To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
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Cc: Bjorn Helgaas <helgaas@kernel.org>,
        Keith Busch <keith.busch@intel.com>,
        Myron Stowe <myron.stowe@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Jonathan Corbet <corbet@lwn.net>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Emil Velikov <emil.l.velikov@gmail.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>,
        Stefan Berger <stefanb@linux.vnet.ibm.com>, Wei Zhang <wzhang@fb.com>,
        Kurt Schwemmer <kurt.schwemmer@microsemi.com>,
        Stephen Bates <stephen.bates@microsemi.com>, linux-pci@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-kernel@vger.kernel.org
From: Logan Gunthorpe <logang@deltatee.com>
Message-ID: <8e20a911-988b-b486-4530-2525efc8b2c2@deltatee.com>
Date: Wed, 1 Mar 2017 17:29:27 -0700
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On 01/03/17 05:23 PM, Logan Gunthorpe wrote:
> Because of how poll works, I don't see how I can just hold a semaphore
> inside every fops call like the tpm code does.

On 01/03/17 04:58 PM, Jason Gunthorpe wrote:
> Both infiniband and TPM have the 'detach' flavour of unplug where the
> user is not forced to close their open cdevs. For simpler cases you
> can just wait for all cdevs to close with a simple rwsem, much like
> sysfs does already during device_del.

Though, after reading your email again, a hard fence on close sounds
like a good idea. Tomorrow I'll post a v6 that uses that approach.


Thanks,

Logan