linux/include/linux/mutex_types.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_MUTEX_TYPES_H
#define __LINUX_MUTEX_TYPES_H

#include <linux/atomic.h>
#include <linux/lockdep_types.h>
#include <linux/osq_lock.h>
#include <linux/spinlock_types.h>
#include <linux/types.h>

#ifndef CONFIG_PREEMPT_RT

/*
 * 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 { … };

#else /* !CONFIG_PREEMPT_RT */
/*
 * Preempt-RT variant based on rtmutexes.
 */
#include <linux/rtmutex.h>

struct mutex {
	struct rt_mutex_base	rtmutex;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map	dep_map;
#endif
};

#endif /* CONFIG_PREEMPT_RT */

#endif /* __LINUX_MUTEX_TYPES_H */