On Fri, Mar 05, 2021 at 02:41:11PM +0100, Frederic Weisbecker wrote: > On Wed, Mar 03, 2021 at 11:49:45AM -0800, Paul E. McKenney wrote: > > Hello, Frederic! > > > > I don't see the following commit in mainline, but figured I should > > check with you guys to see if the problem got solved in some other way. > > Unless I hear otherwise, I will continue to carry this patch in -rcu > > and will send it along for the v5.13 merge window. > > I have it included in a nohz series I'm about to post but since RCU is the > motivation behind doing this, it's fine if you carry it.
Actually, please feel free to run this up the normal nohz path. I will remove my version once yours hits mainline, as I did with the others. I was just curious. ;-) Thanx, Paul > I've just modified it a bit after a review from Peter: > > --- > >From 7876725b8631147967bb9e65158ef1cb2bb94372 Mon Sep 17 00:00:00 2001 > From: Frederic Weisbecker <frede...@kernel.org> > Date: Fri, 8 Jan 2021 13:50:12 +0100 > Subject: [PATCH] timer: Report ignored local enqueue in nohz mode > > Enqueuing a local timer after the tick has been stopped will result in > the timer being ignored until the next random interrupt. > > Perform sanity checks to report these situations. > > Signed-off-by: Frederic Weisbecker <frede...@kernel.org> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Ingo Molnar<mi...@kernel.org> > Cc: Paul E. McKenney <paul...@kernel.org> > Cc: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > --- > kernel/sched/core.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index ca2bb629595f..24552911f92b 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -674,6 +674,22 @@ int get_nohz_timer_target(void) > return cpu; > } > > +/* Make sure the timer won't be ignored in dynticks-idle case */ > +static void wake_idle_assert_possible(void) > +{ > +#ifdef CONFIG_SCHED_DEBUG > + /* > + * Timers are re-evaluated after idle IRQs. In case of softirq, > + * we assume IRQ tail. Ksoftirqd shouldn't reach here as the > + * timer base wouldn't be idle. And inline softirq processing > + * after a call to local_bh_enable() within idle loop sound too > + * fun to be considered here. > + */ > + WARN_ONCE(in_task(), > + "Late timer enqueue may be ignored\n"); > +#endif > +} > + > /* > * When add_timer_on() enqueues a timer into the timer wheel of an > * idle CPU then this timer might expire before the next timer event > @@ -688,8 +704,10 @@ static void wake_up_idle_cpu(int cpu) > { > struct rq *rq = cpu_rq(cpu); > > - if (cpu == smp_processor_id()) > + if (cpu == smp_processor_id()) { > + wake_idle_assert_possible(); > return; > + } > > if (set_nr_and_not_polling(rq->idle)) > smp_send_reschedule(cpu); > -- > 2.25.1 >