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? 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; > > > > -- Ben Hutchings, Software Developer Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom
