From: Thomas Gleixner <tglx@linutronix.de>
To: Rich Felker <dalias@libc.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-sh@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v7 2/2] clocksource: add J-Core timer/clocksource driver
Date: Sat, 8 Oct 2016 13:32:06 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1610081312190.5222@nanos> (raw)
In-Reply-To: <20161008013210.GX19318@brightrain.aerifal.cx>
On Fri, 7 Oct 2016, Rich Felker wrote:
>
> If I'm not mistaken, the bug is in tick_nohz_restart. According to the
I think you are mistaken. Let's look at CPU0 only:
<idle>-0 [000] d... 150.829698: __tick_nohz_idle_enter: can stop idle tick
<idle>-0 [000] d... 150.829774: __tick_nohz_idle_enter: entering stop_sched_tick
<idle>-0 [000] d... 150.830001: tick_stop: success=1 dependency=NONE
<idle>-0 [000] d... 150.830127: hrtimer_cancel: hrtimer=109e949c
<idle>-0 [000] d... 150.830380: jcore_pit_set_next_event: pit 109eccb0 0 set delta 82124660 en=4410000 cntr=75 throt=82124660
<idle>-0 [000] d... 150.830498: hrtimer_start: hrtimer=109e949c function=tick_sched_timer expires=150840000000 softexpires=150840000000
<idle>-0 [000] d... 150.830720: jcore_pit_set_next_event: pit 109eccb0 0 set delta 539823 en=4410000 cntr=34 throt=539823
Tick is programmed to fire at 150.84
<idle>-0 [000] d... 150.830822: __tick_nohz_idle_enter: returning from stop_sched_tick
<idle>-0 [000] d... 150.830940: rcu_dyntick: Start 140000000000000 0
<idle>-0 [000] d... 150.831072: rcu_dyntick: End 0 1
<idle>-0 [000] d... 150.831165: cpu_idle: state=0 cpu_id=0
<idle>-0 [000] d... 150.831269: rcu_dyntick: Start 1 0
<idle>-0 [000] .... 150.831368: cpu_startup_entry: enabled irqs, spinning
CPU spins and waits for an interrupt to happen
<idle>-0 [000] d... 150.841530: rcu_dyntick: End 0 1
Dropping out of the spin about the time we expect the PIT interrupt to
fire. And an interrupt is the reason why we drop out because the 'need
resched' flag is not set and we end up in:
<idle>-0 [000] d.s. 150.841724: tick_irq_enter: update jiffies via irq
which is called from irq_enter()
<idle>-0 [000] d.s. 150.841918: tick_do_update_jiffies64: finished do_timer(1)
<idle>-0 [000] d.s. 150.842348: tick_do_update_jiffies64: finished updating jiffies
So here we would expect:
irq_handler_entry: irq=16 name=jcore_pit
...
irq_handler_exit .....
or any other interrupt being invoked. But we see this here:
<idle>-0 [000] d... 150.842603: __tick_nohz_idle_enter: can stop idle tick
And that's just wrong.
Now looking at CPU1 at the same time:
<idle>-0 [001] d.h. 150.841829: irq_handler_entry: irq=16 name=jcore_ <idle>-0 [001] d.h. 150.842054: hrtimer_cancel: hrtimer=109f449c
<idle>-0 [001] d.h. 150.842218: hrtimer_expire_entry: hrtimer=109f449c function=tick_sched_timer now=150840579940
So there the PIT interrupt enters and runs the interrupt handler.
Now looking deeper at the PIT interrupts:
kworker/0:1-208 [000] d.h. 150.641822: irq_handler_entry: irq=16 name=jcore_pit
kworker/0:1-208 [000] d.h. 150.644928: irq_handler_exit: irq=16 ret=handled
<idle>-0 [001] dnh. 150.645370: irq_handler_entry: irq=16 name=jcore_pit
<idle>-0 [001] dnh. 150.647444: irq_handler_exit: irq=16 ret=handled
Both CPUs have the same interrupt number for their per cpu PIT interrupt.
IIRC you said earlier when the percpu interrupt discussion happened, that
your per cpu PITs have distinct interrupt numbers, but that does not seem
the case here.
That's where you have to dig.
Thanks,
tglx
next prev parent reply other threads:[~2016-10-08 11:35 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-24 5:07 [PATCH v7 0/2] J-Core timer support Rich Felker
2016-09-24 5:07 ` [PATCH v7 2/2] clocksource: add J-Core timer/clocksource driver Rich Felker
2016-09-26 21:07 ` Rich Felker
2016-09-26 21:27 ` Daniel Lezcano
2016-09-26 22:23 ` Rich Felker
2016-09-26 23:55 ` Thomas Gleixner
2016-09-27 0:42 ` Rich Felker
2016-09-27 22:08 ` Rich Felker
2016-09-30 13:15 ` Thomas Gleixner
2016-09-30 13:48 ` Paul E. McKenney
2016-10-01 17:05 ` Rich Felker
2016-10-01 17:58 ` Paul E. McKenney
2016-10-02 0:00 ` Rich Felker
2016-10-02 3:59 ` Rich Felker
2016-10-02 5:59 ` Paul E. McKenney
2016-10-02 6:30 ` Paul E. McKenney
2016-10-08 1:32 ` Rich Felker
2016-10-08 11:32 ` Thomas Gleixner [this message]
2016-10-08 16:26 ` Rich Felker
2016-10-08 17:03 ` Thomas Gleixner
2016-10-09 1:28 ` Rich Felker
2016-10-09 9:14 ` Thomas Gleixner
2016-10-09 14:35 ` Rich Felker
2016-10-03 22:10 ` Rich Felker
2016-10-04 7:06 ` Paul E. McKenney
2016-10-04 20:58 ` Rich Felker
2016-10-04 21:14 ` Paul E. McKenney
2016-10-04 21:48 ` Rich Felker
2016-10-05 12:41 ` Paul E. McKenney
2016-09-24 5:07 ` [PATCH v7 1/2] of: add J-Core timer bindings Rich Felker
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=alpine.DEB.2.20.1610081312190.5222@nanos \
--to=tglx@linutronix.de \
--cc=dalias@libc.org \
--cc=daniel.lezcano@linaro.org \
--cc=devicetree@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-sh@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=robh+dt@kernel.org \
/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).