The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/i386/include/atomic.h

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    1 /*-
    2  * Copyright (c) 1998 Doug Rabson
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  *
   26  * $FreeBSD$
   27  */
   28 #ifndef _MACHINE_ATOMIC_H_
   29 #define _MACHINE_ATOMIC_H_
   30 
   31 #ifndef _SYS_CDEFS_H_
   32 #error this file needs sys/cdefs.h as a prerequisite
   33 #endif
   34 
   35 /*
   36  * Various simple arithmetic on memory which is atomic in the presence
   37  * of interrupts and multiple processors.
   38  *
   39  * atomic_set_char(P, V)        (*(u_char*)(P) |= (V))
   40  * atomic_clear_char(P, V)      (*(u_char*)(P) &= ~(V))
   41  * atomic_add_char(P, V)        (*(u_char*)(P) += (V))
   42  * atomic_subtract_char(P, V)   (*(u_char*)(P) -= (V))
   43  *
   44  * atomic_set_short(P, V)       (*(u_short*)(P) |= (V))
   45  * atomic_clear_short(P, V)     (*(u_short*)(P) &= ~(V))
   46  * atomic_add_short(P, V)       (*(u_short*)(P) += (V))
   47  * atomic_subtract_short(P, V)  (*(u_short*)(P) -= (V))
   48  *
   49  * atomic_set_int(P, V)         (*(u_int*)(P) |= (V))
   50  * atomic_clear_int(P, V)       (*(u_int*)(P) &= ~(V))
   51  * atomic_add_int(P, V)         (*(u_int*)(P) += (V))
   52  * atomic_subtract_int(P, V)    (*(u_int*)(P) -= (V))
   53  * atomic_readandclear_int(P)   (return  *(u_int*)P; *(u_int*)P = 0;)
   54  *
   55  * atomic_set_long(P, V)        (*(u_long*)(P) |= (V))
   56  * atomic_clear_long(P, V)      (*(u_long*)(P) &= ~(V))
   57  * atomic_add_long(P, V)        (*(u_long*)(P) += (V))
   58  * atomic_subtract_long(P, V)   (*(u_long*)(P) -= (V))
   59  * atomic_readandclear_long(P)  (return  *(u_long*)P; *(u_long*)P = 0;)
   60  */
   61 
   62 /*
   63  * The above functions are expanded inline in the statically-linked
   64  * kernel.  Lock prefixes are generated if an SMP kernel is being
   65  * built.
   66  *
   67  * Kernel modules call real functions which are built into the kernel.
   68  * This allows kernel modules to be portable between UP and SMP systems.
   69  */
   70 #if defined(KLD_MODULE) || !defined(__GNUCLIKE_ASM)
   71 #define ATOMIC_ASM(NAME, TYPE, OP, CONS, V)                     \
   72 void atomic_##NAME##_##TYPE(volatile u_##TYPE *p, u_##TYPE v)
   73 
   74 int atomic_cmpset_int(volatile u_int *dst, u_int exp, u_int src);
   75 u_int atomic_fetchadd_int(volatile u_int *p, u_int v);
   76 
   77 #define ATOMIC_STORE_LOAD(TYPE, LOP, SOP)                       \
   78 u_##TYPE        atomic_load_acq_##TYPE(volatile u_##TYPE *p);   \
   79 void            atomic_store_rel_##TYPE(volatile u_##TYPE *p, u_##TYPE v)
   80 
   81 #else /* !KLD_MODULE && __GNUCLIKE_ASM */
   82 
   83 /*
   84  * For userland, assume the SMP case and use lock prefixes so that
   85  * the binaries will run on both types of systems.
   86  */
   87 #if defined(SMP) || !defined(_KERNEL)
   88 #define MPLOCKED        lock ;
   89 #else
   90 #define MPLOCKED
   91 #endif
   92 
   93 /*
   94  * The assembly is volatilized to demark potential before-and-after side
   95  * effects if an interrupt or SMP collision were to occur.
