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Annotation of Gnu-Mach/linux/src/include/asm-i386/semaphore.h, revision 1.1

1.1     ! root        1: #ifndef _I386_SEMAPHORE_H
        !             2: #define _I386_SEMAPHORE_H
        !             3: 
        !             4: #include <linux/linkage.h>
        !             5: #include <asm/system.h>
        !             6: 
        !             7: /*
        !             8:  * SMP- and interrupt-safe semaphores..
        !             9:  *
        !            10:  * (C) Copyright 1996 Linus Torvalds
        !            11:  *
        !            12:  * Modified 1996-12-23 by Dave Grothe <[email protected]> to fix bugs in
        !            13:  *                     the original code and to make semaphore waits
        !            14:  *                     interruptible so that processes waiting on
        !            15:  *                     semaphores can be killed.
        !            16:  *
        !            17:  * If you would like to see an analysis of this implementation, please
        !            18:  * ftp to gcom.com and download the file
        !            19:  * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz.
        !            20:  *
        !            21:  */
        !            22: 
        !            23: struct semaphore {
        !            24:        int count;
        !            25:        int waking;
        !            26:        int lock ;                      /* to make waking testing atomic */
        !            27:        struct wait_queue * wait;
        !            28: };
        !            29: 
        !            30: #define MUTEX ((struct semaphore) { 1, 0, 0, NULL })
        !            31: #define MUTEX_LOCKED ((struct semaphore) { 0, 0, 0, NULL })
        !            32: 
        !            33: asmlinkage void down_failed(void /* special register calling convention */);
        !            34: asmlinkage void up_wakeup(void /* special register calling convention */);
        !            35: 
        !            36: extern void __down(struct semaphore * sem);
        !            37: extern void __up(struct semaphore * sem);
        !            38: 
        !            39: /*
        !            40:  * This is ugly, but we want the default case to fall through.
        !            41:  * "down_failed" is a special asm handler that calls the C
        !            42:  * routine that actually waits. See arch/i386/lib/semaphore.S
        !            43:  */
        !            44: extern inline void down(struct semaphore * sem)
        !            45: {
        !            46:        __asm__ __volatile__(
        !            47:                "# atomic down operation\n\t"
        !            48:                "movl $1f,%%eax\n\t"
        !            49: #ifdef __SMP__
        !            50:                "lock ; "
        !            51: #endif
        !            52:                "decl 0(%0)\n\t"
        !            53:                "js " SYMBOL_NAME_STR(down_failed) "\n"
        !            54:                "1:\n"
        !            55:                :/* no outputs */
        !            56:                :"c" (sem)
        !            57:                :"ax","dx","memory");
        !            58: }
        !            59: 
        !            60: /*
        !            61:  * Primitives to spin on a lock.  Needed only for SMP version.
        !            62:  */
        !            63: extern inline void get_buzz_lock(int *lock_ptr)
        !            64: {
        !            65: #ifdef __SMP__
        !            66:         while (xchg(lock_ptr,1) != 0) ;
        !            67: #endif
        !            68: } /* get_buzz_lock */
        !            69: 
        !            70: extern inline void give_buzz_lock(int *lock_ptr)
        !            71: {
        !            72: #ifdef __SMP__
        !            73:         *lock_ptr = 0 ;
        !            74: #endif
        !            75: } /* give_buzz_lock */
        !            76: 
        !            77: asmlinkage int down_failed_interruptible(void);  /* params in registers */
        !            78: 
        !            79: /*
        !            80:  * This version waits in interruptible state so that the waiting
        !            81:  * process can be killed.  The down_failed_interruptible routine
        !            82:  * returns negative for signalled and zero for semaphore acquired.
        !            83:  */
        !            84: extern inline int down_interruptible(struct semaphore * sem)
        !            85: {
        !            86:        int     ret ;
        !            87: 
        !            88:         __asm__ __volatile__(
        !            89:                 "# atomic interruptible down operation\n\t"
        !            90:                 "movl $2f,%%eax\n\t"
        !            91: #ifdef __SMP__
        !            92:                 "lock ; "
        !            93: #endif
        !            94:                 "decl 0(%1)\n\t"
        !            95:                 "js " SYMBOL_NAME_STR(down_failed_interruptible) "\n\t"
        !            96:                 "xorl %%eax,%%eax\n"
        !            97:                 "2:\n"
        !            98:                 :"=a" (ret)
        !            99:                 :"c" (sem)
        !           100:                 :"ax","dx","memory");
        !           101: 
        !           102:        return(ret) ;
        !           103: }
        !           104: 
        !           105: /*
        !           106:  * Note! This is subtle. We jump to wake people up only if
        !           107:  * the semaphore was negative (== somebody was waiting on it).
        !           108:  * The default case (no contention) will result in NO
        !           109:  * jumps for both down() and up().
        !           110:  */
        !           111: extern inline void up(struct semaphore * sem)
        !           112: {
        !           113:        __asm__ __volatile__(
        !           114:                "# atomic up operation\n\t"
        !           115:                "movl $1f,%%eax\n\t"
        !           116: #ifdef __SMP__
        !           117:                "lock ; "
        !           118: #endif
        !           119:                "incl 0(%0)\n\t"
        !           120:                "jle " SYMBOL_NAME_STR(up_wakeup)
        !           121:                "\n1:"
        !           122:                :/* no outputs */
        !           123:                :"c" (sem)
        !           124:                :"ax", "dx", "memory");
        !           125: }
        !           126: 
        !           127: #endif

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