rtmutex_common.h

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/*
 * RT Mutexes: blocking mutual exclusion locks with PI support
 *
 * started by Ingo Molnar and Thomas Gleixner:
 *
 *  Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <[email protected]>
 *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <[email protected]>
 *
 * This file contains the private data structure and API definitions.
 */

#ifndef __KERNEL_RTMUTEX_COMMON_H
#define __KERNEL_RTMUTEX_COMMON_H

#include <linux/rtmutex.h>

/*
 * The rtmutex in kernel tester is independent of rtmutex debugging. We
 * call schedule_rt_mutex_test() instead of schedule() for the tasks which
 * belong to the tester. That way we can delay the wakeup path of those
 * threads to provoke lock stealing and testing of  complex boosting scenarios.
 */
#ifdef CONFIG_RT_MUTEX_TESTER

extern void schedule_rt_mutex_test(struct rt_mutex *lock);

#define schedule_rt_mutex(_lock)                \
  do {                              \
    if (!(current->flags & PF_MUTEX_TESTER))        \
        schedule();                 \
    else                            \
        schedule_rt_mutex_test(_lock);          \
  } while (0)

#else
# define schedule_rt_mutex(_lock)           schedule()
#endif

/*
 * This is the control structure for tasks blocked on a rt_mutex,
 * which is allocated on the kernel stack on of the blocked task.
 *
 * @list_entry:     pi node to enqueue into the mutex waiters list
 * @pi_list_entry:  pi node to enqueue into the mutex owner waiters list
 * @task:       task reference to the blocked task
 */
struct rt_mutex_waiter {
    struct plist_node   list_entry;
    struct plist_node   pi_list_entry;
    struct task_struct  *task;
    struct rt_mutex     *lock;
#ifdef CONFIG_DEBUG_RT_MUTEXES
    unsigned long       ip;
    struct pid      *deadlock_task_pid;
    struct rt_mutex     *deadlock_lock;
#endif
};

/*
 * Various helpers to access the waiters-plist:
 */
static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
{
    return !plist_head_empty(&lock->wait_list);
}

static inline struct rt_mutex_waiter *
rt_mutex_top_waiter(struct rt_mutex *lock)
{
    struct rt_mutex_waiter *w;

    w = plist_first_entry(&lock->wait_list, struct rt_mutex_waiter,
                   list_entry);
    BUG_ON(w->lock != lock);

    return w;
}

static inline int task_has_pi_waiters(struct task_struct *p)
{
    return !plist_head_empty(&p->pi_waiters);
}

static inline struct rt_mutex_waiter *
task_top_pi_waiter(struct task_struct *p)
{
    return plist_first_entry(&p->pi_waiters, struct rt_mutex_waiter,
                  pi_list_entry);
}

/*
 * lock->owner state tracking:
 */
#define RT_MUTEX_HAS_WAITERS    1UL
#define RT_MUTEX_OWNER_MASKALL  1UL

static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
{
    return (struct task_struct *)
        ((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL);
}

/*
 * PI-futex support (proxy locking functions, etc.):
 */
extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
                       struct task_struct *proxy_owner);
extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
                  struct task_struct *proxy_owner);
extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
                     struct rt_mutex_waiter *waiter,
                     struct task_struct *task,
                     int detect_deadlock);
extern int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
                      struct hrtimer_sleeper *to,
                      struct rt_mutex_waiter *waiter,
                      int detect_deadlock);

#ifdef CONFIG_DEBUG_RT_MUTEXES
# include "rtmutex-debug.h"
#else
# include "rtmutex.h"
#endif

#endif