Annotation of qemu/qemu-lock.h, revision 1.1.1.1

1.1       root        1: /*
                      2:  *  Copyright (c) 2003 Fabrice Bellard
                      3:  *
                      4:  * This library is free software; you can redistribute it and/or
                      5:  * modify it under the terms of the GNU Lesser General Public
                      6:  * License as published by the Free Software Foundation; either
                      7:  * version 2 of the License, or (at your option) any later version.
                      8:  *
                      9:  * This library is distributed in the hope that it will be useful,
                     10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
                     11:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
                     12:  * Lesser General Public License for more details.
                     13:  *
                     14:  * You should have received a copy of the GNU Lesser General Public
                     15:  * License along with this library; if not, write to the Free Software
                     16:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA  02110-1301 USA
                     17:  */
                     18: 
                     19: /* Locking primitives.  Most of this code should be redundant -
                     20:    system emulation doesn't need/use locking, NPTL userspace uses
                     21:    pthread mutexes, and non-NPTL userspace isn't threadsafe anyway.
                     22:    In either case a spinlock is probably the wrong kind of lock.
                     23:    Spinlocks are only good if you know annother CPU has the lock and is
                     24:    likely to release it soon.  In environments where you have more threads
                     25:    than physical CPUs (the extreme case being a single CPU host) a spinlock
                     26:    simply wastes CPU until the OS decides to preempt it.  */
                     27: #if defined(USE_NPTL)
                     28: 
                     29: #include <pthread.h>
                     30: #define spin_lock pthread_mutex_lock
                     31: #define spin_unlock pthread_mutex_unlock
                     32: #define spinlock_t pthread_mutex_t
                     33: #define SPIN_LOCK_UNLOCKED PTHREAD_MUTEX_INITIALIZER
                     34: 
                     35: #else
                     36: 
                     37: #if defined(__hppa__)
                     38: 
                     39: typedef int spinlock_t[4];
                     40: 
                     41: #define SPIN_LOCK_UNLOCKED { 1, 1, 1, 1 }
                     42: 
                     43: static inline void resetlock (spinlock_t *p)
                     44: {
                     45:     (*p)[0] = (*p)[1] = (*p)[2] = (*p)[3] = 1;
                     46: }
                     47: 
                     48: #else
                     49: 
                     50: typedef int spinlock_t;
                     51: 
                     52: #define SPIN_LOCK_UNLOCKED 0
                     53: 
                     54: static inline void resetlock (spinlock_t *p)
                     55: {
                     56:     *p = SPIN_LOCK_UNLOCKED;
                     57: }
                     58: 
                     59: #endif
                     60: 
                     61: #if defined(_ARCH_PPC)
                     62: static inline int testandset (int *p)
                     63: {
                     64:     int ret;
                     65:     __asm__ __volatile__ (
                     66:                           "      lwarx %0,0,%1\n"
                     67:                           "      xor. %0,%3,%0\n"
                     68:                           "      bne $+12\n"
                     69:                           "      stwcx. %2,0,%1\n"
                     70:                           "      bne- $-16\n"
                     71:                           : "=&r" (ret)
                     72:                           : "r" (p), "r" (1), "r" (0)
                     73:                           : "cr0", "memory");
                     74:     return ret;
                     75: }
                     76: #elif defined(__i386__)
                     77: static inline int testandset (int *p)
                     78: {
                     79:     long int readval = 0;
                     80: 
                     81:     __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
                     82:                           : "+m" (*p), "+a" (readval)
                     83:                           : "r" (1)
                     84:                           : "cc");
                     85:     return readval;
                     86: }
                     87: #elif defined(__x86_64__)
                     88: static inline int testandset (int *p)
                     89: {
                     90:     long int readval = 0;
                     91: 
                     92:     __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
                     93:                           : "+m" (*p), "+a" (readval)
                     94:                           : "r" (1)
                     95:                           : "cc");
                     96:     return readval;
                     97: }
                     98: #elif defined(__s390__)
                     99: static inline int testandset (int *p)
                    100: {
                    101:     int ret;
                    102: 
                    103:     __asm__ __volatile__ ("0: cs    %0,%1,0(%2)\n"
                    104:                          "   jl    0b"
                    105:                          : "=&d" (ret)
                    106:                          : "r" (1), "a" (p), "0" (*p)
                    107:                          : "cc", "memory" );
                    108:     return ret;
                    109: }
                    110: #elif defined(__alpha__)
                    111: static inline int testandset (int *p)
                    112: {
                    113:     int ret;
                    114:     unsigned long one;
                    115: 
                    116:     __asm__ __volatile__ ("0:  mov 1,%2\n"
                    117:                          "     ldl_l %0,%1\n"
                    118:                          "     stl_c %2,%1\n"
