Re: [PATCH 2/7] mutex: add support for reservation style locks

[Maarten Lankhorst <maarten.lankhorst@canonical.com>]

Woops, missed the updated patch description..

Op 15-01-13 13:33, Maarten Lankhorst schreef:
> makes it easier to port ttm over..
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>

mutex_reserve_lock, and mutex_reserve_lock_interruptible:
  Lock a buffer with a reservation_id set. reservation_id must not be set to 0,
  since this is a special value that means no reservation_id.

  Normally if reservation_id is not set, or is older than the reservation_id that's
  currently set on the mutex, the behavior will be to wait normally.

  However, if  the reservation_id is newer than the current reservation_id, -EAGAIN
  will be returned, and this function must unreserve all other mutexes and then redo
  a blocking lock with normal mutex calls to prevent a deadlock, then call
  mutex_locked_set_reservation on successful locking to set the reservation_id inside
  the lock.

  These functions will return -EDEADLK instead of -EAGAIN if reservation_id is the same
  as the reservation_id that's attempted to lock the mutex with, since in that case you
  presumably attempted to lock the same lock twice.

mutex_reserve_lock_slow and mutex_reserve_lock_intr_slow:
  Similar to mutex_reserve_lock, except it won't backoff with -EAGAIN. This is useful
  after mutex_reserve_lock failed with -EAGAIN, and you unreserved all buffers so no
  deadlock can occur.

mutex_unreserve_unlock:
   Unlock a buffer reserved with the previous calls.

Missing at the moment, maybe TODO?
  * lockdep warnings when wrongly calling mutex_unreserve_unlock or mutex_unlock,
    depending on whether reservation_id was set previously or not.
    - Does lockdep have something for this or do I need to extend struct mutex?

  * Check if lockdep warns if you unlock a lock that other locks were nested to.
    - spin_lock(m); spin_lock_nest_lock(a, m); spin_unlock(m); spin_unlock(a);
      would be nice if it gave a splat. Have to recheck if it does, though..

Design:
  I chose for ticket_mutex to encapsulate struct mutex, so the extra memory usage and
  atomic set on init will only happen when you deliberately create a ticket lock.

  Since the mutexes are mostly meant to protect buffer object serialization in ttm, not
  much contention is expected. I could be slightly smarter with wakeups, but this would
  be at the expense at adding a field to struct mutex_waiter. Because this would add
  overhead to all cases where ticket_mutexes are not used, and ticket_mutexes are less
  performance sensitive anyway since they only protect buffer objects, I didn't want to
  do this. It's still better than ttm always calling wake_up_all, which does a
  unconditional spin_lock_irqsave/irqrestore.

  I needed this in kernel/mutex.c because of the extensions to __lock_common, which are
  hopefully optimized away for all normal paths.

Changes since RFC patch v1:
 - Updated to use atomic_long instead of atomic, since the reservation_id was a long.
 - added mutex_reserve_lock_slow and mutex_reserve_lock_intr_slow
 - removed mutex_locked_set_reservation_id (or w/e it was called)

