linux-kernel - [PATCH] v2: x86,APIC: Detect lapic_is_integrated() once

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Date:	Tue, 26 May 2009 07:20:31 +0600
From:	Rakib Mullick <rakib.mullick@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, macro@...ux-mips.org,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] v2: x86,APIC: Detect lapic_is_integrated() once - use on and 
	on

 This patch was sent previously (http://lkml.org/lkml/2009/5/22/240) -
but that one contains flaw as that one prevents compiler to optimize
the X86_64 case out. Thomas Gleixner (so thanks Thomas) shows how to
prevent that flaw. Also it helps to avoid cache line pollution. So, I
think with this patch everyone would be happy.
		
Thanks,
--
Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>

--- linus/arch/x86/kernel/apic/apic.c	2009-05-25 00:20:25.000000000 +0600
+++ rakib/arch/x86/kernel/apic/apic.c	2009-05-25 00:50:08.333910872 +0600
@@ -127,6 +127,13 @@ early_param("nox2apic", setup_nox2apic);

 unsigned long mp_lapic_addr;
 int disable_apic;
+
+#ifdef	CONFIG_X86_64
+# define integrated_lapic (1)
+#else
+static int integrated_lapic __read_mostly;
+#endif
+
 /* Disable local APIC timer from the kernel commandline or via dmi quirk */
 static int disable_apic_timer __cpuinitdata;
 /* Local APIC timer works in C2 */
@@ -188,12 +195,10 @@ static inline int lapic_get_version(void
 /*
  * Check, if the APIC is integrated or a separate chip
  */
-static inline int lapic_is_integrated(void)
+static inline void lapic_is_integrated(void)
 {
-#ifdef CONFIG_X86_64
-	return 1;
-#else
-	return APIC_INTEGRATED(lapic_get_version());
+#ifdef CONFIG_X86_32
+	integrated_lapic = APIC_INTEGRATED(lapic_get_version());
 #endif
 }

@@ -258,7 +263,7 @@ void __cpuinit enable_NMI_through_LVT0(v
 	v = APIC_DM_NMI;

 	/* Level triggered for 82489DX (32bit mode) */
-	if (!lapic_is_integrated())
+	if (!integrated_lapic)
 		v |= APIC_LVT_LEVEL_TRIGGER;

 	apic_write(APIC_LVT0, v);
@@ -313,7 +318,7 @@ static void __setup_APIC_LVTT(unsigned i
 	lvtt_value = LOCAL_TIMER_VECTOR;
 	if (!oneshot)
 		lvtt_value |= APIC_LVT_TIMER_PERIODIC;
-	if (!lapic_is_integrated())
+	if (!integrated_lapic)
 		lvtt_value |= SET_APIC_TIMER_BASE(APIC_TIMER_BASE_DIV);

 	if (!irqen)
@@ -869,7 +874,7 @@ void clear_local_APIC(void)
 		apic_write(APIC_LVTPC, APIC_LVT_MASKED);

 	/* Integrated APIC (!82489DX) ? */
-	if (lapic_is_integrated()) {
+	if (integrated_lapic) {
 		if (maxlvt > 3)
 			/* Clear ESR due to Pentium errata 3AP and 11AP */
 			apic_write(APIC_ESR, 0);
@@ -1064,7 +1069,7 @@ void __init init_bsp_APIC(void)
 	 */
 	apic_write(APIC_LVT0, APIC_DM_EXTINT);
 	value = APIC_DM_NMI;
-	if (!lapic_is_integrated())		/* 82489DX */
+	if (!integrated_lapic)		/* 82489DX */
 		value |= APIC_LVT_LEVEL_TRIGGER;
 	apic_write(APIC_LVT1, value);
 }
@@ -1073,7 +1078,7 @@ static void __cpuinit lapic_setup_esr(vo
 {
 	unsigned int oldvalue, value, maxlvt;

-	if (!lapic_is_integrated()) {
+	if (!integrated_lapic) {
 		pr_info("No ESR for 82489DX.\n");
 		return;
 	}
@@ -1126,7 +1131,7 @@ void __cpuinit setup_local_APIC(void)

 #ifdef CONFIG_X86_32
 	/* Pound the ESR really hard over the head with a big hammer - mbligh */
-	if (lapic_is_integrated() && apic->disable_esr) {
+	if (integrated_lapic && apic->disable_esr) {
 		apic_write(APIC_ESR, 0);
 		apic_write(APIC_ESR, 0);
 		apic_write(APIC_ESR, 0);
@@ -1251,7 +1256,7 @@ void __cpuinit setup_local_APIC(void)
 		value = APIC_DM_NMI;
 	else
 		value = APIC_DM_NMI | APIC_LVT_MASKED;
-	if (!lapic_is_integrated())		/* 82489DX */
+	if (!integrated_lapic)		/* 82489DX */
 		value |= APIC_LVT_LEVEL_TRIGGER;
 	apic_write(APIC_LVT1, value);

@@ -1599,6 +1604,8 @@ int __init APIC_init_uniprocessor(void)
 		clear_cpu_cap(&boot_cpu_data, X86_FEATURE_APIC);
 		return -1;
 	}
+	/* Determine APIC is integrated or not.	*/
+	lapic_is_integrated();
 #endif

 	enable_IR_x2apic();
--
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