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:
>
> ...
>
> > +#ifdef CONFIG_CHECKPOINT_RESTORE
> > +static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned
> > long arg)
> > +{
> > + struct timerfd_ctx *ctx = file->private_data;
> > + int ret = 0;
> > +
> > + switch (cmd) {
> > + case TFD_IOC_SET_TICKS: {
> > + u64 ticks;
> > +
> > + if (get_user(ticks, (u64 __user *)arg))
> > + return -EFAULT;
> > + spin_lock_irq(&ctx->wqh.lock);
> > + ctx->ticks = ticks;
> > + if (ticks)
> > + wake_up_locked(&ctx->wqh);
>
> 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...
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