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/*
 * Copyright (C) 2009 Bahadir Balban
 */

#include <l4lib/arch/arm/asm.h>
#include <l4lib/mutex.h>

/*
 * @r0 = address of mutex word
 */
BEGIN_PROC(__l4_mutex_lock)
1:
        ldrex   r1, [r0]                        @ Load value
        add     r1, r1, #1                      @ Add 1
        strex   r3, r1, [r0]                    @ Store prospective lock state
        cmp     r3, #0                          @ If not successful
        bne     1b                              @ Retry and decide again on the prospective lock state. No WFE as this would be a problem on single cpu
        dsb

        cmp     r1, #L4_MUTEX_LOCKED            @ We succeeded in store, but are we a locker or a contender?
        movne   r2, #L4_MUTEX_CONTENDED
        moveq   r2, #L4_MUTEX_SUCCESS
        mov     r0, r2
        mov     pc, lr
END_PROC(__l4_mutex_lock)

/*
 * @r0 = address of mutex word
 */
BEGIN_PROC(__l4_mutex_unlock)
        dsb
        mov     r3, #L4_MUTEX_UNLOCKED
1:
        ldrex   r1, [r0]
        strex   r2, r3, [r0]
        cmp     r2, #0
        bne     1b
        mov     r0, r1
        mov     pc, lr
END_PROC(__l4_mutex_unlock)