   96  */
   97 #define ATOMIC_ASM(NAME, TYPE, OP, CONS, V)             \
   98 static __inline void                                    \
   99 atomic_##NAME##_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
  100 {                                                       \
  101         __asm __volatile(__XSTRING(MPLOCKED) OP         \
  102                          : "=m" (*p)                    \
  103                          : CONS (V), "m" (*p));         \
  104 }                                                       \
  105 struct __hack
  106 
  107 /*
  108  * Atomic compare and set, used by the mutex functions
  109  *
  110  * if (*dst == exp) *dst = src (all 32 bit words)
  111  *
  112  * Returns 0 on failure, non-zero on success
  113  */
  114 
  115 #if defined(CPU_DISABLE_CMPXCHG)
  116 
  117 static __inline int
  118 atomic_cmpset_int(volatile u_int *dst, u_int exp, u_int src)
  119 {
  120         int res = exp;
  121 
  122         __asm __volatile(
  123         "       pushfl ;                "
  124         "       cli ;                   "
  125         "       cmpl    %0,%3 ;         "
  126         "       jne     1f ;            "
  127         "       movl    %2,%1 ;         "
  128         "1:                             "
  129         "       sete    %%al;           "
  130         "       movzbl  %%al,%0 ;       "
  131         "       popfl ;                 "
  132         "# atomic_cmpset_int"
  133         : "+a" (res),                   /* 0 (result) */
  134           "=m" (*dst)                   /* 1 */
  135         : "r" (src),                    /* 2 */
  136           "m" (*dst)                    /* 3 */
  137         : "memory");
  138 
  139         return (res);
  140 }
  141 
  142 #else /* defined(CPU_DISABLE_CMPXCHG) */
  143 
  144 static __inline int
  145 atomic_cmpset_int(volatile u_int *dst, u_int exp, u_int src)
  146 {
  147         int res = exp;
  148 
  149         __asm __volatile (
  150         "       " __XSTRING(MPLOCKED) " "
  151         "       cmpxchgl %2,%1 ;        "
  152         "       setz    %%al ;          "
  153         "       movzbl  %%al,%0 ;       "
  154         "1:                             "
  155         "# atomic_cmpset_int"
  156         : "+a" (res),                   /* 0 (result) */
  157           "=m" (*dst)                   /* 1 */
  158         : "r" (src),                    /* 2 */
  159           "m" (*dst)                    /* 3 */
  160         : "memory");
  161 
  162         return (res);
  163 }
  164 
  165 #endif /* defined(CPU_DISABLE_CMPXCHG) */
  166 
  167 /*
  168  * Atomically add the value of v to the integer pointed to by p and return
  169  * the previous value of *p.
  170  */
  171 static __inline u_int
  172 atomic_fetchadd_int(volatile u_int *p, u_int v)
  173 {
  174 
  175         __asm __volatile (
  176         "       " __XSTRING(MPLOCKED) " "
  177         "       xaddl   %0, %1 ;        "
  178         "# atomic_fetchadd_int"
  179         : "+r" (v),                     /* 0 (result) */
  180           "=m" (*p)                     /* 1 */
  181         : "m" (*p));                    /* 2 */
  182 
  183         return (v);
  184 }
  185 
  186 #if defined(_KERNEL) && !defined(SMP)
  187 
  188 /*
  189  * We assume that a = b will do atomic loads and stores.  However, on a
  190  * PentiumPro or higher, reads may pass writes, so for that case we have
  191  * to use a serializing instruction (i.e. with LOCK) to do the load in
  192  * SMP kernels.  For UP kernels, however, the cache of the single processor
  193  * is always consistent, so we don't need any memory barriers.
