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From: tip-bot for Thomas Gleixner <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: tglx@linutronix.de, bp@alien8.de, mingo@kernel.org,
	torvalds@linux-foundation.org, rafael.j.wysocki@intel.com,
	linux-kernel@vger.kernel.org, peterz@infradead.org,
	hpa@zytor.com
Subject: [tip:timers/core] ACPI/PAD: Remove the local APIC nonsense
Date: Fri, 3 Apr 2015 01:21:40 -0700	[thread overview]
Message-ID: <tip-3ff70551a942b4c1d3c2e96e31a5c6e369a6d0be@git.kernel.org> (raw)
In-Reply-To: <1887788.RObRuI4tSv@vostro.rjw.lan>

Commit-ID:  3ff70551a942b4c1d3c2e96e31a5c6e369a6d0be
Gitweb:     http://git.kernel.org/tip/3ff70551a942b4c1d3c2e96e31a5c6e369a6d0be
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Fri, 3 Apr 2015 01:46:34 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 3 Apr 2015 08:44:31 +0200

ACPI/PAD: Remove the local APIC nonsense

While looking through the (ab)use of the clockevents_notify()
function I stumbled over the following gem in the acpi_pad code:

  if (lapic_detected_unstable && !lapic_marked_unstable) {
     /* LAPIC could halt in idle, so notify users */
     for_each_online_cpu(i)
       clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ON, &i);
     lapic_marked_unstable = 1;
  }

This code calls on the cpu which detects the lapic unstable
condition first clockevents_notify() to tell the core code that
the broadcast should be enabled on all online cpus. Brilliant
stuff that as it notifies the core code a num_online_cpus()
times that the broadcast should be enabled on the current cpu.

This probably has never been noticed because that code got never
tested with NOHZ=n and HIGHRES_TIMER=n or it just worked by
chance because one of the other mechanisms told the core in the
right way that the local apic timer is wreckaged.

Sigh, this is:

 - The 4th incarnation of idle drivers which has their own mechanism
   to detect and deal with X86_FEATURE_ARAT.

 - The 2nd incarnation of fake idle mechanisms with a different set of
   brainmelting bugs.

 - Has been merged against an explicit NAK of the scheduler
   maintainer with the promise to improve it over time.

 - Another example of featuritis driven trainwreck engineering.

 - Another pointless waste of my time.

Fix this nonsense by removing that lapic detection and
notification logic and simply call into the clockevents code
unconditonally. The ARAT feature is marked in the lapic
clockevent already so the core code will just ignore the
requests and return.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1887788.RObRuI4tSv@vostro.rjw.lan
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 drivers/acpi/acpi_pad.c | 26 +++++---------------------
 1 file changed, 5 insertions(+), 21 deletions(-)

diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index c7b105c..1686e9f 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -41,8 +41,6 @@ static unsigned long power_saving_mwait_eax;
 
 static unsigned char tsc_detected_unstable;
 static unsigned char tsc_marked_unstable;
-static unsigned char lapic_detected_unstable;
-static unsigned char lapic_marked_unstable;
 
 static void power_saving_mwait_init(void)
 {
@@ -82,13 +80,10 @@ static void power_saving_mwait_init(void)
 		 */
 		if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 			tsc_detected_unstable = 1;
-		if (!boot_cpu_has(X86_FEATURE_ARAT))
-			lapic_detected_unstable = 1;
 		break;
 	default:
-		/* TSC & LAPIC could halt in idle */
+		/* TSC could halt in idle */
 		tsc_detected_unstable = 1;
-		lapic_detected_unstable = 1;
 	}
 #endif
 }
@@ -177,28 +172,17 @@ static int power_saving_thread(void *data)
 				mark_tsc_unstable("TSC halts in idle");
 				tsc_marked_unstable = 1;
 			}
-			if (lapic_detected_unstable && !lapic_marked_unstable) {
-				int i;
-				/* LAPIC could halt in idle, so notify users */
-				for_each_online_cpu(i)
-					clockevents_notify(
-						CLOCK_EVT_NOTIFY_BROADCAST_ON,
-						&i);
-				lapic_marked_unstable = 1;
-			}
+			clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ON, &cpu);
+
 			local_irq_disable();
 			cpu = smp_processor_id();
-			if (lapic_marked_unstable)
-				clockevents_notify(
-					CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
+			clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
 			stop_critical_timings();
 
