On Thu, 14 Jun 2018 22:55:56 +0100 Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx> wrote: > On Mon, 2018-05-28 at 12:02 +0200, Greg Kroah-Hartman wrote: > > 4.4-stable review patch. If anyone has any objections, please let me know. > > > > ------------------ > > > > From: Davidlohr Bueso <dave@xxxxxxxxxxxx> > > > > [ Upstream commit d29a20645d5e929aa7e8616f28e5d8e1c49263ec ] > > > > While running rt-tests' pi_stress program I got the following splat: > > > > rq->clock_update_flags < RQCF_ACT_SKIP > > WARNING: CPU: 27 PID: 0 at kernel/sched/sched.h:960 assert_clock_updated.isra.38.part.39+0x13/0x20 > > > > [...] > > > > <IRQ> > > enqueue_top_rt_rq+0xf4/0x150 > > ? cpufreq_dbs_governor_start+0x170/0x170 > > sched_rt_rq_enqueue+0x65/0x80 > > sched_rt_period_timer+0x156/0x360 > > ? sched_rt_rq_enqueue+0x80/0x80 > > __hrtimer_run_queues+0xfa/0x260 > > hrtimer_interrupt+0xcb/0x220 > > smp_apic_timer_interrupt+0x62/0x120 > > apic_timer_interrupt+0xf/0x20 > > </IRQ> > > > > [...] > > > > do_idle+0x183/0x1e0 > > cpu_startup_entry+0x5f/0x70 > > start_secondary+0x192/0x1d0 > > secondary_startup_64+0xa5/0xb0 > > > > We can get rid of it be the "traditional" means of adding an > > update_rq_clock() call after acquiring the rq->lock in > > do_sched_rt_period_timer(). > > > > The case for the RT task throttling (which this workload also hits) > > can be ignored in that the skip_update call is actually bogus and > > quite the contrary (the request bits are removed/reverted). > > > > By setting RQCF_UPDATED we really don't care if the skip is happening > > or not and will therefore make the assert_clock_updated() check happy. > > There is no such flag or assertion in 4.4 or 4.9, so does this change > still make sense there? I believe the assert was added to catch bugs like this. Although the change log is a bit ambiguous in if it is fixing an actual miss update, or if it is just quieting a false positive. Davidlohr? -- Steve > > Ben. > > > Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx> > > Reviewed-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> > > Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > > Cc: Mike Galbraith <efault@xxxxxx> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: dave@xxxxxxxxxxxx > > Cc: linux-kernel@xxxxxxxxxxxxxxx > > Cc: rostedt@xxxxxxxxxxx > > Link: http://lkml.kernel.org/r/20180402164954.16255-1-dave@xxxxxxxxxxxx > > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> > > Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > --- > > kernel/sched/rt.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > --- a/kernel/sched/rt.c > > +++ b/kernel/sched/rt.c > > @@ -822,6 +822,8 @@ static int do_sched_rt_period_timer(stru > > struct rq *rq = rq_of_rt_rq(rt_rq); > > > > raw_spin_lock(&rq->lock); > > + update_rq_clock(rq); > > + > > if (rt_rq->rt_time) { > > u64 runtime; > > > > > > > >