  194  */
  195 #define ATOMIC_STORE_LOAD(TYPE, LOP, SOP)               \
  196 static __inline u_##TYPE                                \
  197 atomic_load_acq_##TYPE(volatile u_##TYPE *p)            \
  198 {                                                       \
  199         return (*p);                                    \
  200 }                                                       \
  201                                                         \
  202 static __inline void                                    \
  203 atomic_store_rel_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
  204 {                                                       \
  205         *p = v;                                         \
  206 }                                                       \
  207 struct __hack
  208 
  209 #else /* defined(SMP) */
  210 
  211 #define ATOMIC_STORE_LOAD(TYPE, LOP, SOP)               \
  212 static __inline u_##TYPE                                \
  213 atomic_load_acq_##TYPE(volatile u_##TYPE *p)            \
  214 {                                                       \
  215         u_##TYPE res;                                   \
  216                                                         \
  217         __asm __volatile(__XSTRING(MPLOCKED) LOP        \
  218         : "=a" (res),                   /* 0 (result) */\
  219           "=m" (*p)                     /* 1 */         \
  220         : "m" (*p)                      /* 2 */         \
  221         : "memory");                                    \
  222                                                         \
  223         return (res);                                   \
  224 }                                                       \
  225                                                         \
  226 /*                                                      \
  227  * The XCHG instruction asserts LOCK automagically.     \
  228  */                                                     \
  229 static __inline void                                    \
  230 atomic_store_rel_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
  231 {                                                       \
  232         __asm __volatile(SOP                            \
  233         : "=m" (*p),                    /* 0 */         \
  234           "+r" (v)                      /* 1 */         \
  235         : "m" (*p));                    /* 2 */         \
  236 }                                                       \
  237 struct __hack
  238 
  239 #endif  /* !defined(SMP) */
  240 
  241 #endif /* KLD_MODULE || !__GNUCLIKE_ASM */
  242 
  243 ATOMIC_ASM(set,      char,  "orb %b1,%0",  "iq",  v);
  244 ATOMIC_ASM(clear,    char,  "andb %b1,%0", "iq", ~v);
  245 ATOMIC_ASM(add,      char,  "addb %b1,%0", "iq",  v);
  246 ATOMIC_ASM(subtract, char,  "subb %b1,%0", "iq",  v);
  247 
  248 ATOMIC_ASM(set,      short, "orw %w1,%0",  "ir",  v);
  249 ATOMIC_ASM(clear,    short, "andw %w1,%0", "ir", ~v);
  250 ATOMIC_ASM(add,      short, "addw %w1,%0", "ir",  v);
  251 ATOMIC_ASM(subtract, short, "subw %w1,%0", "ir",  v);
  252 
  253 ATOMIC_ASM(set,      int,   "orl %1,%0",   "ir",  v);
  254 ATOMIC_ASM(clear,    int,   "andl %1,%0",  "ir", ~v);
  255 ATOMIC_ASM(add,      int,   "addl %1,%0",  "ir",  v);
  256 ATOMIC_ASM(subtract, int,   "subl %1,%0",  "ir",  v);
  257 
  258 ATOMIC_ASM(set,      long,  "orl %1,%0",   "ir",  v);
  259 ATOMIC_ASM(clear,    long,  "andl %1,%0",  "ir", ~v);
  260 ATOMIC_ASM(add,      long,  "addl %1,%0",  "ir",  v);
  261 ATOMIC_ASM(subtract, long,  "subl %1,%0",  "ir",  v);
  262 
  263 ATOMIC_STORE_LOAD(char, "cmpxchgb %b0,%1", "xchgb %b1,%0");
  264 ATOMIC_STORE_LOAD(short,"cmpxchgw %w0,%1", "xchgw %w1,%0");
  265 ATOMIC_STORE_LOAD(int,  "cmpxchgl %0,%1",  "xchgl %1,%0");
  266 ATOMIC_STORE_LOAD(long, "cmpxchgl %0,%1",  "xchgl %1,%0");
  267 
  268 #undef ATOMIC_ASM
  269 #undef ATOMIC_STORE_LOAD
  270 
  271 #if !defined(WANT_FUNCTIONS)
  272 
