UML time-travel warning from __run_timers

[Johannes Berg]

On Sat, 2022-04-02 at 16:09 +0200, Johannes Berg wrote:
> 
> (I put a WARN_ON into get_timer_cpu_base() and get_timer_this_cpu_base()
> in the if, and it never triggered; I guess my config has something that
> creates a deferrable timer, so it didn't trigger, but I didn't check
> that now.)
> 

OK, so FWIW, I checked that now, and I have e.g. CONFIG_WQ_WATCHDOG
enabled, which makes a deferrable timer:

static void wq_watchdog_init(void)
{
        timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);


but I think a bunch of other (networking) things too that end up using a
TIMER_DEFERRABLE timer, via workqueues.

But maybe this would also happen if it was used just a single time,
since the timer would run & go away, leaving base->next_expiry never to
change again? But the WQ watchdog and also neigh_managed_work() are
periodic.

johannes