atomic_arm.h

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/* 
 * Copyright (C) 2006 iptelorg GmbH
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* 
 * History:
 * --------
 *  2006-03-31  created by andrei
 *  2007-05-10  added atomic_add and atomic_cmpxchg (andrei)
 *  2007-05-29  added membar_depends(), membar_*_atomic_op and
 *                membar_*_atomic_setget (andrei)
 */


#ifndef _atomic_arm_h
#define _atomic_arm_h




#ifdef NOSMP
#define HAVE_ASM_INLINE_MEMBAR
#define membar() asm volatile ("" : : : "memory") /* gcc do not cache barrier*/
#define membar_read()  membar()
#define membar_write() membar()
#define membar_depends()   do {} while(0) /* really empty, not even a cc bar.*/
/* lock barriers: empty, not needed for NOSMP; the lock/unlock should already
 * contain gcc barriers*/
#define membar_enter_lock() do {} while(0)
#define membar_leave_lock() do {} while(0)
/* membars after or before atomic_ops or atomic_setget -> use these or
 *  mb_<atomic_op_name>() if you need a memory barrier in one of these
 *  situations (on some archs where the atomic operations imply memory
 *   barriers is better to use atomic_op_x(); membar_atomic_op() then
 *    atomic_op_x(); membar()) */
#define membar_atomic_op()                              membar()
#define membar_atomic_setget()                  membar()
#define membar_write_atomic_op()                membar_write()
#define membar_write_atomic_setget()    membar_write()
#define membar_read_atomic_op()                 membar_read()
#define membar_read_atomic_setget()             membar_read()
#else /* SMP */
#warning SMP not supported for arm atomic ops, try compiling with -DNOSMP
/* fall back to default lock based barriers (don't define HAVE_ASM...) */
#endif /* NOSMP */


#ifdef __CPU_arm6


#define HAVE_ASM_INLINE_ATOMIC_OPS

/* hack to get some membars */
#ifndef NOSMP
#include "atomic_unknown.h"
#endif

/* main asm block 
 *  use %0 as input and write the output in %1*/
#define ATOMIC_ASM_OP(op) \
                        "1:   ldrex %0, [%3] \n\t" \
                        "     " op "\n\t" \
                        "     strex %0, %1, [%3] \n\t" \
                        "     cmp %0, #0 \n\t" \
                        "     bne 1b \n\t"

/* same as above but writes %4 instead of %1, and %0 will contain 
 * the prev. val*/
#define ATOMIC_ASM_OP2(op) \
                        "1:   ldrex %0, [%3] \n\t" \
                        "     " op "\n\t" \
                        "     strex %1, %4, [%3] \n\t" \
                        "     cmp %1, #0 \n\t" \
                        "     bne 1b \n\t"

/* no extra param, %0 contains *var, %1 should contain the result */
#define ATOMIC_FUNC_DECL(NAME, OP, P_TYPE, RET_TYPE, RET_EXPR) \
        inline static RET_TYPE atomic_##NAME##_##P_TYPE (volatile P_TYPE *var) \
        { \
                P_TYPE ret, tmp; \
                asm volatile( \
                        ATOMIC_ASM_OP(OP) \
                        : "=&r"(tmp), "=&r"(ret), "=m"(*var) : "r"(var)  : "cc" \
                        ); \
                return RET_EXPR; \
        }

/* one extra param in %4 */
#define ATOMIC_FUNC_DECL1(NAME, OP, P_TYPE, RET_TYPE, RET_EXPR) \
        inline static RET_TYPE atomic_##NAME##_##P_TYPE (volatile P_TYPE *var, \
                                                                                                                P_TYPE v) \
        { \
                P_TYPE ret, tmp; \
                asm volatile( \
                        ATOMIC_ASM_OP(OP) \
                        : "=&r"(tmp), "=&r"(ret), "=m"(*var) : "r"(var), "r"(v) : "cc" \
                        ); \
                return RET_EXPR; \
        }


/* as above, but %4 should contain the result, and %0 is returned*/
#define ATOMIC_FUNC_DECL2(NAME, OP, P_TYPE, RET_TYPE, RET_EXPR) \
        inline static RET_TYPE atomic_##NAME##_##P_TYPE (volatile P_TYPE *var, \
                                                                                                                P_TYPE v) \
        { \
                P_TYPE ret, tmp; \
                asm volatile( \
                        ATOMIC_ASM_OP2(OP) \
                        : "=&r"(ret), "=&r"(tmp), "=m"(*var) : "r"(var), "r"(v) : "cc" \
                        ); \
                return RET_EXPR; \
        }


