linux-kernel - Re: [PATCH] tpm: don't destroy chip device prematurely

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Message-ID: <20161006162245.GF1224@obsidianresearch.com>
Date:   Thu, 6 Oct 2016 10:22:45 -0600
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     "Winkler, Tomas" <tomas.winkler@...el.com>,
        "tpmdd-devel@...ts.sourceforge.net" 
        <tpmdd-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: don't destroy chip device prematurely

On Thu, Oct 06, 2016 at 02:23:57PM +0300, Jarkko Sakkinen wrote:

> I think that they should be fenced then for the sake of consistency.
> I do not see why sysfs code is privileged not to do fencing while other
> peers have to do it.

Certainly the locking could be changed, but it would be nice to have a
reason other than aesthetics.

sysfs is not unique, we also do not grab the rwlock lock during any
commands executed as part of probe. There are basically two locking
regimes - stuff that is proven to by synchronous with probe/remove
(sysfs, probe cmds) and everything else (kapi, cdev)

Further, the current sysfs implementation is nice and sane: the file
accesses cannot fail with ENODEV. That is a useful concrete property
and I don't think we should change it without a good reason.

Jason