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