On Wed, Jun 11, 2014 at 01:52:46PM +0400, Cyrill Gorcunov wrote:
> On Wed, Jun 11, 2014 at 01:09:15PM +0400, Andrew Vagin wrote:
> > On Wed, Jun 11, 2014 at 11:51:25AM +0400, Cyrill Gorcunov wrote:
> > > On Wed, Jun 11, 2014 at 11:27:43AM +0400, Andrew Vagin wrote:
> >
> > Setting ticks to zero is equivalent to timerfd_read(), isn't it?
> > So do we need to re-arme the timer, if it's periodic?
>
> I must admit I'm not really sure if we should rearm it in such
> case. In general @ticks are zeroified in case of timer-setup/cancel/read.
>
> - lets consider someone armed the timer it triggered but no read done
> yet, instead ioctl called and @ticks are set to zero, then call for
> read() and it returns zero to caller not rearming the timer (in
> current patch approach and non-block read)
>
> - in turn if we rearm timer on @ticks = 0 in ioctl this makes it
> close to behaviour of read() function (which in turn look to
> me as a duplication of read() interface).
>
> That said, I'm not sure yet...
What if we prohibit setting non-zero values here? @ticks are set to
zero on timerfd_setup thus there is always a way to create a timer
with fields zeroified. Something like
case TFD_IOC_SET_TICKS: {
u64 ticks;
if (get_user(ticks, (u64 __user *)arg))
return -EFAULT;
if (!ticks)
return -EINVAL;
spin_lock_irq(&ctx->wqh.lock);
if (!timerfd_canceled(ctx)) {
ctx->ticks = ticks;
if (ticks)
wake_up_locked(&ctx->wqh);
else
} else
ret = -ECANCELED;
spin_unlock_irq(&ctx->wqh.lock);
break;
}
?
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