linux-kernel - Re: [PATCH 0/2] eventfd: simplify signal helpers

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Message-ID: <ZLW8wEzkhBxd0O0L@ziepe.ca>
Date:   Mon, 17 Jul 2023 19:12:16 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     Grzegorz Jaszczyk <jaz@...ihalf.com>,
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Subject: Re: [PATCH 0/2] eventfd: simplify signal helpers

On Mon, Jul 17, 2023 at 01:08:31PM -0600, Alex Williamson wrote:

> What would that mechanism be?  We've been iterating on getting the
> serialization and buffering correct, but I don't know of another means
> that combines the notification with a value, so we'd likely end up with
> an eventfd only for notification and a separate ring buffer for
> notification values.

All FDs do this. You just have to make a FD with custom
file_operations that does what this wants. The uAPI shouldn't be able
to tell if the FD is backing it with an eventfd or otherwise. Have the
kernel return the FD instead of accepting it. Follow the basic design
of eg mlx5vf_save_fops

Jason