linux-kernel - [PATCH 3/4] x86: Extend IPIless wake to C1_mwait and poll

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Date:	Fri, 24 Feb 2012 14:33:19 -0800
From:	Venkatesh Pallipadi <venki@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Aaron Durbin <adurbin@...gle.com>,
	Paul Turner <pjt@...gle.com>,
	Yong Zhang <yong.zhang0@...il.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Venkatesh Pallipadi <venki@...gle.com>
Subject: [PATCH 3/4] x86: Extend IPIless wake to C1_mwait and poll_idle

poll_idle(), mwait_idle() [which is used for C1 mwait] and any other
polling based idle loops can also use the IPIless wakeup logic added
with mwait_idle_with_hints() in the earlier patch.

Signed-off-by: Venkatesh Pallipadi <venki@...gle.com>
---
 arch/x86/kernel/process.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 99a8109..43bb0a5 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -22,6 +22,7 @@
 #include <asm/uaccess.h>
 #include <asm/i387.h>
 #include <asm/debugreg.h>
+#include <asm/ipiless_wake.h>
 
 struct kmem_cache *task_xstate_cachep;
 EXPORT_SYMBOL_GPL(task_xstate_cachep);
@@ -445,7 +446,8 @@ EXPORT_SYMBOL_GPL(cpu_idle_wait);
 /* Default MONITOR/MWAIT with no hints, used for default C1 state */
 static void mwait_idle(void)
 {
-	if (!need_resched()) {
+	enter_ipiless_idle();
+	if (!is_ipiless_wakeup_pending()) {
 		trace_power_start(POWER_CSTATE, 1, smp_processor_id());
 		trace_cpu_idle(1, smp_processor_id());
 		if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
@@ -453,7 +455,7 @@ static void mwait_idle(void)
 
 		__monitor((void *)&current_thread_info()->flags, 0, 0);
 		smp_mb();
-		if (!need_resched())
+		if (!is_ipiless_wakeup_pending())
 			__sti_mwait(0, 0);
 		else
 			local_irq_enable();
@@ -461,6 +463,7 @@ static void mwait_idle(void)
 		trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
 	} else
 		local_irq_enable();
+	exit_ipiless_idle();
 }
 
 /*
@@ -470,13 +473,15 @@ static void mwait_idle(void)
  */
 static void poll_idle(void)
 {
+	enter_ipiless_idle();
 	trace_power_start(POWER_CSTATE, 0, smp_processor_id());
 	trace_cpu_idle(0, smp_processor_id());
 	local_irq_enable();
-	while (!need_resched())
+	while (!is_ipiless_wakeup_pending())
 		cpu_relax();
 	trace_power_end(smp_processor_id());
 	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
+	exit_ipiless_idle();
 }
 
 /*
-- 
1.7.7.3

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