linux-kernel - Re: [PATCH v5 0/4] New Microsemi PCI Switch Management Driver

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Message-ID: <8e20a911-988b-b486-4530-2525efc8b2c2@deltatee.com>
Date:   Wed, 1 Mar 2017 17:29:27 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Keith Busch <keith.busch@...el.com>,
        Myron Stowe <myron.stowe@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Jonathan Corbet <corbet@....net>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Wei Zhang <wzhang@...com>,
        Kurt Schwemmer <kurt.schwemmer@...rosemi.com>,
        Stephen Bates <stephen.bates@...rosemi.com>,
        linux-pci@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/4] New Microsemi PCI Switch Management Driver



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