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This commit is contained in:
Bahadir Balban
2008-01-13 13:53:52 +00:00
commit e2b791a3d8
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90
src/arch/arm/v5/mutex.S Normal file
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/*
* ARM v5 Binary semaphore (mutex) implementation.
*
* Copyright (C) 2007 Bahadir Balban
*
*/
#include INC_ARCH(asm.h)
/* Recap on swp:
* swp rx, ry, [rz]
* In one instruction:
* 1) Stores the value in ry into location pointed by rz.
* 2) Loads the value in the location of rz into rx.
* By doing so, in one instruction one can attempt to lock
* a word, and discover whether it was already locked.
*/
#define MUTEX_UNLOCKED 0
#define MUTEX_LOCKED 1
BEGIN_PROC(__spin_lock)
mov r1, #1
__spin:
swp r2, r1, [r0]
cmp r2, #0
bne __spin
mov pc, lr
END_PROC(__spin_lock)
BEGIN_PROC(__spin_unlock)
mov r1, #0
swp r2, r1, [r0]
cmp r2, #1 @ Debug check.
1:
bne 1b
mov pc, lr
END_PROC(__spin_unlock)
/*
* @r0: Address of mutex location.
*/
BEGIN_PROC(__mutex_lock)
mov r1, #1
swp r2, r1, [r0]
cmp r2, #0
movne r0, #0
moveq r0, #1
mov pc, lr
END_PROC(__mutex_lock)
/*
* @r0: Address of mutex location.
*/
BEGIN_PROC(__mutex_unlock)
mov r1, #0
swp r2, r1, [r0]
cmp r2, #1
1: @ Debug check.
bne 1b
mov pc, lr
END_PROC(__mutex_unlock)
/*
* @r0: Address of mutex location.
*/
BEGIN_PROC(__mutex_inc)
swp r2, r1, [r0]
mov r1, #1
swp r2, r1, [r0]
cmp r2, #0
movne r0, #0
moveq r0, #1
mov pc, lr
END_PROC(__mutex_inc)
/*
* @r0: Address of mutex location.
*/
BEGIN_PROC(__mutex_dec)
mov r1, #0
swp r2, r1, [r0]
cmp r2, #1
1: @ Debug check.
bne 1b
mov pc, lr
END_PROC(__mutex_dec)