Re: WARNING in hrtimer_forward

[Dmitry Vyukov]

On Mon, Sep 28, 2020 at 8:36 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
> On Tue, Sep 29 2020 at 01:11, Hillf Danton wrote:
> > On Mon, 28 Sep 2020 18:13:42 +0200 Thomas Gleixner wrote:
> >> So the timer was armed at some point and then the expiry which does the
> >> forward races with the ioctl which starts the timer. Lack of
> >> serialization or such ...
> >
> > To make syzbot happy, s/hrtimer_is_queued/hrtimer_active/ can close
> > that race but this warning looks benign.
>
> Why only make sysbot happy? It's clearly an issue and the warning is not
> benign simply because forwarding a queued timer is an absolute NONO.
> timers (both timer_list and hrtimer) need external synchronization.

Oh, Thomas, it's so nice to hear this interpretation of things among
all the cases where people only fixing tools and making them happy :)
Don't make my tools happy! They don't need that! :)