 			mwait_idle_with_hints(power_saving_mwait_eax, 1);
 
 			start_critical_timings();
-			if (lapic_marked_unstable)
-				clockevents_notify(
-					CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
+			clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
 			local_irq_enable();
 
 			if (time_before(expire_time, jiffies)) {

  reply	other threads:[~2015-04-03  8:22 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-01 22:02 [PATCH 00/20] clockevents_notify() removal Rafael J. Wysocki
2015-04-01 22:03 ` [PATCH 01/20] clockevents: Provide explicit broadcast control functions Rafael J. Wysocki
2015-04-01 22:04 ` [PATCH 02/20] x86, amd_idle: Use explicit broadcast control function Rafael J. Wysocki
2015-04-01 22:05 ` [PATCH 03/20] ACPI / PAD: " Rafael J. Wysocki
2015-04-01 22:06 ` [PATCH 04/20] ACPI / processor: " Rafael J. Wysocki
2015-04-01 22:07 ` [PATCH 05/20] cpuidle: " Rafael J. Wysocki
2015-04-01 22:09 ` [PATCH 06/20] intel_idle: " Rafael J. Wysocki
2015-04-01 22:10 ` [PATCH 07/20] ARM: OMAP: " Rafael J. Wysocki
2015-04-01 22:11 ` [PATCH 08/20] clockevents: Remove the broadcast control leftovers Rafael J. Wysocki
2015-04-01 22:13 ` [PATCH 09/20] clockevents: Provide explicit broadcast oneshot control functions Rafael J. Wysocki
2015-04-01 22:15 ` [PATCH 10/20] x86, amd_idle: Use " Rafael J. Wysocki
2015-04-01 22:16 ` [PATCH 11/20] ACPI / PAD: Use explicit broadcast oneshot control function Rafael J. Wysocki
2015-04-01 22:17 ` [PATCH 12/20] ACPI / processor: Use explicit broadcast controll function Rafael J. Wysocki
2015-04-01 22:20 ` [PATCH 13/20] intel_idle: Use explicit broadcast oneshot control function Rafael J. Wysocki
2015-04-01 22:20 ` [PATCH 14/20] ARM: OMAP: " Rafael J. Wysocki
2015-04-01 22:21 ` [PATCH 15/20] ARM: tegra: " Rafael J. Wysocki
2015-04-01 22:22 ` [PATCH 16/20] sched/idle: " Rafael J. Wysocki
2015-04-28 10:11   ` Linus Walleij
2015-04-28 10:17     ` Sudeep Holla
2015-04-28 10:34     ` Daniel Lezcano
2015-04-28 10:42       ` Sudeep Holla
2015-04-28 12:19         ` Rafael J. Wysocki
2015-04-28 12:37           ` Linus Walleij
2015-04-28 13:31             ` Rafael J. Wysocki
2015-04-28 13:37               ` Rafael J. Wysocki
2015-04-28 14:14                 ` Rafael J. Wysocki
2015-04-28 13:58                   ` Sudeep Holla
2015-04-29  0:50                     ` Rafael J. Wysocki
2015-04-29  1:04                       ` Rafael J. Wysocki
2015-04-29  7:10                         ` Linus Walleij
2015-04-29  8:57                         ` Peter Zijlstra
2015-04-29  9:44                         ` Daniel Lezcano
2015-04-29  9:50                         ` Sudeep Holla
2015-04-29 14:07                           ` [PATCH][Fix] cpuidle: Run tick_broadcast_exit() with disabled interrupts Rafael J. Wysocki
2015-04-30  3:47                             ` Preeti U Murthy
2015-04-30 20:12                             ` Nicolas Pitre
2015-04-30 22:10                               ` Rafael J. Wysocki
2015-04-30  3:45                         ` [PATCH 16/20] sched/idle: Use explicit broadcast oneshot control function Preeti U Murthy
2015-04-28 13:04           ` Sudeep Holla
2015-04-01 22:23 ` [PATCH 17/20] clockevents: Remove broadcast oneshot control leftovers Rafael J. Wysocki
2015-04-01 22:24 ` [PATCH 18/20] clockevents: Make tick handover explicit Rafael J. Wysocki
2015-04-01 22:25 ` [PATCH 19/20] clockevents: Cleanup dead cpu explicitely Rafael J. Wysocki
2015-04-01 22:26 ` [PATCH 20/20] timekeeping: Get rid of stale comment Rafael J. Wysocki
2015-04-01 23:57   ` John Stultz
2015-04-02 12:39 ` [PATCH 00/20] clockevents_notify() removal Ingo Molnar
2015-04-02 22:19   ` Rafael J. Wysocki
2015-04-02 23:45     ` [v2][PATCH 00/21] " Rafael J. Wysocki
