Re: [PATCH 4.4 173/268] sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
On Thu, 14 Jun 2018, Steven Rostedt wrote: 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? It fixes an update, not a false positive. Thanks, Davidlohr
Re: [PATCH 4.4 173/268] sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
On Thu, 14 Jun 2018, Steven Rostedt wrote: 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? It fixes an update, not a false positive. Thanks, Davidlohr
Re: [PATCH 4.4 173/268] sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
On Thu, 14 Jun 2018 22:55:56 +0100
Ben Hutchings 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
> >
> > [ 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
> >
> > [...]
> >
> >
> > 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
> >
> >
> > [...]
> >
> > 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
> > Reviewed-by: Matt Fleming
> > Acked-by: Peter Zijlstra (Intel)
> > Cc: Linus Torvalds
> > Cc: Mike Galbraith
> > Cc: Thomas Gleixner
> > Cc: d...@stgolabs.net
> > Cc: linux-kernel@vger.kernel.org
> > Cc: rost...@goodmis.org
> > Link: http://lkml.kernel.org/r/20180402164954.16255-1-d...@stgolabs.net
> > Signed-off-by: Ingo Molnar
> > Signed-off-by: Sasha Levin
> > Signed-off-by: Greg Kroah-Hartman
> > ---
> > 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(>lock);
> > + update_rq_clock(rq);
> > +
> > if (rt_rq->rt_time) {
> > u64 runtime;
> >
> >
> >
> >
Re: [PATCH 4.4 173/268] sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
On Thu, 14 Jun 2018 22:55:56 +0100
Ben Hutchings 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
> >
> > [ 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
> >
> > [...]
> >
> >
> > 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
> >
> >
> > [...]
> >
> > 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
> > Reviewed-by: Matt Fleming
> > Acked-by: Peter Zijlstra (Intel)
> > Cc: Linus Torvalds
> > Cc: Mike Galbraith
> > Cc: Thomas Gleixner
> > Cc: d...@stgolabs.net
> > Cc: linux-kernel@vger.kernel.org
> > Cc: rost...@goodmis.org
> > Link: http://lkml.kernel.org/r/20180402164954.16255-1-d...@stgolabs.net
> > Signed-off-by: Ingo Molnar
> > Signed-off-by: Sasha Levin
> > Signed-off-by: Greg Kroah-Hartman
> > ---
> > 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(>lock);
> > + update_rq_clock(rq);
> > +
> > if (rt_rq->rt_time) {
> > u64 runtime;
> >
> >
> >
> >
Re: [PATCH 4.4 173/268] sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
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
>
> [ 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
>
> [...]
>
>
> 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
>
>
> [...]
>
> 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
> Reviewed-by: Matt Fleming
> Acked-by: Peter Zijlstra (Intel)
> Cc: Linus Torvalds
> Cc: Mike Galbraith
> Cc: Thomas Gleixner
> Cc: d...@stgolabs.net
> Cc: linux-kernel@vger.kernel.org
> Cc: rost...@goodmis.org
> Link: http://lkml.kernel.org/r/20180402164954.16255-1-d...@stgolabs.net
> Signed-off-by: Ingo Molnar
> Signed-off-by: Sasha Levin
> Signed-off-by: Greg Kroah-Hartman
> ---
> 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(>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
Re: [PATCH 4.4 173/268] sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
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
>
> [ 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
>
> [...]
>
>
> 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
>
>
> [...]
>
> 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
> Reviewed-by: Matt Fleming
> Acked-by: Peter Zijlstra (Intel)
> Cc: Linus Torvalds
> Cc: Mike Galbraith
> Cc: Thomas Gleixner
> Cc: d...@stgolabs.net
> Cc: linux-kernel@vger.kernel.org
> Cc: rost...@goodmis.org
> Link: http://lkml.kernel.org/r/20180402164954.16255-1-d...@stgolabs.net
> Signed-off-by: Ingo Molnar
> Signed-off-by: Sasha Levin
> Signed-off-by: Greg Kroah-Hartman
> ---
> 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(>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