  273 static __inline int
  274 atomic_cmpset_long(volatile u_long *dst, u_long exp, u_long src)
  275 {
  276 
  277         return (atomic_cmpset_int((volatile u_int *)dst, (u_int)exp,
  278             (u_int)src));
  279 }
  280 
  281 /* Read the current value and store a zero in the destination. */
  282 #ifdef __GNUCLIKE_ASM
  283 
  284 static __inline u_int
  285 atomic_readandclear_int(volatile u_int *addr)
  286 {
  287         u_int result;
  288 
  289         result = 0;
  290         __asm __volatile (
  291         "       xchgl   %1,%0 ;         "
  292         "# atomic_readandclear_int"
  293         : "+r" (result),                /* 0 (result) */
  294           "=m" (*addr)                  /* 1 (addr) */
  295         : "m" (*addr));
  296 
  297         return (result);
  298 }
  299 
  300 static __inline u_long
  301 atomic_readandclear_long(volatile u_long *addr)
  302 {
  303         u_long result;
  304 
  305         result = 0;
  306         __asm __volatile (
  307         "       xchgl   %1,%0 ;         "
  308         "# atomic_readandclear_long"
  309         : "+r" (result),                /* 0 (result) */
  310           "=m" (*addr)                  /* 1 (addr) */
  311         : "m" (*addr));
  312 
  313         return (result);
  314 }
  315 
  316 #else /* !__GNUCLIKE_ASM */
  317 
  318 u_int   atomic_readandclear_int(volatile u_int *);
  319 u_long  atomic_readandclear_long(volatile u_long *);
  320 
  321 #endif /* __GNUCLIKE_ASM */
  322 
  323 /* Acquire and release variants are identical to the normal ones. */
  324 #define atomic_set_acq_char             atomic_set_char
  325 #define atomic_set_rel_char             atomic_set_char
  326 #define atomic_clear_acq_char           atomic_clear_char
  327 #define atomic_clear_rel_char           atomic_clear_char
  328 #define atomic_add_acq_char             atomic_add_char
  329 #define atomic_add_rel_char             atomic_add_char
  330 #define atomic_subtract_acq_char        atomic_subtract_char
  331 #define atomic_subtract_rel_char        atomic_subtract_char
  332 
  333 #define atomic_set_acq_short            atomic_set_short
  334 #define atomic_set_rel_short            atomic_set_short
  335 #define atomic_clear_acq_short          atomic_clear_short
  336 #define atomic_clear_rel_short          atomic_clear_short
  337 #define atomic_add_acq_short            atomic_add_short
  338 #define atomic_add_rel_short            atomic_add_short
  339 #define atomic_subtract_acq_short       atomic_subtract_short
  340 #define atomic_subtract_rel_short       atomic_subtract_short
  341 
  342 #define atomic_set_acq_int              atomic_set_int
  343 #define atomic_set_rel_int              atomic_set_int
  344 #define atomic_clear_acq_int            atomic_clear_int
  345 #define atomic_clear_rel_int            atomic_clear_int
  346 #define atomic_add_acq_int              atomic_add_int
  347 #define atomic_add_rel_int              atomic_add_int
  348 #define atomic_subtract_acq_int         atomic_subtract_int
  349 #define atomic_subtract_rel_int         atomic_subtract_int
  350 #define atomic_cmpset_acq_int           atomic_cmpset_int
  351 #define atomic_cmpset_rel_int           atomic_cmpset_int
  352 
  353 #define atomic_set_acq_long             atomic_set_long
  354 #define atomic_set_rel_long             atomic_set_long
  355 #define atomic_clear_acq_long           atomic_clear_long
  356 #define atomic_clear_rel_long           atomic_clear_long
  357 #define atomic_add_acq_long             atomic_add_long
  358 #define atomic_add_rel_long             atomic_add_long
  359 #define atomic_subtract_acq_long        atomic_subtract_long
  360 #define atomic_subtract_rel_long        atomic_subtract_long
  361 #define atomic_cmpset_acq_long          atomic_cmpset_long
  362 #define atomic_cmpset_rel_long          atomic_cmpset_long
  363 
  364 /* Operations on 8-bit bytes. */
  365 #define atomic_set_8            atomic_set_char
