linux-kernel - Re: Tesing of / bugs in new timerfd API

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Message-ID: <cfd18e0f0712170527k6e2f20ddq8d3abc367aa20661@mail.gmail.com>
Date:	Mon, 17 Dec 2007 14:27:23 +0100
From:	"Michael Kerrisk" <mtk.manpages@...glemail.com>
To:	"Davide Libenzi" <davidel@...ilserver.org>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>, tytso@...nk.org,
	"Thomas Gleixner" <tglx@...utronix.de>, "Greg KH" <gregkh@...e.de>,
	"Christoph Hellwig" <hch@....de>,
	"Linux Torvalds" <torvalds@...ux-foundation.org>
Subject: Re: Tesing of / bugs in new timerfd API

Hi Davide,

On 12/16/07, Davide Libenzi <davidel@...ilserver.org> wrote:
> On Fri, 14 Dec 2007, Michael Kerrisk wrote:
>
> > You snipped my example that demonstrated the problem.  Both of the
> > following runs create a timer that expires 10 seconds from "now", but
> > observe the difference in the value returned by timerfd_gettime():
> >
> > $ ./timerfd_test 10         # does not use TFD_TIMER_ABSTIME
> > Initial setting for settime:   value=10.000, interval=0.000
> > ./timerfd_test> g
> > (elapsed time=  1)
> > Current value:                 value=346.448, interval=0.000
> >
> > $ ./timerfd_test -a 10      # uses TFD_TIMER_ABSTIME
> > Initial setting for settime:   value=1197630855.254, interval=0.000
> > ./timerfd_test> g
> > (elapsed time=  1)
> > Current value:                 value=1197630855.254, interval=0.000
> >
> > Either there's an inconsistency here depending on the use of
> > TFD_TIMER_ABSTIME, or there is a bug in my understanding or my test
> program
> > (but so far I haven't spotted that bug ;-).).
>
> Can you try the two patches below? I tried them on my 32 bit box (one of
> the rare beasts still lingering around here) and it seems to be working
> fine (those go on top of the previous ones).

Against 2.6.24-rc5, I applied first your earlier patches ("v3") and
then the newest patch.  My tests confirm that:

> This fixed the 32 bit tick-count truncation, and makes the time returned
> to be the remaining time till the next expiration.

Are you going to resubmit a new patch set that includes these latest changes?

Michael
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