kernel/rtmutex_common.h

   1 /*
   2  * RT Mutexes: blocking mutual exclusion locks with PI support
   3  *
   4  * started by Ingo Molnar and Thomas Gleixner:
   5  *
   6  *  Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   7  *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
   8  *
   9  * This file contains the private data structure and API definitions.
  10  */
  11
  12 #ifndef __KERNEL_RTMUTEX_COMMON_H
  13 #define __KERNEL_RTMUTEX_COMMON_H
  14
  15 #include <linux/rtmutex.h>
  16
  17 /*
  18  * The rtmutex in kernel tester is independent of rtmutex debugging. We
  19  * call schedule_rt_mutex_test() instead of schedule() for the tasks which
  20  * belong to the tester. That way we can delay the wakeup path of those
  21  * threads to provoke lock stealing and testing of  complex boosting scenarios.
  22  */
  23 #ifdef CONFIG_RT_MUTEX_TESTER
  24
  25 extern void schedule_rt_mutex_test(struct rt_mutex *lock);
  26
  27 #define schedule_rt_mutex(_lock)                                \
  28   do {                                                          \
  29         if (!(current->flags & PF_MUTEX_TESTER))                \
  30                 schedule();                                     \
  31         else                                                    \
  32                 schedule_rt_mutex_test(_lock);                  \
  33   } while (0)
  34
  35 #else
  36 # define schedule_rt_mutex(_lock)                       schedule()
  37 #endif
  38
  39 /*
  40  * This is the control structure for tasks blocked on a rt_mutex,
  41  * which is allocated on the kernel stack on of the blocked task.
  42  *
  43  * @list_entry:         pi node to enqueue into the mutex waiters list
  44  * @pi_list_entry:      pi node to enqueue into the mutex owner waiters list
  45  * @task:               task reference to the blocked task
  46  */
  47 struct rt_mutex_waiter {
  48         struct plist_node       list_entry;
  49         struct plist_node       pi_list_entry;
  50         struct task_struct      *task;
  51         struct rt_mutex         *lock;
  52 #ifdef CONFIG_DEBUG_RT_MUTEXES
  53         unsigned long           ip;
  54         pid_t                   deadlock_task_pid;
  55         struct rt_mutex         *deadlock_lock;
  56 #endif
  57 };
  58
  59 /*
  60  * Various helpers to access the waiters-plist:
  61  */
  62 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
  63 {
  64         return !plist_head_empty(&lock->wait_list);
  65 }
  66
  67 static inline struct rt_mutex_waiter *
  68 rt_mutex_top_waiter(struct rt_mutex *lock)
  69 {
  70         struct rt_mutex_waiter *w;
  71
  72         w = plist_first_entry(&lock->wait_list, struct rt_mutex_waiter,
  73                                list_entry);
  74         BUG_ON(w->lock != lock);
  75
  76         return w;
  77 }
  78
  79 static inline int task_has_pi_waiters(struct task_struct *p)
  80 {
  81         return !plist_head_empty(&p->pi_waiters);
  82 }
  83
  84 static inline struct rt_mutex_waiter *
  85 task_top_pi_waiter(struct task_struct *p)
  86 {
  87         return plist_first_entry(&p->pi_waiters, struct rt_mutex_waiter,
  88                                   pi_list_entry);
  89 }
  90
  91 /*
  92  * lock->owner state tracking:
  93  */
  94 #define RT_MUTEX_OWNER_PENDING  1UL
  95 #define RT_MUTEX_HAS_WAITERS    2UL
  96 #define RT_MUTEX_OWNER_MASKALL  3UL
  97
  98 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
  99 {
 100         return (struct task_struct *)
 101                 ((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL);
 102 }
 103
 104 static inline struct task_struct *rt_mutex_real_owner(struct rt_mutex *lock)
 105 {
 106         return (struct task_struct *)
 107                 ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
 108 }
 109
 110 static inline unsigned long rt_mutex_owner_pending(struct rt_mutex *lock)
 111 {
 112         return (unsigned long)lock->owner & RT_MUTEX_OWNER_PENDING;
 113 }
 114
 115 /*
 116  * We can speed up the acquire/release, if the architecture
 117  * supports cmpxchg and if there's no debugging state to be set up
 118  */
 119 #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
 120 # define rt_mutex_cmpxchg(l,c,n)        (cmpxchg(&l->owner, c, n) == c)
 121 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
 122 {
 123         unsigned long owner, *p = (unsigned long *) &lock->owner;
 124
 125         do {
 126                 owner = *p;
 127         } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
 128 }
 129 #else
 130 # define rt_mutex_cmpxchg(l,c,n)        (0)
 131 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
 132 {
 133         lock->owner = (struct task_struct *)
 134                         ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
 135 }
 136 #endif
 137
 138 /*
 139  * PI-futex support (proxy locking functions, etc.):
 140  */
 141 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
 142 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
 143                                        struct task_struct *proxy_owner);
 144 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
 145                                   struct task_struct *proxy_owner);
 146
 147 extern void rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
 148                                unsigned long mask);
 149 extern void __rt_mutex_adjust_prio(struct task_struct *task);
 150 extern int rt_mutex_adjust_prio_chain(struct task_struct *task,
 151                                       int deadlock_detect,
 152                                       struct rt_mutex *orig_lock,
 153                                       struct rt_mutex_waiter *orig_waiter,
 154                                       struct task_struct *top_task);
 155 extern void remove_waiter(struct rt_mutex *lock,
 156                           struct rt_mutex_waiter *waiter);
 157 #endif