  366 #define atomic_set_acq_8        atomic_set_acq_char
  367 #define atomic_set_rel_8        atomic_set_rel_char
  368 #define atomic_clear_8          atomic_clear_char
  369 #define atomic_clear_acq_8      atomic_clear_acq_char
  370 #define atomic_clear_rel_8      atomic_clear_rel_char
  371 #define atomic_add_8            atomic_add_char
  372 #define atomic_add_acq_8        atomic_add_acq_char
  373 #define atomic_add_rel_8        atomic_add_rel_char
  374 #define atomic_subtract_8       atomic_subtract_char
  375 #define atomic_subtract_acq_8   atomic_subtract_acq_char
  376 #define atomic_subtract_rel_8   atomic_subtract_rel_char
  377 #define atomic_load_acq_8       atomic_load_acq_char
  378 #define atomic_store_rel_8      atomic_store_rel_char
  379 
  380 /* Operations on 16-bit words. */
  381 #define atomic_set_16           atomic_set_short
  382 #define atomic_set_acq_16       atomic_set_acq_short
  383 #define atomic_set_rel_16       atomic_set_rel_short
  384 #define atomic_clear_16         atomic_clear_short
  385 #define atomic_clear_acq_16     atomic_clear_acq_short
  386 #define atomic_clear_rel_16     atomic_clear_rel_short
  387 #define atomic_add_16           atomic_add_short
  388 #define atomic_add_acq_16       atomic_add_acq_short
  389 #define atomic_add_rel_16       atomic_add_rel_short
  390 #define atomic_subtract_16      atomic_subtract_short
  391 #define atomic_subtract_acq_16  atomic_subtract_acq_short
  392 #define atomic_subtract_rel_16  atomic_subtract_rel_short
  393 #define atomic_load_acq_16      atomic_load_acq_short
  394 #define atomic_store_rel_16     atomic_store_rel_short
  395 
  396 /* Operations on 32-bit double words. */
  397 #define atomic_set_32           atomic_set_int
  398 #define atomic_set_acq_32       atomic_set_acq_int
  399 #define atomic_set_rel_32       atomic_set_rel_int
  400 #define atomic_clear_32         atomic_clear_int
  401 #define atomic_clear_acq_32     atomic_clear_acq_int
  402 #define atomic_clear_rel_32     atomic_clear_rel_int
  403 #define atomic_add_32           atomic_add_int
  404 #define atomic_add_acq_32       atomic_add_acq_int
  405 #define atomic_add_rel_32       atomic_add_rel_int
  406 #define atomic_subtract_32      atomic_subtract_int
  407 #define atomic_subtract_acq_32  atomic_subtract_acq_int
  408 #define atomic_subtract_rel_32  atomic_subtract_rel_int
  409 #define atomic_load_acq_32      atomic_load_acq_int
  410 #define atomic_store_rel_32     atomic_store_rel_int
  411 #define atomic_cmpset_32        atomic_cmpset_int
  412 #define atomic_cmpset_acq_32    atomic_cmpset_acq_int
  413 #define atomic_cmpset_rel_32    atomic_cmpset_rel_int
  414 #define atomic_readandclear_32  atomic_readandclear_int
  415 #define atomic_fetchadd_32      atomic_fetchadd_int
  416 
  417 /* Operations on pointers. */
  418 #define atomic_set_ptr          atomic_set_int
  419 #define atomic_set_acq_ptr      atomic_set_acq_int
  420 #define atomic_set_rel_ptr      atomic_set_rel_int
  421 #define atomic_clear_ptr        atomic_clear_int
  422 #define atomic_clear_acq_ptr    atomic_clear_acq_int
  423 #define atomic_clear_rel_ptr    atomic_clear_rel_int
  424 #define atomic_add_ptr          atomic_add_int
  425 #define atomic_add_acq_ptr      atomic_add_acq_int
  426 #define atomic_add_rel_ptr      atomic_add_rel_int
  427 #define atomic_subtract_ptr     atomic_subtract_int
  428 #define atomic_subtract_acq_ptr atomic_subtract_acq_int
  429 #define atomic_subtract_rel_ptr atomic_subtract_rel_int
  430 #define atomic_load_acq_ptr     atomic_load_acq_int
  431 #define atomic_store_rel_ptr    atomic_store_rel_int
  432 #define atomic_cmpset_ptr       atomic_cmpset_int
  433 #define atomic_cmpset_acq_ptr   atomic_cmpset_acq_int
  434 #define atomic_cmpset_rel_ptr   atomic_cmpset_rel_int
  435 #define atomic_readandclear_ptr atomic_readandclear_int
  436 
  437 #endif  /* !defined(WANT_FUNCTIONS) */
  438 #endif /* ! _MACHINE_ATOMIC_H_ */

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