linux-kernel - Re: [PATCH v4 2/2] tpm: add support for nonblocking operation

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Date:   Fri, 10 Aug 2018 12:00:47 -0700
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     Tadeusz Struk <tadeusz.struk@...el.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     flihp@...bit.us, jgg@...pe.ca, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] tpm: add support for nonblocking operation

On Fri, 2018-08-10 at 11:56 -0700, Tadeusz Struk wrote:
> On 08/10/2018 11:48 AM, James Bottomley wrote:
> > On Fri, 2018-08-10 at 11:21 -0700, Tadeusz Struk wrote:
> > > and the feedback I got from Jason was:
> > > 
> > > "I wonder if it is worth creating this when the first file is
> > > opened.. Lots of systems have TPMs but few use the userspace.."
> > > 
> > > so I changed this to allocate the WQ on first open. I think it
> > > makes sense, but I leave it to you to decide.
> > 
> > If the reason is to not create a wq unless it's needed, shouldn't
> > the condition actually be first open with flag O_NONBLOCK?
> > 
> 
> Not really because one can do:
> 
> int fd = open("/dev/tpm0", O_RDWR);
> fcntl(fd, F_SETFL, O_NONBLOCK);

so move the condition to first need to queue ...

James