2015-04-02 23:46       ` [v2][PATCH 01/21] ACPI / PAD: Remove the local APIC nonsense Rafael J. Wysocki
2015-04-03  8:21         ` tip-bot for Thomas Gleixner [this message]
2015-04-03  0:01       ` [v2][PATCH 02/21] clockevents: Provide explicit broadcast control functions Rafael J. Wysocki
2015-04-03  8:21         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:01       ` [v2][PATCH 03/21] x86, amd_idle: Use explicit broadcast control function Rafael J. Wysocki
2015-04-03  8:22         ` [tip:timers/core] x86/amd/idle, clockevents: " tip-bot for Thomas Gleixner
2015-04-03  0:01       ` [v2][PATCH 04/21] ACPI / PAD: " Rafael J. Wysocki
2015-04-03  8:22         ` [tip:timers/core] ACPI/PAD: " tip-bot for Thomas Gleixner
2015-04-03  0:02       ` [v2][PATCH 05/21] ACPI / processor: " Rafael J. Wysocki
2015-04-03  8:22         ` [tip:timers/core] ACPI/processor: " tip-bot for Thomas Gleixner
2015-04-03  0:02       ` [v2][PATCH 06/21] cpuidle: " Rafael J. Wysocki
2015-04-03  8:23         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:02       ` [v2][PATCH 07/21] intel_idle: " Rafael J. Wysocki
2015-04-03  8:23         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:02       ` [v2][PATCH 08/21] ARM: OMAP: " Rafael J. Wysocki
2015-04-03  8:23         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:03       ` [v2][PATCH 09/21] clockevents: Remove the broadcast control leftovers Rafael J. Wysocki
2015-04-03  8:23         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:05       ` [v2][PATCH 10/21] clockevents: Provide explicit broadcast oneshot control functions Rafael J. Wysocki
2015-04-03  8:24         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:05       ` [v2][PATCH 11/21] x86, amd_idle: Use " Rafael J. Wysocki
2015-04-03  8:24         ` [tip:timers/core] x86/amd/idle, clockevents: " tip-bot for Thomas Gleixner
2015-04-03  0:06       ` [v2][PATCH 12/21] ACPI / PAD: Use explicit broadcast oneshot control function Rafael J. Wysocki
2015-04-03  8:24         ` [tip:timers/core] ACPI/PAD: " tip-bot for Thomas Gleixner
2015-04-03  0:12       ` [v2][PATCH 13/21] ACPI / processor: Use explicit broadcast controll function Rafael J. Wysocki
2015-04-03  8:25         ` [tip:timers/core] ACPI/idle: Use explicit broadcast control function tip-bot for Thomas Gleixner
2015-04-03  0:14       ` [v2][PATCH 14/21] intel_idle: Use explicit broadcast oneshot " Rafael J. Wysocki
2015-04-03  8:25         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:31       ` [v2][PATCH 15/21] ARM: OMAP: " Rafael J. Wysocki
2015-04-03  8:25         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:32       ` [v2][PATCH 16/21] ARM: tegra: " Rafael J. Wysocki
2015-04-03  8:25         ` [tip:timers/core] ARM: Tegra: " tip-bot for Thomas Gleixner
2015-04-03  0:34       ` [v2][PATCH 17/21] sched/idle: " Rafael J. Wysocki
2015-04-03  8:26         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:36       ` [v2][PATCH 18/21] clockevents: Remove broadcast oneshot control leftovers Rafael J. Wysocki
2015-04-03  8:26         ` [tip:timers/core] " tip-bot for Rafael J. Wysocki
2015-04-03  0:37       ` [v2][PATCH 19/21] clockevents: Make tick handover explicit Rafael J. Wysocki
2015-04-03  8:26         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:38       ` [v2][PATCH 20/21] clockevents: Cleanup dead cpu explicitely Rafael J. Wysocki
2015-04-03  8:26         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:39       ` [v2][PATCH 21/21] timekeeping: Get rid of stale comment Rafael J. Wysocki
2015-04-03  8:27         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  6:45       ` [v2][PATCH 00/21] clockevents_notify() removal Ingo Molnar

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