linux-kernel - Re: [PATCH v3 0/2] tpm: add support for nonblocking operation

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Message-ID: <0e46c2e9-af2b-550f-2b3d-98cbc1840bc1@gmail.com>
Date:   Wed, 20 Jun 2018 18:24:32 -0700
From:   Tadeusz Struk <tstruk@...il.com>
To:     James Bottomley <James.Bottomley@...senPartnership.com>,
        Tadeusz Struk <tadeusz.struk@...el.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     jgg@...pe.ca, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, philip.b.tricca@...el.com,
        "Dock, Deneen T" <deneen.t.dock@...el.com>
Subject: Re: [PATCH v3 0/2] tpm: add support for nonblocking operation

On 06/20/2018 04:59 PM, James Bottomley wrote:
> I'm slightly surprised by this statement.  I thought IoT Node.js
> runtimes (of which there are far too many, so I haven't looked at all
> of them) use libuv or one of the forks:
> 
> http://libuv.org/
> 
> As the basis for their I/O handling?  While libuv can do polling for
> event driven interfaces it also support the worker thread model just as
> easily:
> 
> http://docs.libuv.org/en/v1.x/threadpool.html

Yes, it does polling:
http://docs.libuv.org/en/v1.x/design.html#the-i-o-loop

> 
>> Similarly embedded applications, which are basically just a single
>> threaded event loop, quite often don't use threads because of
>> resources constrains.
> It's hard for me, as a kernel developer, to imagine any embedded
> scenario using the Linux kernel that would not allow threads unless the
> writers simply didn't bother with synchronization: The kernel schedules
> at the threads level and can't be configured not to use them plus
> threads are inherently more lightweight than processes so they're a
> natural fit for resource constrained scenarios.
> 
> That's still not to say we shouldn't do this, but I've got to say I
> think the only consumers would be old fashioned C code: the code we
> used to write before we had thread libraries that did use signals and
> poll() for a single threaded event driven monolith (think green
> threads), because all the new webby languages use threading either
> explicitly or at the core of their operation.

Regardless of how it actually might be used, I'm happy that we agree on
that this *is* the right thing to do.
Thanks,
Tadeusz