2020-02-21 21:28:22

by Tom Zanussi

[permalink] [raw]
Subject: [PATCH RT 03/25] sched/deadline: Ensure inactive_timer runs in hardirq context

From: Juri Lelli <[email protected]>

v4.14.170-rt75-rc1 stable review patch.
If anyone has any objections, please let me know.

-----------


[ Upstream commit ba94e7aed7405c58251b1380e6e7d73aa8284b41 ]

SCHED_DEADLINE inactive timer needs to run in hardirq context (as
dl_task_timer already does) on PREEMPT_RT

Change the mode to HRTIMER_MODE_REL_HARD.

[ tglx: Fixed up the start site, so mode debugging works ]

Signed-off-by: Juri Lelli <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
---
kernel/sched/deadline.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index eb68f7fb8a36..7b04e54bea01 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -252,7 +252,7 @@ static void task_non_contending(struct task_struct *p)

dl_se->dl_non_contending = 1;
get_task_struct(p);
- hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL);
+ hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL_HARD);
}

static void task_contending(struct sched_dl_entity *dl_se, int flags)
@@ -1234,7 +1234,7 @@ void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se)
{
struct hrtimer *timer = &dl_se->inactive_timer;

- hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
timer->function = inactive_task_timer;
}

--
2.14.1


Subject: Re: [PATCH RT 03/25] sched/deadline: Ensure inactive_timer runs in hardirq context

On 2020-02-21 15:24:31 [-0600], [email protected] wrote:
> [ Upstream commit ba94e7aed7405c58251b1380e6e7d73aa8284b41 ]
>
> SCHED_DEADLINE inactive timer needs to run in hardirq context (as
> dl_task_timer already does) on PREEMPT_RT

The message says "dl_task_timer already does" but this is not true for
v4.14 as it still runs in softirq context on RT. v4.19 has this either
via
https://lkml.kernel.org/r/[email protected]

or the patch which got merged upstream.

Juri, I guess we want this for v4.14, too?

> Change the mode to HRTIMER_MODE_REL_HARD.
>
> [ tglx: Fixed up the start site, so mode debugging works ]
>
> Signed-off-by: Juri Lelli <[email protected]>
> Signed-off-by: Thomas Gleixner <[email protected]>
> Link: https://lkml.kernel.org/r/[email protected]
> Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
> Signed-off-by: Tom Zanussi <[email protected]>
> ---
> kernel/sched/deadline.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index eb68f7fb8a36..7b04e54bea01 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -252,7 +252,7 @@ static void task_non_contending(struct task_struct *p)
>
> dl_se->dl_non_contending = 1;
> get_task_struct(p);
> - hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL);
> + hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL_HARD);
> }
>
> static void task_contending(struct sched_dl_entity *dl_se, int flags)
> @@ -1234,7 +1234,7 @@ void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se)
> {
> struct hrtimer *timer = &dl_se->inactive_timer;
>
> - hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> + hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
> timer->function = inactive_task_timer;
> }
>

Sebastian

2020-02-25 15:05:06

by Juri Lelli

[permalink] [raw]
Subject: Re: [PATCH RT 03/25] sched/deadline: Ensure inactive_timer runs in hardirq context

Hi,

On 24/02/20 09:33, Sebastian Andrzej Siewior wrote:
> On 2020-02-21 15:24:31 [-0600], [email protected] wrote:
> > [ Upstream commit ba94e7aed7405c58251b1380e6e7d73aa8284b41 ]
> >
> > SCHED_DEADLINE inactive timer needs to run in hardirq context (as
> > dl_task_timer already does) on PREEMPT_RT
>
> The message says "dl_task_timer already does" but this is not true for
> v4.14 as it still runs in softirq context on RT. v4.19 has this either
> via
> https://lkml.kernel.org/r/[email protected]
>
> or the patch which got merged upstream.
>
> Juri, I guess we want this for v4.14, too?

Indeed. v4.14 needs this as well.

Thanks for noticing!

Best,

Juri