linux-kernel - Re: [patch 6/9] signalfd/timerfd v3

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Date:	Sun, 11 Mar 2007 16:13:33 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 6/9] signalfd/timerfd v3 - timerfd core ...

On Sun, 11 Mar 2007, Davide Libenzi wrote:

> This patch introduces a new system call for timers events delivered
> though file descriptors. This allows timer event to be used with
> standard POSIX poll(2), select(2) and read(2). As a consequence of
> supporting the Linux f_op->poll subsystem, they can be used with
> epoll(2) too.
> The system call is defined as:
> 
> int timerfd(int ufd, int clockid, int tmrtype, const struct timespec *utmr);
> 
> The "ufd" parameter allows for re-use (re-programming) of an existing
> timerfd w/out going through the close/open cycle (same as signalfd).
> If "ufd" is -1, s new file descriptor will be created, otherwise the
> existing "ufd" will be re-programmed.
> The "clockid" parameter is either CLOCK_MONOTONIC or CLOCK_REALTIME.
> The "tmrtype" parameter allows to specify the timer type. The following
> values are supported:
> 
>     TFD_TIMER_REL
>         The time specified in the "utmr" parameter is a relative time
> 	from NOW.
> 
>     TFD_TIMER_ABS
>         The timer specified in the "utmr" parameter is an absolute time.
> 
>     TFD_TIMER_SEQ
>         The time specified in the "utmr" parameter is an interval at
> 	which a continuous clock rate will be generated.
> 

Duh! Forgot to update the documenation. Now timerfd() gets an itimerspec.
For TFD_TIMER_REL only the it_interval is valid, and it's the relative 
time. For TFD_TIMER_ABS, only the it_value is valid, and that the expiry 
absolute time. For TFD_TIMER_SEQ, it_value tells when the first tick 
should be generated, and it_interval tells the period of the following 
ticks.



- Davide

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