include/asm-i386/semaphore.h

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