linux-kernel - Re: [PATCH] tpm: Make timeout logic simpler and more robust

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Message-ID: <20190312123632.GB9243@linux.intel.com>
Date:   Tue, 12 Mar 2019 14:36:32 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Calvin Owens <calvinowens@...com>
Cc:     Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH] tpm: Make timeout logic simpler and more robust

On Mon, Mar 11, 2019 at 04:54:04PM -0700, Calvin Owens wrote:
> We're having lots of problems with TPM commands timing out, and we're
> seeing these problems across lots of different hardware (both v1/v2).
> 
> I instrumented the driver to collect latency data, but I wasn't able to
> find any specific timeout to fix: it seems like many of them are too
> aggressive. So I tried replacing all the timeout logic with a single
> universal long timeout, and found that makes our TPMs 100% reliable.
> 
> Given that this timeout logic is very complex, problematic, and appears
> to serve no real purpose, I propose simply deleting all of it.
> 
> Signed-off-by: Calvin Owens <calvinowens@...com>

Have been thinking about this and I do agree. It has been like that
before my times with this subsystem so when I did the original TPM2
patches I carried this logic albeit even at that point I did not get it.
Now that I've been maintaining for over three years I'm confident that
this the Right Thing to do.

/Jarkko