linux-kernel - Re: [RFC PATCH 0/3] epoll: read(),write(),ioctl() interface

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Message-ID: <52EFEF0A.9080101@amacapital.net>
Date:	Mon, 03 Feb 2014 11:33:30 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Nathaniel Yazdani <n1ght.4nd.d4y@...il.com>,
	viro@...iv.linux.org.uk
CC:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] epoll: read(),write(),ioctl() interface

On 02/02/2014 06:17 PM, Nathaniel Yazdani wrote:
> Hi everyone,
> 
> This patch series adds support for read(), write(), and ioctl() operations
> on eventpolls as well as an associated userspace structure to format the
> eventpoll entries delivered via read()/write() buffers. The new structure,
> struct epoll, differs from struct epoll_event mainly in that it also holds
> the associated file descriptor. Using the normal I/O interface to manipulate
> eventpolls is much neater than using epoll-specific syscalls while also
> allowing for greater flexibility (theoretically, pipes could be used to
> filter access). Specifically, write() creates, modifies, and/or removes event
> entries stored in the supplied buffer, using the userspace identifier to
> check whether an entry exists and removing it if no events are set to trigger
> it, while read() simply waits for enough events to fill the provided buffer.
> As timeout control is essential for polling to be practical, ioctl() is used
> to configure an optional timeout, which is infinite by default.

If major changes are made to the epoll API, I want a way to do a bunch
of EPOLL_CTL_MODs and a wait, all in one syscall.  Even better: allow
more flexible timeouts (CLOCK_MONOTONIC, CLOCK_REALTIME, etc) at the
same time.

Since this can't do that, I'm not terribly inspired.

--Andy

> 
>  Documentation/ioctl/ioctl-number.txt |   1 +
>  fs/eventpoll.c                       | 534 ++++++++++++++++++++++++-----------
>  include/uapi/linux/eventpoll.h       |  10 +
>  3 files changed, 384 insertions(+), 161 deletions(-)
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