Annotation of qemu/qemu-lock.h, revision 1.1.1.2

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

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