Jason Gunthorpe <[email protected]> wrote on 02/09/2016
01:20:13 PM:
> Subject: Re: [tpmdd-devel] [PATCH v5 4/5] Initialize TPM and get
> durations and timeouts
>
> On Tue, Feb 09, 2016 at 01:11:58PM -0500, Stefan Berger wrote:
>
> > :-( User space will just pass the fd to another process, which is the
TPM
> > emulator, and that thing then starts failing on the broken file
descriptor.
>
> .. and then it exits like any other failure and the caller has to sort
> it out, which it already has to handle.
>
> > Either way, I don't see how the TPM emulator can be fully operational
before
> > tpm_chip_register() is called.
>
> You still haven't said what is wrong with doing all the work in a work
> queue so user space can respond normally without all this ugly hacking.
It doesn't seem right to simply close the file descriptor on the process
if something goes wrong. The process couldn't close() on it since another
thread could have gotten the same fd number for something else. I haven't
seen a file descriptor that one must not close() in user space.
It doesn't seem to work to only close the file (fput()) in case something
goes wrong while sending the commands to the TPM and before the
tpm_chip_register(). In that case I see the message 'VFS: Close: file
count is 0' once the application closes the fd.
Do you have any insights?
Stefan
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