From: Vinicius Costa Gomes <vinicius.gomes@intel•com>
To: Xabier Marquiegui <xabier.marquiegui@gmail•com>
Cc: alex.maftei@amd•com, chrony-dev@chrony•tuxfamily.org,
davem@davemloft•net, horms@kernel•org, mlichvar@redhat•com,
netdev@vger•kernel.org, ntp-lists@mattcorallo•com,
reibax@gmail•com, richardcochran@gmail•com,
rrameshbabu@nvidia•com, shuah@kernel•org
Subject: Re: [PATCH net-next v2 2/3] ptp: support multiple timestamp event readers
Date: Wed, 13 Sep 2023 14:25:48 -0700 [thread overview]
Message-ID: <87wmwtojdv.fsf@intel.com> (raw)
In-Reply-To: <20230913085737.2214180-1-xmarquiegui@ainguraiiot.com>
Xabier Marquiegui <xabier.marquiegui@gmail•com> writes:
>> Using the pid of the task will break when using some form of file
>> descriptor passing. e.g. Task A opened the chardev, called the ioctl()
>> with some mask and then passed the fd to Task B, that's actually going
>> to use the fd.
>>
>> Is this something that we want to support? Am I missing something?
>
> Thank you very much for your valuable comments Vinicius,
>
> Let me try to confirm if I understand what you are observing here.
>
> Let's say we have a process with two threads. One of them opens the device
> file to do IOCTL operations, and the other one opens the device file to
> read timestamp events. Since both have the same PID, all the operations
> (read,release...) would fail because I designed them under the assumption
> that only one open operation would happen per PID.
>
I was initially thinking about another scenario: when Process A passes
the open file descriptor via SCM_RIGHTS to Process B.
But your scenario also shows the limitations of the current approach.
> This is indeed not as safe as it should be and I should try to improve it.
>
> I am already looking at alternatives, but maybe someone can give me a hint.
> Do you have any suggestions on what I could do to have file operations
> (read, release...) determine which open instance they belong to?
Taking a quick look, it seems that you would have to change 'struct
posix_clock_file_operations' to also pass around the 'struct file' of
the file being used.
That way we can track each user/"open()". And if one program decides
that it needs to have have multiple fds with different masks, and so
different queues, it should just work.
What do you think?
Cheers,
--
Vinicius
next prev parent reply other threads:[~2023-09-13 21:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-12 22:02 [PATCH net-next v2 1/3] ptp: Replace timestamp event queue with linked list Xabier Marquiegui
2023-09-12 22:02 ` [PATCH net-next v2 2/3] ptp: support multiple timestamp event readers Xabier Marquiegui
2023-09-13 0:10 ` Vinicius Costa Gomes
2023-09-13 8:57 ` Xabier Marquiegui
2023-09-13 21:25 ` Vinicius Costa Gomes [this message]
2023-09-14 10:02 ` Xabier Marquiegui
2023-09-14 15:09 ` Richard Cochran
2023-09-14 17:12 ` Vinicius Costa Gomes
2023-09-19 15:15 ` kernel test robot
2023-09-12 22:02 ` [PATCH net-next v2 3/3] ptp: support event queue reader channel masks Xabier Marquiegui
2023-09-13 0:05 ` [PATCH net-next v2 1/3] ptp: Replace timestamp event queue with linked list Vinicius Costa Gomes
2023-09-13 7:56 ` Jiri Pirko
2023-09-14 14:21 ` Richard Cochran
2023-09-20 15:40 ` kernel test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87wmwtojdv.fsf@intel.com \
--to=vinicius.gomes@intel$(echo .)com \
--cc=alex.maftei@amd$(echo .)com \
--cc=chrony-dev@chrony$(echo .)tuxfamily.org \
--cc=davem@davemloft$(echo .)net \
--cc=horms@kernel$(echo .)org \
--cc=mlichvar@redhat$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
--cc=ntp-lists@mattcorallo$(echo .)com \
--cc=reibax@gmail$(echo .)com \
--cc=richardcochran@gmail$(echo .)com \
--cc=rrameshbabu@nvidia$(echo .)com \
--cc=shuah@kernel$(echo .)org \
--cc=xabier.marquiegui@gmail$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox