/* * Portions Copyright 2008 VMware, Inc. */ #ifndef _X86_64_SEMAPHORE_H #define _X86_64_SEMAPHORE_H #include #ifdef __KERNEL__ /* * SMP- and interrupt-safe semaphores.. * * (C) Copyright 1996 Linus Torvalds * * Modified 1996-12-23 by Dave Grothe to fix bugs in * the original code and to make semaphore waits * interruptible so that processes waiting on * semaphores can be killed. * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper * functions in asm/sempahore-helper.h while fixing a * potential and subtle race discovered by Ulrich Schmid * in down_interruptible(). Since I started to play here I * also implemented the `trylock' semaphore operation. * 1999-07-02 Artur Skawina * Optimized "0(ecx)" -> "(ecx)" (the assembler does not * do this). Changed calling sequences from push/jmp to * traditional call/ret. * Modified 2001-01-01 Andreas Franck * Some hacks to ensure compatibility with recent * GCC snapshots, to avoid stack corruption when compiling * with -fomit-frame-pointer. It's not sure if this will * be fixed in GCC, as our previous implementation was a * bit dubious. * * If you would like to see an analysis of this implementation, please * ftp to gcom.com and download the file * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz. * */ #include #include #include #include #include #include #if defined(__VMKLNX__) #include "vmkapi.h" #endif /* defined(__VMKLNX__) */ struct semaphore { atomic_t count; int sleepers; wait_queue_head_t wait; }; /** * __SEMAPHORE_INITIALIZER - initialize the semaphore * @name: name of the semaphore * @n: count for the semaphore * * Initialize the semaphore and set its count to @n, the number of sleepers to * 0 and initialize its wait queue. * * RETURN VALUE: * This function does not return a value. */ /* _VMKLNX_CODECHECK_: __SEMAPHORE_INITIALIZER */ #define __SEMAPHORE_INITIALIZER(name, n) \ { \ .count = ATOMIC_INIT(n), \ .sleepers = 0, \ .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ } #define __DECLARE_SEMAPHORE_GENERIC(name,count) \ struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0) /** * sema_init - Initializes semaphore value * @sem: semaphore * @val: value * * Initilizes semaphore value * * RETURN VALUE: * NONE * */ /* _VMKLNX_CODECHECK_: sema_init */ static inline void sema_init (struct semaphore *sem, int val) { /* * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val); * * i'd rather use the more flexible initialization above, but sadly * GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well. */ atomic_set(&sem->count, val); sem->sleepers = 0; init_waitqueue_head(&sem->wait); } /** * init_MUTEX - Initializes the semaphore as free resource with exclusive access. * @sem: Pointer to semaphore * * The given semaphore is initialized as a free resource with exclusive * access. * * RETURN VALUE: * NONE * */ /* _VMKLNX_CODECHECK_: init_MUTEX */ static inline void init_MUTEX (struct semaphore *sem) { sema_init(sem, 1); } /** * init_MUTEX_LOCKED - Initializes the semaphore as busy resource with exclusive access. * @sem: Pointer to semaphore. * * The given semaphore is initialized as a busy resource with exclusive access * given to the caller of the initialization function. * * RETURN VALUE: * NONE */ /* _VMKLNX_CODECHECK_: init_MUTEX_LOCKED */ static inline void init_MUTEX_LOCKED (struct semaphore *sem) { sema_init(sem, 0); } asmlinkage void __down_failed(void /* special register calling convention */); asmlinkage int __down_failed_interruptible(void /* params in registers */); asmlinkage int __down_failed_trylock(void /* params in registers */); asmlinkage void __up_wakeup(void /* special register calling convention */); asmlinkage void __down(struct semaphore * sem); asmlinkage int __down_interruptible(struct semaphore * sem); asmlinkage int __down_trylock(struct semaphore * sem); asmlinkage void __up(struct semaphore * sem); /* * This is ugly, but we want the default case to fall through. * "__down_failed" is a special asm handler that calls the C * routine that actually waits. See arch/x86_64/kernel/semaphore.c */ /** * down - acquire a semaphore * @sem: Pointer to the semaphore to be acquired * * Acquires the specified semaphore. If the semaphore's count of available * acquisitions is exhausted, then the calling function will block. * * RETURN VALUE: * None */ /* _VMKLNX_CODECHECK_: down */ static inline void down(struct semaphore * sem) { might_sleep(); #if defined(__VMKLNX__) vmk_AtomicPrologue(); __asm__ __volatile__( "# atomic down operation\n\t" LOCK_PREFIX "decl %0\n\t" /* --sem->count */ "js 2f\n" "cmpb $0, vmk_AtomicUseFence(%%rip)\n" "jne 4f\n" "1:\n" LOCK_SECTION_START("") "2:\tcmpb $0, vmk_AtomicUseFence(%%rip)\n" "jne 3f\n" "call __down_failed\n\t" "jmp 