include/linux/mutex_types.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_MUTEX_TYPES_H
   3 #define __LINUX_MUTEX_TYPES_H
   4
   5 #include <linux/atomic.h>
   6 #include <linux/lockdep_types.h>
   7 #include <linux/osq_lock.h>
   8 #include <linux/spinlock_types.h>
   9 #include <linux/types.h>
  10
  11 #ifndef CONFIG_PREEMPT_RT
  12
  13 /*
  14  * Simple, straightforward mutexes with strict semantics:
  15  *
  16  * - only one task can hold the mutex at a time
  17  * - only the owner can unlock the mutex
  18  * - multiple unlocks are not permitted
  19  * - recursive locking is not permitted
  20  * - a mutex object must be initialized via the API
  21  * - a mutex object must not be initialized via memset or copying
  22  * - task may not exit with mutex held
  23  * - memory areas where held locks reside must not be freed
  24  * - held mutexes must not be reinitialized
  25  * - mutexes may not be used in hardware or software interrupt
  26  *   contexts such as tasklets and timers
  27  *
  28  * These semantics are fully enforced when DEBUG_MUTEXES is
  29  * enabled. Furthermore, besides enforcing the above rules, the mutex
  30  * debugging code also implements a number of additional features
  31  * that make lock debugging easier and faster:
  32  *
  33  * - uses symbolic names of mutexes, whenever they are printed in debug output
  34  * - point-of-acquire tracking, symbolic lookup of function names
  35  * - list of all locks held in the system, printout of them
  36  * - owner tracking
  37  * - detects self-recursing locks and prints out all relevant info
  38  * - detects multi-task circular deadlocks and prints out all affected
  39  *   locks and tasks (and only those tasks)
  40  */
  41 struct mutex {
  42         atomic_long_t           owner;
  43         raw_spinlock_t          wait_lock;
  44 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
  45         struct optimistic_spin_queue osq; /* Spinner MCS lock */
  46 #endif
  47         struct list_head        wait_list;
  48 #ifdef CONFIG_DEBUG_MUTEXES
  49         void                    *magic;
  50 #endif
  51 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  52         struct lockdep_map      dep_map;
  53 #endif
  54 };
  55
  56 #else /* !CONFIG_PREEMPT_RT */
  57 /*
  58  * Preempt-RT variant based on rtmutexes.
  59  */
  60 #include <linux/rtmutex.h>
  61
  62 struct mutex {
  63         struct rt_mutex_base    rtmutex;
  64 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  65         struct lockdep_map      dep_map;
  66 #endif
  67 };
  68
  69 #endif /* CONFIG_PREEMPT_RT */
  70
  71 #endif /* __LINUX_MUTEX_TYPES_H */