lkml.org 
[lkml]   [2018]   [Jun]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 4.4 173/268] sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
From
Date
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@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.

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@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
> @@ -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

\
 
 \ /
  Last update: 2018-06-14 23:57    [W:1.052 / U:4.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site