxl@vger.kernel.org, Linux NVDIMM <nvdimm@lists.linux.dev>,
	 Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Vishal L Verma <vishal.l.verma@intel.com>,
	 "Schofield, Alison" <alison.schofield@intel.com>,
	"Weiny, Ira" <ira.weiny@intel.com>
Subject: Re: [PATCH 17/23] cxl/mbox: Add exclusive kernel command support
Date: Tue, 10 Aug 2021 19:14:45 -0700	[thread overview]
Message-ID: <CAPcyv4jn-1V=nCdgOxFJF3bVJd13YpRxnLvjE_BbacJ7_Qmwhw@mail.gmail.com> (raw)
In-Reply-To: <CAPcyv4iLLPR+yijKNHceEKM4+fKQ4i6r+ZLYH+_b-ao6tznHLQ@mail.gmail.com>

On Tue, Aug 10, 2021 at 6:22 PM Dan Williams <dan.j.williams@intel.com> wrote:
[..]
> > > > What's the concurrency this lock is trying to protect against?
> > >
> > > I can add a comment. It synchronizes against in-flight ioctl users to
> > > make sure that any requests have completed before the policy changes.
> > > I.e. do not allow userspace to race the nvdimm subsystem attaching to
> > > get a consistent state of the persistent memory configuration.
> > >
> >
> > Ah, so the expectation is that these things will be set not just on
> > probe/unregister()? I would assume an IOCTL couldn't happen while
> > probe/unregister is happening.
>
> The ioctl is going through the cxl_pci driver. That driver has
> finished probe and published the ioctl before this lockout can run in
> cxl_nvdimm_probe(), so it's entirely possible that label writing
> ioctls are in progress when cxl_nvdimm_probe() eventually fires.
>
> The current policy for /sys/bus/nd/devices/nmemX devices are that
> label writes are allowed as long as the nmemX device is not active in
> any region. I was thinking the CXL policy is coarser. Label writes via
> /sys/bus/cxl/devices/memX ioctls are disallowed as long as the bridge
> for that device into the nvdimm subsystem is active.

Oh, whoops, the mbox_mutex is not taken until we're deep inside
mbox_send. So this synchronization needs to move to the cxl_memdev
rwsem. Thanks for the nudge, I missed that.

  reply	other threads:[~2021-08-11  2:14 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-09 22:27 [PATCH 00/23] cxl_test: Enable CXL Topology and UAPI regression tests Dan Williams
2021-08-09 22:27 ` [PATCH 01/23] libnvdimm/labels: Introduce getters for namespace label fields Dan Williams
2021-08-10 20:48   ` Ben Widawsky
2021-08-10 21:58     ` Dan Williams
2021-08-11 18:44   ` Jonathan Cameron
2021-08-09 22:27 ` [PATCH 02/23] libnvdimm/labels: Add isetcookie validation helper Dan Williams
2021-08-11 18:44   ` Jonathan Cameron
2021-08-09 22:28 ` [PATCH 03/23] libnvdimm/labels: Introduce label setter helpers Dan Williams
2021-08-11 17:27   ` Jonathan Cameron
2021-08-11 17:42     ` Dan Williams
2021-08-09 22:28 ` [PATCH 04/23] libnvdimm/labels: Add a checksum calculation helper Dan Williams
2021-08-11 18:44   ` Jonathan Cameron
2021-08-09 22:28 ` [PATCH 05/23] libnvdimm/labels: Add blk isetcookie set / validation helpers Dan Williams
2021-08-11 18:45   ` Jonathan Cameron
2021-08-09 22:28 ` [PATCH 06/23] libnvdimm/labels: Add blk special cases for nlabel and position helpers Dan Williams
2021-08-11 18:45   ` Jonathan Cameron
2021-08-09 22:28 ` [PATCH 07/23] libnvdimm/labels: Add type-guid helpers Dan Williams
2021-08-11 18:46   ` Jonathan Cameron
2021-08-09 22:28 ` [PATCH 08/23] libnvdimm/labels: Add claim class helpers Dan Williams
2021-08-11 18:46   ` Jonathan Cameron
2021-08-09 22:28 ` [PATCH 09/23] libnvdimm/labels: Add address-abstraction uuid definitions Dan Williams
2021-08-11 18:49   ` Jonathan Cameron
2021-08-11 22:47     ` Dan Williams
2021-08-09 22:28 ` [PATCH 10/23] libnvdimm/labels: Add uuid helpers Dan Williams
2021-08-11  8:05   ` Andy Shevchenko
2021-08-11 16:59     ` Andy Shevchenko
2021-08-11 17:11       ` Dan Williams
2021-08-11 19:18         ` Andy Shevchenko
2021-08-11 19:26           ` Dan Williams
2021-08-12 22:34           ` Dan Williams
2021-08-13 10:14             ` Andy Shevchenko
2021-08-14  7:35               ` Christoph Hellwig
2021-08-11 18:13   ` Jonathan Cameron
2021-08-12 21:17     ` Dan Williams
2021-08-09 22:28 ` [PATCH 11/23] libnvdimm/labels: Introduce CXL labels Dan Williams
2021-08-11 18:41   ` Jonathan Cameron
2021-08-11 23:01     ` Dan Williams
2021-08-09 22:28 ` [PATCH 12/23] cxl/pci: Make 'struct cxl_mem' device type generic Dan Williams
2021-08-09 22:28 ` [PATCH 13/23] cxl/mbox: Introduce the mbox_send operation Dan Williams
2021-08-09 22:29 ` [PATCH 14/23] cxl/mbox: Move mailbox and other non-PCI specific infrastructure to the core Dan Williams
2021-08-11  6:11   ` [PATCH v2 " Dan Williams
2021-08-09 22:29 ` [PATCH 15/23] cxl/pci: Use module_pci_driver Dan Williams
2021-08-09 22:29 ` [PATCH 16/23] cxl/mbox: Convert 'enabled_cmds' to DECLARE_BITMAP Dan Williams
2021-08-09 22:29 ` [PATCH 17/23] cxl/mbox: Add exclusive kernel command support Dan Williams
2021-08-10 21:34   ` Ben Widawsky
2021-08-10 21:52     ` Dan Williams
2021-08-10 22:06       ` Ben Widawsky
2021-08-11  1:22         ` Dan Williams
2021-08-11  2:14           ` Dan Williams [this message]
2021-08-09 22:29 ` [PATCH 18/23] cxl/pmem: Translate NVDIMM label commands to CXL label commands Dan Williams
2021-08-09 22:29 ` [PATCH 19/23] cxl/pmem: Add support for multiple nvdimm-bridge objects Dan Williams
2021-08-09 22:29 ` [PATCH 20/23] tools/testing/cxl: Introduce a mocked-up CXL port hierarchy Dan Williams
2021-08-10 21:57   ` Ben Widawsky
2021-08-10 22:40     ` Dan Williams
2021-08-11 15:18       ` Ben Widawsky
     [not found]       ` <xp0k4.l2r85dw1p7do@intel.com>
2021-08-11 21:03         ` Dan Williams
2021-08-09 22:29 ` [PATCH 21/23] cxl/bus: Populate the target list at decoder create Dan Williams
2021-08-09 22:29 ` [PATCH 22/23] cxl/mbox: Move command definitions to common location Dan Williams
2021-08-09 22:29 ` [PATCH 23/23] tools/testing/cxl: Introduce a mock memory device + driver Dan Williams
2021-08-10 22:10 ` [PATCH 00/23] cxl_test: Enable CXL Topology and UAPI regression tests Ben Widawsky
2021-08-10 22:58   ` Dan Williams

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