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Implement __cpu_simple_lock*() primitives using the SWP insn. Note 

this insn is available only on ARM arch v3 and later (and 2a).  We
don't expect to be using these ops in the kernel on processors too
old to have SWP, and for userland uses (in e.g. a pthread library),
the kernel will simply have to trap and emulate the insn (it needs
to be "atomic", so a kernel trap of some sort will be necessary on
such platforms anyway).
This commit is contained in:
thorpej 2001-11-15 19:22:32 +00:00
parent d751d184e1
commit 0b6370bfee
1 changed files with 51 additions and 6 deletions
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57
sys/arch/arm/include/lock.h
View File

@ -1,7 +1,7 @@
/* $NetBSD: lock.h,v 1.1 2001/01/10 19:02:07 bjh21 Exp $ */
/* $NetBSD: lock.h,v 1.2 2001/11/15 19:22:32 thorpej Exp $ */
/*-
* Copyright (c) 2000 The NetBSD Foundation, Inc.
* Copyright (c) 2000, 2001 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
@ -38,14 +38,59 @@
/*
* Machine-dependent spin lock operations.
*
* NOTE: The SWP insn used here is available only on ARM architecture
* version 3 and later (as well as 2a). What we are going to do is
* expect that the kernel will trap and emulate the insn. That will
* be slow, but give us the atomicity that we need.
*/
#ifndef _ARM32_LOCK_H_
#define _ARM32_LOCK_H_
#ifndef _ARM_LOCK_H_
#define _ARM_LOCK_H_
typedef int __cpu_simple_lock_t;
typedef __volatile int __cpu_simple_lock_t;
#define __SIMPLELOCK_LOCKED 1
#define __SIMPLELOCK_UNLOCKED 0
#endif /* _ARM32_LOCK_H_ */
static __inline void __attribute__((__unused__))
__cpu_simple_lock_init(__cpu_simple_lock_t *alp)
{
*alp = __SIMPLELOCK_UNLOCKED;
}
static __inline void __attribute__((__unused__))
__cpu_simple_lock(__cpu_simple_lock_t *alp)
{
int __val = __SIMPLELOCK_LOCKED;
do {
__asm __volatile("swp %0, %1, [%2]"
: "=r" (__val)
: "0" (__val), "r" (alp)
: "memory");
} while (__val != __SIMPLELOCK_UNLOCKED);
}
static __inline int __attribute__((__unused__))
__cpu_simple_lock_try(__cpu_simple_lock_t *alp)
{
int __val = __SIMPLELOCK_LOCKED;
__asm __volatile("swp %0, %1, [%2]"
: "=r" (__val)
: "0" (__val), "r" (alp)
: "memory");
return ((__val == __SIMPLELOCK_UNLOCKED) ? 1 : 0);
}
static __inline void __attribute__((__unused__))
__cpu_simple_unlock(__cpu_simple_lock_t *alp)
{
*alp = __SIMPLELOCK_UNLOCKED;
}
#endif /* _ARM_LOCK_H_ */