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  * @tree_entry:		pi node to enqueue into the mutex waiters tree
44  * @pi_tree_entry:	pi node to enqueue into the mutex owner waiters tree
45  * @task:		task reference to the blocked task
46  */
47 struct rt_mutex_waiter {
48 	struct rb_node          tree_entry;
49 	struct rb_node          pi_tree_entry;
50 	struct task_struct	*task;
51 	struct rt_mutex		*lock;
52 #ifdef CONFIG_DEBUG_RT_MUTEXES
53 	unsigned long		ip;
54 	struct pid		*deadlock_task_pid;
55 	struct rt_mutex		*deadlock_lock;
56 #endif
57 	int prio;
58 };
59 
60 /*
61  * Various helpers to access the waiters-tree:
62  */
63 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
64 {
65 	return !RB_EMPTY_ROOT(&lock->waiters);
66 }
67 
68 static inline struct rt_mutex_waiter *
69 rt_mutex_top_waiter(struct rt_mutex *lock)
70 {
71 	struct rt_mutex_waiter *w;
72 
73 	w = rb_entry(lock->waiters_leftmost, struct rt_mutex_waiter,
74 		     tree_entry);
75 	BUG_ON(w->lock != lock);
76 
77 	return w;
78 }
79 
80 static inline int task_has_pi_waiters(struct task_struct *p)
81 {
82 	return !RB_EMPTY_ROOT(&p->pi_waiters);
83 }
84 
85 static inline struct rt_mutex_waiter *
86 task_top_pi_waiter(struct task_struct *p)
87 {
88 	return rb_entry(p->pi_waiters_leftmost, struct rt_mutex_waiter,
89 			pi_tree_entry);
90 }
91 
92 /*
93  * lock->owner state tracking:
94  */
95 #define RT_MUTEX_HAS_WAITERS	1UL
96 #define RT_MUTEX_OWNER_MASKALL	1UL
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 /*
105  * Constants for rt mutex functions which have a selectable deadlock
106  * detection.
107  *
108  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
109  *				no further PI adjustments to be made.
110  *
111  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
112  *				walk of the lock chain.
113  */
114 enum rtmutex_chainwalk {
115 	RT_MUTEX_MIN_CHAINWALK,
116 	RT_MUTEX_FULL_CHAINWALK,
117 };
118 
119 /*
120  * PI-futex support (proxy locking functions, etc.):
121  */
122 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
123 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
124 				       struct task_struct *proxy_owner);
125 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
126 				  struct task_struct *proxy_owner);
127 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
128 				     struct rt_mutex_waiter *waiter,
129 				     struct task_struct *task);
130 extern int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
131 				      struct hrtimer_sleeper *to,
132 				      struct rt_mutex_waiter *waiter);
133 extern int rt_mutex_timed_futex_lock(struct rt_mutex *l, struct hrtimer_sleeper *to);
134 
135 #ifdef CONFIG_DEBUG_RT_MUTEXES
136 # include "rtmutex-debug.h"
137 #else
138 # include "rtmutex.h"
139 #endif
140 
141 #endif
142