1b\n" "3:\tlfence\n" "call __down_failed\n\t" "jmp 1b\n" "4:\tlfence\n" "jmp 1b\n" LOCK_SECTION_END :"=m" (sem->count) :"D" (sem) :"memory"); #else /* !defined(__VMKLNX__) */ __asm__ __volatile__( "# atomic down operation\n\t" LOCK_PREFIX "decl %0\n\t" /* --sem->count */ "js 2f\n" "1:\n" LOCK_SECTION_START("") "2:\tcall __down_failed\n\t" "jmp 1b\n" LOCK_SECTION_END :"=m" (sem->count) :"D" (sem) :"memory"); #endif /* !defined(__VMKLNX__) */ } /* * Interruptible try to acquire a semaphore. If we obtained * it, return zero. If we were interrupted, returns -EINTR */ /** * down_interruptible - Acquire a semaphore with an interruptible wait * @sem: Pointer to the semaphore to be acquired * * Attempt to acquire the specified semaphore. If the semaphore's count of available * acquisitions is exhausted, then the calling function will block. If a * signal is received by the blocking thread, then this function aborts. * * RETURN VALUE: * 0 on successful acquisition, or -EINTR if interrupted by a signal */ /* _VMKLNX_CODECHECK_: down_interruptible */ static inline int down_interruptible(struct semaphore * sem) { int result; might_sleep(); #if defined(__VMKLNX__) vmk_AtomicPrologue(); __asm__ __volatile__( "# atomic interruptible down operation\n\t" LOCK_PREFIX "decl %1\n\t" /* --sem->count */ "js 2f\n\t" "xorl %0,%0\n" "cmpb $0, vmk_AtomicUseFence(%%rip)\n\t" "jne 4f\n" "1:\n" LOCK_SECTION_START("") "2:\tcmpb $0, vmk_AtomicUseFence(%%rip)\n\t" "jne 3f\n" "call __down_failed_interruptible\n\t" "jmp 1b\n" "3:\tlfence\n" "call __down_failed_interruptible\n\t" "jmp 1b\n" "4:\tlfence\n" "jmp 1b\n" LOCK_SECTION_END :"=a" (result), "=m" (sem->count) :"D" (sem) :"memory"); #else /* !defined(__VMKLNX__) */ __asm__ __volatile__( "# atomic interruptible down operation\n\t" LOCK_PREFIX "decl %1\n\t" /* --sem->count */ "js 2f\n\t" "xorl %0,%0\n" "1:\n" LOCK_SECTION_START("") "2:\tcall __down_failed_interruptible\n\t" "jmp 1b\n" LOCK_SECTION_END :"=a" (result), "=m" (sem->count) :"D" (sem) :"memory"); #endif /* !defined(__VMKLNX__) */ return result; } /* * Non-blockingly attempt to down() a semaphore. * Returns zero if we acquired it */ /** * down_trylock - attempt to acquire a semaphore * @sem: Pointer to the semaphore to be acquired * * Attempt to acquire the specified semaphore. If the semaphore's count of available * acquisitions is exhausted, then return immediately. * * RETURN VALUE: * 0 on successful acquisition, or 1 if the semaphore is not immediately available */ /* _VMKLNX_CODECHECK_: down_trylock */ static inline int down_trylock(struct semaphore * sem) { int result; #if defined(__VMKLNX__) vmk_AtomicPrologue(); __asm__ __volatile__( "# atomic interruptible down operation\n\t" LOCK_PREFIX "decl %1\n\t" /* --sem->count */ "js 2f\n\t" "xorl %0,%0\n" "cmpb $0, vmk_AtomicUseFence(%%rip)\n\t" "jne 4f\n" "1:\n" LOCK_SECTION_START("") "2:\tcmpb $0, vmk_AtomicUseFence(%%rip)\n\t" "jne 3f\n" "call __down_failed_trylock\n\t" "jmp 1b\n" "3:\tlfence\n" "call __down_failed_trylock\n\t" "jmp 1b\n" "4:\tlfence\n" "jmp 1b\n" LOCK_SECTION_END :"=a" (result), "=m" (sem->count) :"D" (sem) :"memory","cc"); #else /* !defined(__VMKLNX__) */ __asm__ __volatile__( "# atomic interruptible down operation\n\t" LOCK_PREFIX "decl %1\n\t" /* --sem->count */ "js 2f\n\t" "xorl %0,%0\n" "1:\n" LOCK_SECTION_START("") "2:\tcall __down_failed_trylock\n\t" "jmp 1b\n" LOCK_SECTION_END :"=a" (result), "=m" (sem->count) :"D" (sem) :"memory","cc"); #endif /* !defined(__VMKLNX__) */ return result; } /* * Note! This is subtle. We jump to wake people up only if * the semaphore was negative (== somebody was waiting on it). * The default case (no contention) will result in NO * jumps for both down() and up(). */ /** * up - release semaphore * @sem: pointer to initialized and acquired semaphore * * RETURN VALUE: * none */ /* _VMKLNX_CODECHECK_: up */ static inline void up(struct semaphore * sem) { #if defined(__VMKLNX__) vmk_AtomicPrologue(); __asm__ __volatile__( "# atomic up operation\n\t" LOCK_PREFIX "incl %0\n\t" /* ++sem->count */ "jle 2f\n" "cmpb $0, vmk_AtomicUseFence(%%rip)\n\t" "jne 4f\n" "1:\n" LOCK_SECTION_START("") "2:\tcmpb $0, vmk_AtomicUseFence(%%rip)\n\t" "jne 3f\n" "call __up_wakeup\n\t" "jmp 1b\n" "3:\tlfence\n" "call __up_wakeup\n\t" "jmp 1b\n" "4:\tlfence\n" "jmp 1b\n" LOCK_SECTION_END :"=m" (sem->count) :"D" (sem) :"memory"); #else /* !defined(__VMKLNX__) */ __asm__ __volatile__( "# atomic up operation\n\t" LOCK_PREFIX "incl %0\n\t" /* ++sem->count */ "jle 2f\n" "1:\n" LOCK_SECTION_START("") "2:\tcall __up_wakeup\n\t" "jmp 1b\n" LOCK_SECTION_END :"=m" (sem->count) :"D" (sem) :"memory"); #endif /* !defined(__VMKLNX__) */ } #endif /* __KERNEL__ */ #endif