                    119:                          "     beq %2,1f\n"
                    120:                          ".subsection 2\n"
                    121:                          "1:   br 0b\n"
                    122:                          ".previous"
                    123:                          : "=r" (ret), "=m" (*p), "=r" (one)
                    124:                          : "m" (*p));
                    125:     return ret;
                    126: }
                    127: #elif defined(__sparc__)
                    128: static inline int testandset (int *p)
                    129: {
                    130:        int ret;
                    131: 
                    132:        __asm__ __volatile__("ldstub    [%1], %0"
                    133:                             : "=r" (ret)
                    134:                             : "r" (p)
                    135:                             : "memory");
                    136: 
                    137:        return (ret ? 1 : 0);
                    138: }
                    139: #elif defined(__arm__)
                    140: static inline int testandset (int *spinlock)
                    141: {
                    142:     register unsigned int ret;
                    143:     __asm__ __volatile__("swp %0, %1, [%2]"
                    144:                          : "=r"(ret)
                    145:                          : "0"(1), "r"(spinlock));
                    146: 
                    147:     return ret;
                    148: }
                    149: #elif defined(__mc68000)
                    150: static inline int testandset (int *p)
                    151: {
                    152:     char ret;
                    153:     __asm__ __volatile__("tas %1; sne %0"
                    154:                          : "=r" (ret)
                    155:                          : "m" (p)
                    156:                          : "cc","memory");
                    157:     return ret;
                    158: }
                    159: #elif defined(__hppa__)
                    160: 
                    161: /* Because malloc only guarantees 8-byte alignment for malloc'd data,
                    162:    and GCC only guarantees 8-byte alignment for stack locals, we can't
                    163:    be assured of 16-byte alignment for atomic lock data even if we
                    164:    specify "__attribute ((aligned(16)))" in the type declaration.  So,
                    165:    we use a struct containing an array of four ints for the atomic lock
                    166:    type and dynamically select the 16-byte aligned int from the array
                    167:    for the semaphore.  */
                    168: #define __PA_LDCW_ALIGNMENT 16
                    169: static inline void *ldcw_align (void *p) {
                    170:     unsigned long a = (unsigned long)p;
                    171:     a = (a + __PA_LDCW_ALIGNMENT - 1) & ~(__PA_LDCW_ALIGNMENT - 1);
                    172:     return (void *)a;
                    173: }
                    174: 
                    175: static inline int testandset (spinlock_t *p)
                    176: {
                    177:     unsigned int ret;
                    178:     p = ldcw_align(p);
                    179:     __asm__ __volatile__("ldcw 0(%1),%0"
                    180:                          : "=r" (ret)
                    181:                          : "r" (p)
                    182:                          : "memory" );
                    183:     return !ret;
                    184: }
                    185: 
                    186: #elif defined(__ia64)
                    187: 
                    188: #include <ia64intrin.h>
                    189: 
                    190: static inline int testandset (int *p)
                    191: {
                    192:     return __sync_lock_test_and_set (p, 1);
                    193: }
                    194: #elif defined(__mips__)
                    195: static inline int testandset (int *p)
                    196: {
                    197:     int ret;
                    198: 
                    199:     __asm__ __volatile__ (
                    200:        "       .set push               \n"
                    201:        "       .set noat               \n"
                    202:        "       .set mips2              \n"
                    203:        "1:     li      $1, 1           \n"
                    204:        "       ll      %0, %1          \n"
                    205:        "       sc      $1, %1          \n"
                    206:        "       beqz    $1, 1b          \n"
                    207:        "       .set pop                "
                    208:        : "=r" (ret), "+R" (*p)
                    209:        :
                    210:        : "memory");
                    211: 
                    212:     return ret;
                    213: }
                    214: #else
                    215: #error unimplemented CPU support
                    216: #endif
                    217: 
                    218: #if defined(CONFIG_USER_ONLY)
                    219: static inline void spin_lock(spinlock_t *lock)
                    220: {
                    221:     while (testandset(lock));
                    222: }
                    223: 
                    224: static inline void spin_unlock(spinlock_t *lock)
                    225: {
                    226:     resetlock(lock);
                    227: }
                    228: 
                    229: static inline int spin_trylock(spinlock_t *lock)
                    230: {
                    231:     return !testandset(lock);
                    232: }
                    233: #else
                    234: static inline void spin_lock(spinlock_t *lock)
                    235: {
                    236: }
                    237: 
                    238: static inline void spin_unlock(spinlock_t *lock)
                    239: {
                    240: }
                    241: 
                    242: static inline int spin_trylock(spinlock_t *lock)
                    243: {
                    244:     return 1;
                    245: }
                    246: #endif
                    247: 
                    248: #endif

unix.superglobalmegacorp.com