From: Colin Walters <walters@verbum.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: TFD_CANCEL_ON_SET race when making a wall clock
Date: Fri, 02 Sep 2011 11:07:37 -0400 [thread overview]
Message-ID: <1314976058.30505.18.camel@lenny> (raw)
In-Reply-To: <alpine.LFD.2.02.1109021655140.2723@ionos>
Hi Thomas,
On Fri, 2011-09-02 at 17:00 +0200, Thomas Gleixner wrote:
> There is no way to handle:
>
> clock_gettime(a);
> clock_settime();
> timerfd_create();
> timerfd_settime(a + x);
>
> And there wont be one ever.
Well, you can see what I did in userspace - require the processes' idea
of the current time to be passed in, and check after calling
timerfd_settime() - did the clock go backwards? Ok, treat the timerfd
source as ready.
If we wanted to avoid userspace having to do this, we *could* make a new
system call which also took the "expected current time". But it's
probably not worth doing so given that the userspace workaround isn't
too difficult.
So, I think you confirmed what I'm saying, we should just document this
and move on. Thanks!
prev parent reply other threads:[~2011-09-02 15:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-02 14:37 Colin Walters
2011-09-02 15:00 ` Thomas Gleixner
2011-09-02 15:07 ` Colin Walters [this message]
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