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From: Guenter Roeck <linux@roeck-us.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: rjw@rjwysocki.net, bp@alien8.de, x86@kernel.org,
	tony.luck@intel.com, lenb@kernel.org, daniel.lezcano@linaro.org,
	linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
	linux-pm@vger.kernel.org, ulf.hansson@linaro.org,
	paulmck@kernel.org, tglx@linutronix.de,
	naresh.kamboju@linaro.org
Subject: Re: [RFC][PATCH 4/4] acpi: Take over RCU-idle for C3-BM idle
Date: Fri, 25 Sep 2020 08:20:00 -0700	[thread overview]
Message-ID: <20200925152000.GA171076@roeck-us.net> (raw)
In-Reply-To: <20200915103806.479637218@infradead.org>

On Tue, Sep 15, 2020 at 12:32:01PM +0200, Peter Zijlstra wrote:
> The C3 BusMaster idle code takes lock in a number of places, some deep
> inside the ACPI code. Instead of wrapping it all in RCU_NONIDLE, have
> the driver take over RCU-idle duty and avoid flipping RCU state back
> and forth a lot.
> 
> ( by marking 'C3 && bm_check' as RCU_IDLE, we _must_ call enter_bm() for
>   that combination, otherwise we'll loose RCU-idle, this requires
>   shuffling some code around )
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

ia64:defconfig:

ERROR: modpost: "rcu_idle_enter" [drivers/acpi/processor.ko] undefined!
ERROR: modpost: "rcu_idle_exit" [drivers/acpi/processor.ko] undefined!

I realize that this has already been reported more than a week ago, with
no visible reaction. Another problem introduced in the same file, resulting
in

drivers/acpi/processor_idle.c: In function 'lapic_timer_needs_broadcast':
drivers/acpi/processor_idle.c:179:1: warning:
	no return statement in function returning non-void

may cause ia64 boot problems since a non-zero return value will trigger
a function call. AFAICS that is not supposed to happen on ia64.

This makes me wonder - if no one cares about buiding (much less running)
ia64 images with the upstream kernel, is it possibly time to remove it ?

Guenter

  parent reply	other threads:[~2020-09-25 15:20 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-15 10:31 [RFC][PATCH 0/4] Fix up ACPI processor idle vs RCU Peter Zijlstra
2020-09-15 10:31 ` [RFC][PATCH 1/4] acpi: Use CPUIDLE_FLAG_TIMER_STOP Peter Zijlstra
2020-09-15 16:26   ` Rafael J. Wysocki
2020-09-16 15:42     ` peterz
2020-09-16 16:01       ` Borislav Petkov
2020-09-16 17:38         ` Rafael J. Wysocki
2020-09-16 17:38       ` Rafael J. Wysocki
2020-09-22  3:26   ` Guenter Roeck
2020-09-22 19:03     ` Rafael J. Wysocki
2020-09-15 10:31 ` [RFC][PATCH 2/4] acpi: Use CPUIDLE_FLAG_TLB_FLUSHED Peter Zijlstra
2020-09-15 10:32 ` [RFC][PATCH 3/4] cpuidle: Allow cpuidle drivers to take over RCU-idle Peter Zijlstra
2020-09-15 13:20   ` Ulf Hansson
2020-09-15 10:32 ` [RFC][PATCH 4/4] acpi: Take over RCU-idle for C3-BM idle Peter Zijlstra
2020-09-21  9:12   ` Sven Joachim
2020-09-21 10:37     ` [PATCH] rcu/tree: Export rcu_idle_{enter,exit} to module Borislav Petkov
2020-09-21 12:15       ` Rafael J. Wysocki
2020-09-21 13:32       ` Paul E. McKenney
2020-09-21 13:38         ` Rafael J. Wysocki
2020-09-25 15:20   ` Guenter Roeck [this message]
2020-09-25 15:24     ` [RFC][PATCH 4/4] acpi: Take over RCU-idle for C3-BM idle Rafael J. Wysocki
2020-09-25 15:29     ` Paul E. McKenney
2020-09-15 18:31 ` [RFC][PATCH 0/4] Fix up ACPI processor idle vs RCU Borislav Petkov

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