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/* $OpenBSD: mutex.S,v 1.4 2005/07/26 08:11:11 art Exp $ */
/*
* Copyright (c) 2004 Artur Grabowski <art@openbsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "assym.h"
#include <machine/param.h>
#include <machine/asm.h>
#include <machine/segments.h>
#include <machine/specialreg.h>
#include <machine/trap.h>
#include <machine/frameasm.h>
/*
* Yeah, we don't really need to implement mtx_init here, but let's keep
* all the functions in the same place.
*/
ENTRY(mtx_init)
movl %esi, MTX_WANTIPL(%rdi)
movl $0, MTX_OLDIPL(%rdi)
movq $0, MTX_OWNER(%rdi)
ret
ENTRY(mtx_enter)
1: movl MTX_WANTIPL(%rdi), %eax
movq CPUVAR(SELF), %rcx
movl CPU_INFO_ILEVEL(%rcx), %edx # oipl = cpl;
cmpl %eax, %edx # if (cpl < mtx->mtx_wantipl)
cmovge %edx, %eax
movl %eax, CPU_INFO_ILEVEL(%rcx) # cpl = mtx->mtx_wantipl;
/*
* %edx - the old ipl
* %rcx - curcpu()
*/
xorq %rax, %rax
#ifdef MULTIPROCESSOR
lock
#endif
cmpxchgq %rcx, MTX_OWNER(%rdi) # test_and_set(mtx->mtx_owner)
jne 2f
movl %edx, MTX_OLDIPL(%rdi)
ret
/* We failed to obtain the lock. splx, spin and retry. */
2: pushq %rdi
movl %edx, %edi
call _C_LABEL(spllower)
popq %rdi
#ifdef DIAGNOSTIC
movq CPUVAR(SELF), %rcx
cmpq MTX_OWNER(%rdi), %rcx
je 4f
#endif
3:
movq MTX_OWNER(%rdi), %rax
testq %rax, %rax
jz 1b
jmp 3b
#ifdef DIAGNOSTIC
4: movq $5f, %rdi
call _C_LABEL(panic)
5: .asciz "mtx_enter: locking against myself"
#endif
ENTRY(mtx_leave)
movq %rdi, %rax
xorq %rcx, %rcx
movl MTX_OLDIPL(%rax), %edi
movl %ecx, MTX_OLDIPL(%rax)
movq %rcx, MTX_OWNER(%rax)
cmpl %edi, CPUVAR(ILEVEL)
je 1f
call _C_LABEL(spllower)
1:
ret
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