linux-kernel - Re: [PATCH] x86: Replace uses of current_cpu_data with this

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Date:	Wed, 8 Dec 2010 11:33:29 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Tejun Heo <tj@...nel.org>
cc:	Eric Dumazet <eric.dumazet@...il.com>, akpm@...ux-foundation.org,
	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH] x86: Replace uses of current_cpu_data with this_cpu
 ops

Beginnings of a patch to avoid bitops. If you think this is the right way
then I will complete it for all uses of cpu_has.


---
 arch/x86/include/asm/cpufeature.h |   15 +++++++++++++++
 arch/x86/kernel/apic/apic.c       |    2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

Index: linux-2.6/arch/x86/include/asm/cpufeature.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/cpufeature.h	2010-12-08 09:39:31.000000000 -0600
+++ linux-2.6/arch/x86/include/asm/cpufeature.h	2010-12-08 09:40:02.000000000 -0600
@@ -221,6 +221,21 @@ extern const char * const x86_power_flag
 	  ? 1 :								\
 	 test_cpu_cap(c, bit))

+#define this_cpu_has(bit)							\
+	(__builtin_constant_p(bit) &&					\
+	 ( (((bit)>>5)==0 && (1UL<<((bit)&31) & REQUIRED_MASK0)) ||	\
+	   (((bit)>>5)==1 && (1UL<<((bit)&31) & REQUIRED_MASK1)) ||	\
+	   (((bit)>>5)==2 && (1UL<<((bit)&31) & REQUIRED_MASK2)) ||	\
+	   (((bit)>>5)==3 && (1UL<<((bit)&31) & REQUIRED_MASK3)) ||	\
+	   (((bit)>>5)==4 && (1UL<<((bit)&31) & REQUIRED_MASK4)) ||	\
+	   (((bit)>>5)==5 && (1UL<<((bit)&31) & REQUIRED_MASK5)) ||	\
+	   (((bit)>>5)==6 && (1UL<<((bit)&31) & REQUIRED_MASK6)) ||	\
+	   (((bit)>>5)==7 && (1UL<<((bit)&31) & REQUIRED_MASK7)) ||	\
+	   (((bit)>>5)==8 && (1UL<<((bit)&31) & REQUIRED_MASK8)) ||	\
+	   (((bit)>>5)==9 && (1UL<<((bit)&31) & REQUIRED_MASK9)) )	\
+	  ? 1 :								\
+	 (this_cpu_read(cpu_info.x86_capabilty) & (1 << bit)))
+
 #define boot_cpu_has(bit)	cpu_has(&boot_cpu_data, bit)

 #define set_cpu_cap(c, bit)	set_bit(bit, (unsigned long *)((c)->x86_capability))
Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/apic.c	2010-12-08 09:40:37.000000000 -0600
+++ linux-2.6/arch/x86/kernel/apic/apic.c	2010-12-08 09:40:49.000000000 -0600
@@ -516,7 +516,7 @@ static void __cpuinit setup_APIC_timer(v
 {
 	struct clock_event_device *levt = &__get_cpu_var(lapic_events);

-	if (cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_ARAT)) {
+	if (this_cpu_has(X86_FEATURE_ARAT)) {
 		lapic_clockevent.features &= ~CLOCK_EVT_FEAT_C3STOP;
 		/* Make LAPIC timer preferrable over percpu HPET */
 		lapic_clockevent.rating = 150;
--
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