From: Nicolas Pitre <nicolas.pitre@linaro.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, tglx@linutronix.de, luto@amacapital.net,
daniel.lezcano@linaro.org, umgwanakikbuti@gmail.com,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 7/8] sched,idle: Delay clearing the polling bit
Date: Sun, 13 Apr 2014 17:51:03 -0400 (EDT) [thread overview]
Message-ID: <alpine.LFD.2.11.1404131749430.980@knanqh.ubzr> (raw)
In-Reply-To: <20140411135218.546673774@infradead.org>
On Fri, 11 Apr 2014, Peter Zijlstra wrote:
> With the generic idle functions assuming !polling we should only clear
> the polling bit at the very last opportunity in order to avoid
> spurious IPIs.
>
> Ideally we'd flip the default to polling, but that means auditing all
> arch idle functions.
>
> Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
> ---
> kernel/sched/idle.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -78,12 +78,10 @@ static int cpuidle_idle_call(void)
>
> /*
> * Check if the idle task must be rescheduled. If it is the
> - * case, exit the function after re-enabling the local irq and
> - * set again the polling flag
> + * case, exit the function after re-enabling the local irq.
> */
> - if (current_clr_polling_and_test()) {
> + if (need_resched()) {
> local_irq_enable();
> - __current_set_polling();
> return 0;
> }
>
> @@ -127,7 +125,7 @@ static int cpuidle_idle_call(void)
> broadcast = !!(drv->states[next_state].flags &
> CPUIDLE_FLAG_TIMER_STOP);
>
> - if (broadcast)
> + if (broadcast) {
> /*
> * Tell the time framework to switch
> * to a broadcast timer because our
> @@ -139,6 +137,7 @@ static int cpuidle_idle_call(void)
> ret = clockevents_notify(
> CLOCK_EVT_NOTIFY_BROADCAST_ENTER,
> &dev->cpu);
> + }
>
> if (!ret) {
> trace_cpu_idle_rcuidle(next_state, dev->cpu);
> @@ -175,8 +174,12 @@ static int cpuidle_idle_call(void)
> * We can't use the cpuidle framework, let's use the default
> * idle routine
> */
> - if (ret)
> - arch_cpu_idle();
> + if (ret) {
> + if (!current_clr_polling_and_test())
> + arch_cpu_idle();
> + else
> + local_irq_enable();
> + }
>
> __current_set_polling();
>
>
>
next prev parent reply other threads:[~2014-04-13 21:51 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-11 13:42 [RFC][PATCH 0/8] sched,idle: need resched polling rework Peter Zijlstra
2014-04-11 13:42 ` [RFC][PATCH 1/8] sched,idle,alpha: Switch from TS_POLLING to TIF_POLLING_NRFLAG Peter Zijlstra
2014-04-11 14:38 ` Richard Henderson
2014-04-11 13:42 ` [RFC][PATCH 2/8] sched,idle,tile: " Peter Zijlstra
2014-04-11 15:15 ` Chris Metcalf
2014-04-11 15:30 ` Peter Zijlstra
2014-04-11 13:42 ` [RFC][PATCH 3/8] sched,idle,ia64: " Peter Zijlstra
2014-04-11 13:42 ` [RFC][PATCH 4/8] sched,idle,x86: " Peter Zijlstra
2014-04-11 13:42 ` [RFC][PATCH 5/8] sched,idle: Remove TS_POLLING support Peter Zijlstra
2014-04-11 13:42 ` [RFC][PATCH 6/8] sched,idle: Avoid spurious wakeup IPIs Peter Zijlstra
2014-04-13 21:41 ` Nicolas Pitre
2014-05-09 13:37 ` James Hogan
2014-05-09 14:15 ` Peter Zijlstra
2014-05-09 14:40 ` Catalin Marinas
2014-05-09 14:50 ` Peter Zijlstra
2014-05-09 14:57 ` Catalin Marinas
2014-05-09 17:02 ` Peter Zijlstra
2014-05-09 17:06 ` Peter Zijlstra
2014-05-09 17:09 ` Catalin Marinas
2014-05-09 17:20 ` Peter Zijlstra
2014-05-19 12:54 ` [tip:sched/arch] arm64: Remove TIF_POLLING_NRFLAG tip-bot for Peter Zijlstra
2014-05-22 12:26 ` [tip:sched/core] " tip-bot for Peter Zijlstra
2014-05-09 14:51 ` [RFC][PATCH 6/8] sched,idle: Avoid spurious wakeup IPIs James Hogan
2014-05-15 9:17 ` James Hogan
2014-05-19 12:54 ` [tip:sched/arch] metag: Remove TIF_POLLING_NRFLAG tip-bot for James Hogan
2014-05-22 12:26 ` [tip:sched/core] " tip-bot for James Hogan
2014-04-11 13:42 ` [RFC][PATCH 7/8] sched,idle: Delay clearing the polling bit Peter Zijlstra
2014-04-13 21:51 ` Nicolas Pitre [this message]
2014-04-11 13:42 ` [RFC][PATCH 8/8] sched,idle: Reflow cpuidle_idle_call() Peter Zijlstra
2014-04-13 21:36 ` Nicolas Pitre
2014-04-14 8:59 ` Peter Zijlstra
2014-04-14 9:25 ` Peter Zijlstra
2014-04-14 13:55 ` Nicolas Pitre
2014-04-11 15:00 ` [RFC][PATCH 0/8] sched,idle: need resched polling rework Andy Lutomirski
2014-04-11 15:14 ` Peter Zijlstra
2014-05-22 12:58 ` Peter Zijlstra
2014-05-22 13:09 ` Peter Zijlstra
2014-05-29 0:01 ` Andy Lutomirski
2014-05-29 6:48 ` Peter Zijlstra
2014-06-03 6:40 ` Andy Lutomirski
2014-06-03 6:51 ` Peter Zijlstra
2014-06-03 10:43 ` Peter Zijlstra
2014-06-03 14:02 ` Peter Zijlstra
2014-06-03 16:05 ` Andy Lutomirski
2014-06-03 16:19 ` Peter Zijlstra
2014-06-03 16:52 ` Andy Lutomirski
2014-06-03 17:00 ` Peter Zijlstra
2014-06-03 18:28 ` Peter Zijlstra
2014-06-03 18:44 ` Andy Lutomirski
2014-06-03 20:07 ` Andy Lutomirski
2014-04-12 8:35 ` Mike Galbraith
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