linux-kernel - [PATCH 06/18] x86 idle: deprecate mwait_idle() and "idle=mwait" cmdline param

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Date:	Sat, 02 Apr 2011 02:22:48 -0400
From:	Len Brown <lenb@...nel.org>
To:	linux-pm@...ts.linux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	x86@...nel.org, stable@...nel.org
Subject: [PATCH 06/18] x86 idle: deprecate mwait_idle() and "idle=mwait"
 cmdline param

From: Len Brown <len.brown@...el.com>

mwait_idle() is a C1-only idle loop intended to be more efficient
than HLT on SMP hardware that supports it.

But mwait_idle() has been replaced by the more general
mwait_idle_with_hints(), which handles both C1 and deeper C-states.
ACPI uses only mwait_idle_with_hints(), and never uses mwait_idle().

Deprecate mwait_idle() and the "idle=mwait" cmdline param
to simplify the x86 idle code.

After this change, kernels configured with
(!CONFIG_ACPI=n && !CONFIG_INTEL_IDLE=n) when run on hardware
that support MWAIT will simply use HLT.  If MWAIT is desired
on those systems, cpuidle and the cpuidle drivers above
will support it.

cc: x86@...nel.org
cc: stable@...nel.org
Signed-off-by: Len Brown <len.brown@...el.com>
---
 Documentation/feature-removal-schedule.txt |    7 +++++++
 arch/x86/kernel/process.c                  |    1 +
 2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index f587159..9ee4a2c 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -35,6 +35,13 @@ Who:	Len Brown <len.brown@...el.com>
 
 ----------------------------
 
+What:	x86 "idle=mwait" cmdline param
+When:	2.6.40
+Why:	simplify x86 idle code
+Who:	Len Brown <len.brown@...el.com>
+
+----------------------------
+
 What:	PRISM54
 When:	2.6.34
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 17b8771..1f64501 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -645,6 +645,7 @@ static int __init idle_setup(char *str)
 		boot_option_idle_override = IDLE_POLL;
 	} else if (!strcmp(str, "mwait")) {
 		boot_option_idle_override = IDLE_FORCE_MWAIT;
+		WARN_ONCE(1, "\idle=mwait\" will be removed in 2.6.40\"\n");
 	} else if (!strcmp(str, "halt")) {
 		/*
 		 * When the boot option of idle=halt is added, halt is
-- 
1.7.5.rc0

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