#define ATOMIC_XCHG_DECL(NAME, P_TYPE) \
        inline static P_TYPE atomic_##NAME##_##P_TYPE (volatile P_TYPE *var, \
                                                                                                                P_TYPE v ) \
        { \
                P_TYPE ret; \
                asm volatile( \
                        "     swp %0, %2, [%3] \n\t" \
                        : "=&r"(ret),  "=m"(*var) :\
                                "r"(v), "r"(var) \
                        ); \
                return ret; \
        }


/* cmpxchg: %5=old, %4=new_v, %3=var
 * if (*var==old) *var=new_v
 * returns the original *var (can be used to check if it succeeded: 
 *  if old==cmpxchg(var, old, new_v) -> success
 */
#define ATOMIC_CMPXCHG_DECL(NAME, P_TYPE) \
        inline static P_TYPE atomic_##NAME##_##P_TYPE (volatile P_TYPE *var, \
                                                                                                                P_TYPE old, \
                                                                                                                P_TYPE new_v) \
        { \
                P_TYPE ret, tmp; \
                asm volatile( \
                        "1:   ldrex %0, [%3] \n\t" \
                        "     cmp %0, %5 \n\t" \
                        "     strexeq %1, %4, [%3] \n\t" \
                        "     cmp %1, #0 \n\t" \
                        "     bne 1b \n\t" \
                        /* strexeq is exec. only if cmp was successful \
                         * => if not successful %1 is not changed and remains 0 */ \
                        : "=&r"(ret), "=&r"(tmp), "=m"(*var) :\
                                "r"(var), "r"(new_v), "r"(old), "1"(0) : "cc" \
                        ); \
                return ret; \
        }



ATOMIC_FUNC_DECL(inc,      "add  %1, %0, #1", int, void, /* no return */ )
ATOMIC_FUNC_DECL(dec,      "sub  %1, %0, #1", int, void, /* no return */ )
ATOMIC_FUNC_DECL1(and,     "and  %1, %0, %4", int, void, /* no return */ )
ATOMIC_FUNC_DECL1(or,      "orr  %1, %0, %4", int, void, /* no return */ )
ATOMIC_FUNC_DECL(inc_and_test, "add  %1, %0, #1", int, int, ret==0 )
ATOMIC_FUNC_DECL(dec_and_test, "sub  %1, %0, #1", int, int, ret==0 )
//ATOMIC_FUNC_DECL2(get_and_set, /* no extra op needed */ , int, int,  ret)
ATOMIC_XCHG_DECL(get_and_set, int)
ATOMIC_CMPXCHG_DECL(cmpxchg, int)
ATOMIC_FUNC_DECL1(add,     "add  %1, %0, %4", int, int, ret )

ATOMIC_FUNC_DECL(inc,      "add  %1, %0, #1", long, void, /* no return */ )
ATOMIC_FUNC_DECL(dec,      "sub  %1, %0, #1", long, void, /* no return */ )
ATOMIC_FUNC_DECL1(and,     "and  %1, %0, %4", long, void, /* no return */ )
ATOMIC_FUNC_DECL1(or,      "orr  %1, %0, %4", long, void, /* no return */ )
ATOMIC_FUNC_DECL(inc_and_test, "add  %1, %0, #1", long, long, ret==0 )
ATOMIC_FUNC_DECL(dec_and_test, "sub  %1, %0, #1", long, long, ret==0 )
//ATOMIC_FUNC_DECL2(get_and_set, /* no extra op needed */ , long, long,  ret)
ATOMIC_XCHG_DECL(get_and_set, long)
ATOMIC_CMPXCHG_DECL(cmpxchg, long)
ATOMIC_FUNC_DECL1(add,     "add  %1, %0, %4", long, long, ret )

#define atomic_inc(var) atomic_inc_int(&(var)->val)
#define atomic_dec(var) atomic_dec_int(&(var)->val)
#define atomic_and(var, mask) atomic_and_int(&(var)->val, (mask))
#define atomic_or(var, mask)  atomic_or_int(&(var)->val, (mask))
#define atomic_dec_and_test(var) atomic_dec_and_test_int(&(var)->val)
#define atomic_inc_and_test(var) atomic_inc_and_test_int(&(var)->val)
#define atomic_get_and_set(var, i) atomic_get_and_set_int(&(var)->val, i)
#define atomic_cmpxchg(var, old, new_v) \
        atomic_cmpxchg_int(&(var)->val, old, new_v)
#define atomic_add(var, v) atomic_add_int(&(var)->val, (v))


/* with integrated membar */

#define mb_atomic_set_int(v, i) \
        do{ \
                membar(); \
                atomic_set_int(v, i); \
        }while(0)



inline static int mb_atomic_get_int(volatile int* v)
{
        membar();
        return atomic_get_int(v);
}


#define mb_atomic_inc_int(v) \
        do{ \
                membar(); \
                atomic_inc_int(v); \
        }while(0)

