From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
stable@vger.kernel.org, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 2/5] rcu/nocb: Perform deferred wake up before last idle's need_resched() check
Date: Mon, 8 Feb 2021 15:53:08 +0100 [thread overview]
Message-ID: <20210208145308.GC3969@lothringen> (raw)
In-Reply-To: <YCFOnhwQAjMMkwGN@hirez.programming.kicks-ass.net>
On Mon, Feb 08, 2021 at 03:45:50PM +0100, Peter Zijlstra wrote:
> On Mon, Feb 01, 2021 at 12:05:45AM +0100, Frederic Weisbecker wrote:
>
> > diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> > index 305727ea0677..b601a3aa2152 100644
> > --- a/kernel/sched/idle.c
> > +++ b/kernel/sched/idle.c
> > @@ -55,6 +55,7 @@ __setup("hlt", cpu_idle_nopoll_setup);
> > static noinline int __cpuidle cpu_idle_poll(void)
> > {
> > trace_cpu_idle(0, smp_processor_id());
> > + rcu_nocb_flush_deferred_wakeup();
> > stop_critical_timings();
> > rcu_idle_enter();
> > local_irq_enable();
> > @@ -173,6 +174,8 @@ static void cpuidle_idle_call(void)
> > struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
> > int next_state, entered_state;
> >
> > + rcu_nocb_flush_deferred_wakeup();
> > +
> > /*
> > * Check if the idle task must be rescheduled. If it is the
> > * case, exit the function after re-enabling the local irq.
>
> Ok if I do this instead?
>
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -55,7 +55,6 @@ __setup("hlt", cpu_idle_nopoll_setup);
> static noinline int __cpuidle cpu_idle_poll(void)
> {
> trace_cpu_idle(0, smp_processor_id());
> - rcu_nocb_flush_deferred_wakeup();
> stop_critical_timings();
> rcu_idle_enter();
> local_irq_enable();
> @@ -174,8 +173,6 @@ static void cpuidle_idle_call(void)
> struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
> int next_state, entered_state;
>
> - rcu_nocb_flush_deferred_wakeup();
> -
> /*
> * Check if the idle task must be rescheduled. If it is the
> * case, exit the function after re-enabling the local irq.
> @@ -288,6 +285,7 @@ static void do_idle(void)
> }
>
> arch_cpu_idle_enter();
> + rcu_nocb_flush_deferred_wakeup();
>
> /*
> * In poll mode we reenable interrupts and spin. Also if we
Right, I think that should work. Nothing should call_rcu() before the
need_resched() call. And if it does, we still have the nocb_timer to do
the deferred wakeup in the worst case.
Thanks.
next prev parent reply other threads:[~2021-02-08 14:55 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-31 23:05 [PATCH 0/5] rcu/sched: Fix ignored rescheduling after rcu_eqs_enter() v4 Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 1/5] rcu: Pull deferred rcuog wake up to rcu_eqs_enter() callers Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 2/5] rcu/nocb: Perform deferred wake up before last idle's need_resched() check Frederic Weisbecker
2021-02-08 14:45 ` Peter Zijlstra
2021-02-08 14:53 ` Frederic Weisbecker [this message]
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 3/5] rcu/nocb: Trigger self-IPI on late deferred wake up before user resume Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 4/5] entry: Explicitly flush pending rcuog wakeup before last rescheduling point Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 5/5] entry/kvm: " Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
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