From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
rostedt@goodmis.org, John Kacur <jkacur@redhat.com>
Subject: Re: [rfc patch v2] rt,nohz_full: fix nohz_full for PREEMPT_RT_FULL
Date: Mon, 13 Apr 2015 11:41:45 +0200 [thread overview]
Message-ID: <552B8F59.3020708@linutronix.de> (raw)
In-Reply-To: <1428758159.10417.13.camel@gmail.com>
On 04/11/2015 03:15 PM, Mike Galbraith wrote:
> @@ -117,10 +113,8 @@ bool irq_work_queue(struct irq_work *wor
> if (work->flags & IRQ_WORK_HARD_IRQ) {
> if (llist_add(&work->llnode, this_cpu_ptr(&hirq_work_list)))
> arch_irq_work_raise();
> - } else {
> - if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)))
> - arch_irq_work_raise();
> - }
> + } /* for lazy_list we have the timer irq */
>
> If we don't queue work without IRQ_WORK_HARD_IRQ set, how does it run?
We schedule the timer softirq which does the work in the non
IRQ_WORK_HARD_IRQ case.
> Anyway, box did not livelock, nor did it with that bit reverted.
>
>> you could drop the hrtimer hacks. Is this the remaining part all
>> that is
>> required or we shorten the following patch a little more?
>
> rt, nohz_full: fix nohz_full for PREEMPT_RT_FULL
>
> A task being ticked and trying to shut the tick down will fail due
> to having just awakened ksoftirqd, subtract it from nr_running.
thanks.
>
> Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
> ---
> kernel/sched/core.c | 17 ++++++++++++++++-
> kernel/time/tick-sched.c | 5 +++++
> 2 files changed, 21 insertions(+), 1 deletion(-)
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -781,14 +781,29 @@ static inline bool got_nohz_idle_kick(vo
> #endif /* CONFIG_NO_HZ_COMMON */
>
> #ifdef CONFIG_NO_HZ_FULL
> +
> +static int ksoftirqd_running(void)
> +{
> + struct task_struct *softirqd;
> +
> + if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
> + return 0;
> + softirqd = this_cpu_ksoftirqd();
> + if (softirqd && softirqd->on_rq)
> + return 1;
> + return 0;
> +}
> +
> bool sched_can_stop_tick(void)
> {
> /*
> * More than one running task need preemption.
> * nr_running update is assumed to be visible
> * after IPI is sent from wakers.
> + *
> + * NOTE, RT: if ksoftirqd is awake, subtract it.
> */
> - if (this_rq()->nr_running > 1)
> + if (this_rq()->nr_running - ksoftirqd_running() > 1)
> return false;
>
> return true;
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -227,7 +227,12 @@ void __tick_nohz_full_check(void)
>
> static void nohz_full_kick_work_func(struct irq_work *work)
> {
> + unsigned long flags;
> +
> + /* ksoftirqd processes sirqs with interrupts enabled */
> + local_irq_save(flags);
> __tick_nohz_full_check();
> + local_irq_restore(flags);
> }
>
> static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
>
Sebastian
next prev parent reply other threads:[~2015-04-13 9:41 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-16 11:18 [ANNOUNCE] 3.18.7-rt1 Sebastian Andrzej Siewior
2015-02-16 18:13 ` Sebastian Andrzej Siewior
2015-02-16 20:12 ` Richard Cochran
2015-02-16 20:21 ` Steven Rostedt
2015-02-17 8:37 ` Daniel Wagner
2015-02-19 9:36 ` Joakim Hernberg
2015-02-25 13:55 ` Sebastian Andrzej Siewior
2015-02-26 8:48 ` Sebastian Andrzej Siewior
2015-02-27 6:40 ` Daniel Wagner
2015-02-27 7:58 ` Sebastian Andrzej Siewior
2015-02-18 11:21 ` [patch-3.18.7-rt1] sched/context-tracking: fix PREEMPT_LAZY explosions Mike Galbraith
2015-02-18 11:27 ` [rfc patch-3.18.7-rt1] rt/nohz_full: Fix can_stop_full_tick() gripe within softirq Mike Galbraith
2015-02-19 4:50 ` Mike Galbraith
2015-02-19 6:30 ` [patch-3.18.7-rt1] sched/context-tracking: fix PREEMPT_LAZY explosions Mike Galbraith
2015-03-09 13:45 ` Sebastian Andrzej Siewior
2015-03-09 14:36 ` Mike Galbraith
2015-03-09 14:45 ` Sebastian Andrzej Siewior
2015-03-10 9:35 ` Mike Galbraith
2015-03-11 6:18 ` Mike Galbraith
2015-03-12 9:38 ` [rfc patch] rt,nohz_full: fix nohz_full for PREEMPT_RT_FULL Mike Galbraith
2015-03-12 15:09 ` Steven Rostedt
2015-03-13 2:13 ` Mike Galbraith
2015-03-13 3:03 ` Steven Rostedt
2015-03-13 4:53 ` [rfc patch v2] " Mike Galbraith
2015-03-16 20:24 ` Sebastian Andrzej Siewior
2015-03-17 1:53 ` Mike Galbraith
2015-03-17 4:45 ` Mike Galbraith
2015-04-10 14:15 ` Sebastian Andrzej Siewior
2015-04-10 14:24 ` Mike Galbraith
2015-04-10 14:28 ` Mike Galbraith
2015-04-11 13:15 ` Mike Galbraith
2015-04-11 13:36 ` Mike Galbraith
2015-04-11 14:22 ` Mike Galbraith
2015-04-13 9:43 ` Sebastian Andrzej Siewior
2015-04-13 9:41 ` Sebastian Andrzej Siewior [this message]
2015-02-18 14:09 ` [patch-3.18.7-rt1] snd/pcm: fix snd_pcm_stream_lock*() irqs_disabled() splats Mike Galbraith
2015-02-25 14:08 ` Sebastian Andrzej Siewior
2015-02-18 15:05 ` [patch-3.18.7-rt1]sunrpc: make svc_xprt_do_enqueue() use get_cpu_light() Mike Galbraith
2015-02-25 14:14 ` Sebastian Andrzej Siewior
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=552B8F59.3020708@linutronix.de \
--to=bigeasy@linutronix.de \
--cc=jkacur@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rt-users@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=umgwanakikbuti@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).