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87 lines
2.8 KiB
C
87 lines
2.8 KiB
C
/*
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* Mutexes: blocking mutual exclusion locks
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*
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* started by Ingo Molnar:
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*
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* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*
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* This file contains the main data structure and API definitions.
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*/
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#ifndef __LINUX_MUTEX_H
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#define __LINUX_MUTEX_H
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#include <linux/list.h>
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#include <asm/atomic.h>
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/*
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* Simple, straightforward mutexes with strict semantics:
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*
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* - only one task can hold the mutex at a time
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* - only the owner can unlock the mutex
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* - multiple unlocks are not permitted
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* - recursive locking is not permitted
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* - a mutex object must be initialized via the API
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* - a mutex object must not be initialized via memset or copying
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* - task may not exit with mutex held
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* - memory areas where held locks reside must not be freed
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* - held mutexes must not be reinitialized
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* - mutexes may not be used in hardware or software interrupt
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* contexts such as tasklets and timers
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*
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* These semantics are fully enforced when DEBUG_MUTEXES is
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* enabled. Furthermore, besides enforcing the above rules, the mutex
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* debugging code also implements a number of additional features
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* that make lock debugging easier and faster:
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*
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* - uses symbolic names of mutexes, whenever they are printed in debug output
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* - point-of-acquire tracking, symbolic lookup of function names
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* - list of all locks held in the system, printout of them
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* - owner tracking
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* - detects self-recursing locks and prints out all relevant info
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* - detects multi-task circular deadlocks and prints out all affected
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* locks and tasks (and only those tasks)
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*/
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struct mutex {
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/* 1: unlocked, 0: locked, negative: locked, possible waiters */
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struct list_head wait_list;
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atomic_t count;
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};
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/*
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* This is the control structure for tasks blocked on mutex,
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* which resides on the blocked task's kernel stack:
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*/
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struct mutex_waiter {
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struct list_head list;
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int *task;
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};
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#define __MUTEX_INITIALIZER(lockname) \
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{ .wait_list = LIST_HEAD_INIT(lockname.wait_list), \
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.count = ATOMIC_INIT(1) \
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}
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#define DEFINE_MUTEX(mutexname) \
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struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
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void __attribute__ ((fastcall)) __attribute__ ((dllimport))
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mutex_init(struct mutex*)__asm__("MutexInit");
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void __attribute__ ((fastcall)) __attribute__ ((dllimport))
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mutex_lock(struct mutex*)__asm__("MutexLock");
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void __attribute__ ((fastcall)) __attribute__ ((dllimport))
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mutex_unlock(struct mutex*)__asm__("MutexUnlock");
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/**
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* mutex_is_locked - is the mutex locked
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* @lock: the mutex to be queried
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*
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* Returns 1 if the mutex is locked, 0 if unlocked.
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*/
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static inline int mutex_is_locked(struct mutex *lock)
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{
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return atomic_read(&lock->count) != 1;
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}
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#endif
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