#define mb_atomic_dec_int(v) \
        do{ \
                membar(); \
                atomic_dec_int(v); \
        }while(0)

#define mb_atomic_or_int(v, m) \
        do{ \
                membar(); \
                atomic_or_int(v, m); \
        }while(0)

#define mb_atomic_and_int(v, m) \
        do{ \
                membar(); \
                atomic_and_int(v, m); \
        }while(0)

inline static int mb_atomic_inc_and_test_int(volatile int* v)
{
        membar();
        return atomic_inc_and_test_int(v);
}

inline static int mb_atomic_dec_and_test_int(volatile int* v)
{
        membar();
        return atomic_dec_and_test_int(v);
}


inline static int mb_atomic_get_and_set_int(volatile int* v, int i)
{
        membar();
        return atomic_get_and_set_int(v, i);
}

inline static int mb_atomic_cmpxchg_int(volatile int* v, int o, int n)
{
        membar();
        return atomic_cmpxchg_int(v, o, n);
}

inline static int mb_atomic_add_int(volatile int* v, int i)
{
        membar();
        return atomic_add_int(v, i);
}



#define mb_atomic_set_long(v, i) \
        do{ \
                membar(); \
                atomic_set_long(v, i); \
        }while(0)



inline static long mb_atomic_get_long(volatile long* v)
{
        membar();
        return atomic_get_long(v);
}


#define mb_atomic_inc_long(v) \
        do{ \
                membar(); \
                atomic_inc_long(v); \
        }while(0)


#define mb_atomic_dec_long(v) \
        do{ \
                membar(); \
                atomic_dec_long(v); \
        }while(0)

#define mb_atomic_or_long(v, m) \
        do{ \
                membar(); \
                atomic_or_long(v, m); \
        }while(0)

#define mb_atomic_and_long(v, m) \
        do{ \
                membar(); \
                atomic_and_long(v, m); \
        }while(0)

inline static long mb_atomic_inc_and_test_long(volatile long* v)
{
        membar();
        return atomic_inc_and_test_long(v);
}

inline static long mb_atomic_dec_and_test_long(volatile long* v)
{
        membar();
        return atomic_dec_and_test_long(v);
}


inline static long mb_atomic_get_and_set_long(volatile long* v, long l)
{
        membar();
        return atomic_get_and_set_long(v, l);
}

inline static long mb_atomic_cmpxchg_long(volatile long* v, long o, long n)
{
        membar();
        return atomic_cmpxchg_long(v, o, n);
}

inline static long mb_atomic_add_long(volatile long* v, long i)
{
        membar();
        return atomic_add_long(v, i);
}

#define mb_atomic_inc(var) mb_atomic_inc_int(&(var)->val)
#define mb_atomic_dec(var) mb_atomic_dec_int(&(var)->val)
#define mb_atomic_and(var, mask) mb_atomic_and_int(&(var)->val, (mask))
#define mb_atomic_or(var, mask)  mb_atomic_or_int(&(var)->val, (mask))
#define mb_atomic_dec_and_test(var) mb_atomic_dec_and_test_int(&(var)->val)
#define mb_atomic_inc_and_test(var) mb_atomic_inc_and_test_int(&(var)->val)
#define mb_atomic_get(var)      mb_atomic_get_int(&(var)->val)
#define mb_atomic_set(var, i)   mb_atomic_set_int(&(var)->val, i)
#define mb_atomic_get_and_set(var, i) mb_atomic_get_and_set_int(&(var)->val, i)
#define mb_atomic_cmpxchg(var, o, n) mb_atomic_cmpxchg_int(&(var)->val, o, n)
#define mb_atomic_add(var, i) mb_atomic_add_int(&(var)->val, i)



#else /* ! __CPU_arm6 => __CPU_arm */

/* no atomic ops for v <6 , only SWP supported
 * Atomic ops could be implemented if one bit is sacrificed and used like
 *  a spinlock, e.g:
 *          mov %r0, #0x1
 *       1: swp %r1, %r0, [&atomic_val]
 *          if (%r1 & 0x1) goto 1 # wait if first bit is 1 
 *          %r1>>=1  # restore the value (only 31 bits can be used )
 *          %r1=op (%r1, ...) 
 *          %r1<<=1   # shift back the value, such that the first bit is 0
 *          str %r1, [&atomic_val]  # write the value
 *
 * However only 31 bits could be used (=> atomic_*_int and atomic_*_long
 *  would still have to be lock based, since in these cases we guarantee all 
 *  the bits)  and I'm not sure there would be a significant performance
 *  benefit when compared with the fallback lock based version:
 *    lock(atomic_lock);
 *    atomic_val=op(*atomic_val, ...)
 *    unlock(atomic_lock);
 *
 *  -- andrei
 */

#endif /* __CPU_arm6 */


#endif