From: Al Viro <viro@ZenIV.linux.org.uk>
To: Gustavo Padovan <gustavo@padovan.org>
Cc: linux-media@vger.kernel.org, Hans Verkuil <hverkuil@xs4all.nl>,
Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
Shuah Khan <shuahkh@osg.samsung.com>,
linux-kernel@vger.kernel.org,
Gustavo Padovan <gustavo.padovan@collabora.com>,
linux-fsdevel@vger.kernel.org,
Riley Andrews <riandrews@android.com>
Subject: Re: [PATCH v3 14/15] fs/files: export close_fd() symbol
Date: Thu, 7 Sep 2017 21:36:11 +0100 [thread overview]
Message-ID: <20170907203610.GX5426@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20170907184226.27482-15-gustavo@padovan.org>
On Thu, Sep 07, 2017 at 03:42:25PM -0300, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.com>
>
> Rename __close_fd() to close_fd() and export it to be able close files
> in modules using file descriptors.
>
> The usecase that motivates this change happens in V4L2 where we send
> events to userspace with a fd that has file installed in it. But if for
> some reason we have to cancel the video stream we need to close the files
> that haven't been shared with userspace yet. Thus the export of
> close_fd() becomes necessary.
>
> fd_install() happens when we call an ioctl to queue a buffer, but we only
> share the fd with userspace later, and that may happen in a kernel thread
> instead.
NAK. As soon as the reference is in descriptor table, you *can't* do anything
to it. This "sharing" part is complete BS - being _told_ that descriptor is
there does not matter at all. That descriptor might be hit with dup2() as
soon as fd_install() has happened. Or be closed, or any number of other things.
You can not take it back. Once fd_install() is done, it's fucking done, period.
If V4L2 requires removing it from descriptor table, it's a shitty API and needs
to be fixed.
Again, NAK.
next prev parent reply other threads:[~2017-09-07 20:36 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-07 18:42 [PATCH v3 00/15] V4L2 Explicit Synchronization support Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 01/15] [media] v4l: Document explicit synchronization behaviour Gustavo Padovan
2017-09-08 2:39 ` Nicolas Dufresne
2017-09-11 10:50 ` Hans Verkuil
2017-09-11 11:01 ` Hans Verkuil
2017-09-11 13:18 ` Gustavo Padovan
2017-09-11 13:26 ` Hans Verkuil
2017-09-11 13:34 ` Gustavo Padovan
2017-09-11 13:35 ` Hans Verkuil
2017-09-07 18:42 ` [PATCH v3 02/15] [media] vb2: add explicit fence user API Gustavo Padovan
2017-09-11 10:55 ` Hans Verkuil
2017-09-11 11:03 ` Hans Verkuil
2017-10-02 13:42 ` Brian Starkey
2017-10-04 20:12 ` Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 03/15] [media] vb2: check earlier if stream can be started Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 04/15] [media] vb2: add in-fence support to QBUF Gustavo Padovan
2017-10-02 13:43 ` Brian Starkey
2017-09-07 18:42 ` [PATCH v3 05/15] [media] uvc: enable subscriptions to other events Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 06/15] [media] vivid: assign the specific device to the vb2_queue->dev Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 07/15] [media] v4l: add V4L2_EVENT_BUF_QUEUED event Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 08/15] [media] vb2: add .buffer_queued() to notify queueing in the driver Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 09/15] [media] v4l: add support to BUF_QUEUED event Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 10/15] [media] vb2: add 'ordered' property to queues Gustavo Padovan
2017-10-02 13:43 ` Brian Starkey
2017-10-04 20:18 ` Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 11/15] [media] vivid: mark vivid queues as ordered Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 12/15] [media] vb2: add videobuf2 dma-buf fence helpers Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 13/15] [media] vb2: add infrastructure to support out-fences Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 14/15] fs/files: export close_fd() symbol Gustavo Padovan
2017-09-07 18:51 ` Eric Biggers
2017-09-07 20:36 ` Al Viro [this message]
2017-09-07 21:22 ` Gustavo Padovan
2017-09-07 22:03 ` Al Viro
2017-09-07 22:09 ` Hans Verkuil
2017-09-07 22:18 ` Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 15/15] [media] vb2: add out-fence support to QBUF Gustavo Padovan
2017-10-02 13:41 ` [PATCH v3 00/15] V4L2 Explicit Synchronization support Brian Starkey
2017-10-04 20:08 ` Gustavo Padovan
2017-10-13 1:56 ` Brian Starkey
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