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Message-Id: <4B62A40B020000780002CA99@vpn.id2.novell.com>
Date: Fri, 29 Jan 2010 08:02:03 +0000
From: "Jan Beulich" <JBeulich@...ell.com>
To: <mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc: "Jeremy Fitzhardinge" <jeremy@...p.org>,
<linux-kernel@...r.kernel.org>
Subject: [PATCH 3/3] x86: enlightenment for ticket spinlocks - remove
NOPs from unlock path
Under the assumption that the nop-s added by the base ticket spinlock
enlightenment patch might be considered undesirable (or worse), here
is an optional patch to eliminate these nop-s again. This is done
through extending the memory operands of the inc instructions used for
unlocking ticket locks to the necessary size, using assembler and
linker features.
Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
arch/x86/Makefile | 3 +
arch/x86/include/asm/alternative-asm.h | 59 +++++++++++++++++++++++++++++++++
arch/x86/include/asm/alternative.h | 5 ++
arch/x86/include/asm/spinlock.h | 27 ++++-----------
arch/x86/kernel/symdefs.lds | 1
arch/x86/kernel/vmlinux.lds.S | 2 +
6 files changed, 78 insertions(+), 19 deletions(-)
--- 2.6.33-rc5-virt-spinlocks.orig/arch/x86/Makefile
+++ 2.6.33-rc5-virt-spinlocks/arch/x86/Makefile
@@ -87,6 +87,9 @@ ifeq ($(CONFIG_KMEMCHECK),y)
KBUILD_CFLAGS += $(call cc-option,-fno-builtin-memcpy)
endif
+KBUILD_CFLAGS += -Wa,-I$(srctree)/arch/x86/include
+LDFLAGS_MODULE += -T $(srctree)/arch/x86/kernel/symdefs.lds
+
# Stackpointer is addressed different for 32 bit and 64 bit x86
sp-$(CONFIG_X86_32) := esp
sp-$(CONFIG_X86_64) := rsp
--- 2.6.33-rc5-virt-spinlocks.orig/arch/x86/include/asm/alternative.h
+++ 2.6.33-rc5-virt-spinlocks/arch/x86/include/asm/alternative.h
@@ -6,6 +6,11 @@
#include <linux/stringify.h>
#include <asm/asm.h>
+#if !defined(__ASSEMBLY__) && !defined(__PIC__)
+#include <asm/alternative-asm.h> /* just for tracking the build dependency */
+__asm__(".include \"asm/alternative-asm.h\"");
+#endif
+
/*
* Alternative inline assembly for SMP.
*
--- 2.6.33-rc5-virt-spinlocks.orig/arch/x86/include/asm/alternative-asm.h
+++ 2.6.33-rc5-virt-spinlocks/arch/x86/include/asm/alternative-asm.h
@@ -1,3 +1,7 @@
+#if 0 /* Hide this from compiler. */
+ .if 0 # Hide assembly source stuff when assembling compiler output.
+#endif
+
#ifdef __ASSEMBLY__
#include <asm/asm.h>
@@ -16,3 +20,58 @@
#endif
#endif /* __ASSEMBLY__ */
+
+#if 0 /* Hide this from compiler. */
+ .else # Code to be used in compiler output:
+
+ .weak _$.zero
+
+ .macro unary opc arg1 arg2 arg3
+ .Lempty=2
+ .irpc c,"\arg2"
+ .Lempty=3
+ .endr
+ .irpc c,"\arg3"
+ .Lempty=0
+ .endr
+ .Lsym=1
+ .Lnum=0
+ .irpc c,"\arg1"
+ .irpc m,"(123456789-0"
+ .ifeqs "\c","\m"
+ .Lsym=0
+ .exitm
+ .endif
+ .Lnum=1
+ .endr
+ .exitm
+ .endr
+ .if .Lempty == 2
+ .if .Lsym
+ \opc \arg1
+ .elseif .Lnum
+ \opc _$.zero+\arg1
+ .else
+ \opc _$.zero\arg1
+ .endif
+ .elseif .Lempty == 3
+ .if .Lsym
+ \opc \arg1,\arg2
+ .elseif .Lnum
+ \opc _$.zero+\arg1,\arg2
+ .else
+ \opc _$.zero\arg1,\arg2
+ .endif
+ .else
+ .if .Lsym
+ \opc \arg1,\arg2,\arg3
+ .elseif .Lnum
+ \opc _$.zero+\arg1,\arg2,\arg3
+ .else
+ \opc _$.zero\arg1,\arg2,\arg3
+ .endif
+ .endif
+ .endm
+
+ .endif
+#endif
--- 2.6.33-rc5-virt-spinlocks.orig/arch/x86/include/asm/spinlock.h
+++ 2.6.33-rc5-virt-spinlocks/arch/x86/include/asm/spinlock.h
@@ -10,7 +10,6 @@
#ifdef CONFIG_ENLIGHTEN_SPINLOCKS
#include <asm/alternative.h>
-#include <asm/nops.h>
/* Including asm/smp.h here causes a cyclic include dependency. */
#include <asm/percpu.h>
DECLARE_PER_CPU(int, cpu_number);
@@ -155,20 +154,15 @@ static __always_inline int __ticket_spin
static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
{
#ifndef CONFIG_ENLIGHTEN_SPINLOCKS
- asm volatile(
+ asm volatile(UNLOCK_LOCK_PREFIX "incb %0"
+ : "+m" (lock->slock)
+ :
#else
unsigned int token;
alternative_io(
".L%=orig:\n\t"
-#endif
- UNLOCK_LOCK_PREFIX "incb %0"
-#ifndef CONFIG_ENLIGHTEN_SPINLOCKS
- : "+m" (lock->slock)
- :
-#else
- "\n\t"
- ASM_NOP3
+ UNLOCK_LOCK_PREFIX "unary incb %0\n\t"
".L%=done:",
".L%=alt:\n\t"
/* jmp .L%=callout */
@@ -286,20 +280,15 @@ static __always_inline int __ticket_spin
static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
{
#ifndef CONFIG_ENLIGHTEN_SPINLOCKS
- asm volatile(
+ asm volatile(UNLOCK_LOCK_PREFIX "incw %0"
+ : "+m" (lock->slock)
+ :
#else
unsigned int token, tmp;
alternative_io(
".L%=orig:\n\t"
-#endif
- UNLOCK_LOCK_PREFIX "incw %0"
-#ifndef CONFIG_ENLIGHTEN_SPINLOCKS
- : "+m" (lock->slock)
- :
-#else
- "\n\t"
- ASM_NOP2
+ UNLOCK_LOCK_PREFIX "unary incw %0\n\t"
".L%=done:",
".L%=alt:\n\t"
/* jmp .L%=callout */
--- /dev/null
+++ 2.6.33-rc5-virt-spinlocks/arch/x86/kernel/symdefs.lds
@@ -0,0 +1 @@
+_$.zero = 0;
--- 2.6.33-rc5-virt-spinlocks.orig/arch/x86/kernel/vmlinux.lds.S
+++ 2.6.33-rc5-virt-spinlocks/arch/x86/kernel/vmlinux.lds.S
@@ -27,6 +27,8 @@
#include <asm/cache.h>
#include <asm/boot.h>
+#include "symdefs.lds"
+
#undef i386 /* in case the preprocessor is a 32bit one */
OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT)
--
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