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/*

 * Simple, straightforward mutexes with strict semantics: * * - only one task can hold the mutex at a time * - only the owner can unlock the mutex * - multiple unlocks are not permitted * - recursive locking is not permitted * - a mutex object must be initialized via the API * - a mutex object must not be initialized via memset or copying * - task may not exit with mutex held * - memory areas where held locks reside must not be freed * - held mutexes must not be reinitialized * - mutexes may not be used in hardware or software interrupt *   contexts such as tasklets and timers * * These semantics are fully enforced when DEBUG_MUTEXES is * enabled. Furthermore, besides enforcing the above rules, the mutex * debugging code also implements a number of additional features * that make lock debugging easier and faster: * * - uses symbolic names of mutexes, whenever they are printed in debug output * - point-of-acquire tracking, symbolic lookup of function names * - list of all locks held in the system, printout of them * - owner tracking * - detects self-recursing locks and prints out all relevant info * - detects multi-task circular deadlocks and prints out all affected *   locks and tasks (and only those tasks) */struct mutex {	/* 1: unlocked, 0: locked, negative: locked, possible waiters */	atomic_t		count;	spinlock_t		wait_lock;	struct list_head	wait_list;#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_MUTEX_SPIN_ON_OWNER)	struct task_struct	*owner;#endif#ifdef CONFIG_MUTEX_SPIN_ON_OWNER	struct optimistic_spin_queue osq; /* Spinner MCS lock */#endif#ifdef CONFIG_DEBUG_MUTEXES	void			*magic;#endif#ifdef CONFIG_DEBUG_LOCK_ALLOC	struct lockdep_map	dep_map;#endif};

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