4.9-stable review patch. If anyone has any objections, please let me know.
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From: Davidlohr Bueso dave@stgolabs.net
[ 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.
Signed-off-by: Davidlohr Bueso dbueso@suse.de Reviewed-by: Matt Fleming matt@codeblueprint.co.uk Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Mike Galbraith efault@gmx.de Cc: Thomas Gleixner tglx@linutronix.de Cc: dave@stgolabs.net Cc: linux-kernel@vger.kernel.org Cc: rostedt@goodmis.org Link: http://lkml.kernel.org/r/20180402164954.16255-1-dave@stgolabs.net Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/sched/rt.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -830,6 +830,8 @@ 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;