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On second thought, implement x86_pause() as a regular function. The small

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delay from the call is useful for spinlock backoff.
This commit is contained in:
ad 2007-01-14 14:03:00 +00:00
parent ad9091c30f
commit d0a255a895
3 changed files with 20 additions and 14 deletions
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8
sys/arch/amd64/include/cpufunc.h
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@ -1,4 +1,4 @@
/* $NetBSD: cpufunc.h,v 1.11 2007/01/12 20:22:04 ad Exp $ */
/* $NetBSD: cpufunc.h,v 1.12 2007/01/14 14:03:00 ad Exp $ */
/*-
* Copyright (c) 1998 The NetBSD Foundation, Inc.
@ -49,11 +49,7 @@
#include <machine/segments.h>
#include <machine/specialreg.h>
static __inline void
x86_pause(void)
{
__asm volatile("pause");
}
void x86_pause(void);
/*
* XXX if lfence isn't available...

8
sys/arch/i386/include/cpufunc.h
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@ -1,4 +1,4 @@
/* $NetBSD: cpufunc.h,v 1.34 2007/01/01 20:56:59 ad Exp $ */
/* $NetBSD: cpufunc.h,v 1.35 2007/01/14 14:03:00 ad Exp $ */
/*-
* Copyright (c) 1998 The NetBSD Foundation, Inc.
@ -49,11 +49,7 @@
#include <machine/segments.h>
#include <machine/specialreg.h>
static __inline void
x86_pause(void)
{
__asm volatile("pause");
}
void x86_pause(void);
/*
* XXX it's better to use real lfence insn if available.

18
sys/arch/x86/x86/x86_machdep.c
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@ -1,4 +1,4 @@
/* $NetBSD: x86_machdep.c,v 1.5 2006/12/26 10:43:44 elad Exp $ */
/* $NetBSD: x86_machdep.c,v 1.6 2007/01/14 14:03:00 ad Exp $ */
/*-
* Copyright (c) 2005 The NetBSD Foundation, Inc.
@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: x86_machdep.c,v 1.5 2006/12/26 10:43:44 elad Exp $");
__KERNEL_RCSID(0, "$NetBSD: x86_machdep.c,v 1.6 2007/01/14 14:03:00 ad Exp $");
#include <sys/types.h>
#include <sys/param.h>
@ -115,3 +115,17 @@ check_pa_acc(paddr_t pa, vm_prot_t prot)
return EPERM;
}
/*
* Issue the pause instruction (rep; nop) which acts as a hint to
* HyperThreading processors that we are spinning on a lock.
*
* Not defined as an inline, because even if the CPU does not support
* HT the delay resulting from a function call is useful for spin lock
* back off.
*/
void
x86_pause(void)
{
__asm volatile("pause");
}