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>

> ---
>  include/linux/mutex.h |  86 +++++++++++++-
>  kernel/mutex.c        | 317 +++++++++++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 387 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 9121595..602c247 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -62,6 +62,11 @@ struct mutex {
>  #endif
>  };
>  
> +struct ticket_mutex {
> +	struct mutex base;
> +	atomic_long_t reservation_id;
> +};
> +
>  /*
>   * This is the control structure for tasks blocked on mutex,
>   * which resides on the blocked task's kernel stack:
> @@ -109,12 +114,24 @@ static inline void mutex_destroy(struct mutex *lock) {}
>  		__DEBUG_MUTEX_INITIALIZER(lockname) \
>  		__DEP_MAP_MUTEX_INITIALIZER(lockname) }
>  
> +#define __TICKET_MUTEX_INITIALIZER(lockname) \
> +		{ .base = __MUTEX_INITIALIZER(lockname) \
> +		, .reservation_id = ATOMIC_LONG_INIT(0) }
> +
>  #define DEFINE_MUTEX(mutexname) \
>  	struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
>  
>  extern void __mutex_init(struct mutex *lock, const char *name,
>  			 struct lock_class_key *key);
>  
> +static inline void __ticket_mutex_init(struct ticket_mutex *lock,
> +				       const char *name,
> +				       struct lock_class_key *key)
> +{
> +	__mutex_init(&lock->base, name, key);
> +	atomic_long_set(&lock->reservation_id, 0);
> +}
> +
>  /**
>   * mutex_is_locked - is the mutex locked
>   * @lock: the mutex to be queried
> @@ -133,26 +150,91 @@ static inline int mutex_is_locked(struct mutex *lock)
>  #ifdef CONFIG_DEBUG_LOCK_ALLOC
>  extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
>  extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
> +
>  extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
>  					unsigned int subclass);
>  extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
>  					unsigned int subclass);
>  
> +extern int __must_check _mutex_reserve_lock(struct ticket_mutex *lock,
> +					struct lockdep_map *nest_lock,
> +					unsigned long reservation_id);
> +
> +extern int __must_check _mutex_reserve_lock_interruptible(struct ticket_mutex *,
> +					struct lockdep_map *nest_lock,
> +					unsigned long reservation_id);
> +
> +extern void _mutex_reserve_lock_slow(struct ticket_mutex *lock,
> +				     struct lockdep_map *nest_lock,
> +				     unsigned long reservation_id);
> +
> +extern int __must_check _mutex_reserve_lock_intr_slow(struct ticket_mutex *,
> +					struct lockdep_map *nest_lock,
> +					unsigned long reservation_id);
> +
>  #define mutex_lock(lock) mutex_lock_nested(lock, 0)
>  #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
>  #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
>  
>  #define mutex_lock_nest_lock(lock, nest_lock)				\
>  do {									\
> -	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);		\
> +	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);	\
>  	_mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);		\
>  } while (0)
>  
> +#define mutex_reserve_lock(lock, nest_lock, reservation_id)		\
> +({									\
> +	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);	\
> +	_mutex_reserve_lock(lock, &(nest_lock)->dep_map, reservation_id);	\
> +})
> +
> +#define mutex_reserve_lock_interruptible(lock, nest_lock, reservation_id)	\
> +({									\
> +	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);	\
> +	_mutex_reserve_lock_interruptible(lock, &(nest_lock)->dep_map,	\
> +					   reservation_id);		\
> +})
> +
> +#define mutex_reserve_lock_slow(lock, nest_lock, reservation_id)	\
> +do {									\
> +	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);	\
> +	_mutex_reserve_lock_slow(lock, &(nest_lock)->dep_map, reservation_id);	\
> +} while (0)
> +
> +#define mutex_reserve_lock_intr_slow(lock, nest_lock, reservation_id)	\
> +({									\
> +	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);	\
> +	_mutex_reserve_lock_intr_slow(lock, &(nest_lock)->dep_map,	\
> +				      reservation_id);			\
> +})
> +
>  #else
>  extern void mutex_lock(struct mutex *lock);
>  extern int __must_check mutex_lock_interruptible(struct mutex *lock);
>  extern int __must_check mutex_lock_killable(struct mutex *lock);
>  
> +extern int __must_check _mutex_reserve_lock(struct ticket_mutex *lock,
> +					    unsigned long reservation_id);
> +extern int __must_check _mutex_reserve_lock_interruptible(struct ticket_mutex *,
> +						unsigned long reservation_id);
> +
> +extern void _mutex_reserve_lock_slow(struct ticket_mutex *lock,
> +				     unsigned long reservation_id);
> +extern int __must_check _mutex_reserve_lock_intr_slow(struct ticket_mutex *,
> +						unsigned long reservation_id);
> +
> +#define mutex_reserve_lock(lock, nest_lock, reservation_id)		\
> +	_mutex_reserve_lock(lock, reservation_id)
> +
> +#define mutex_reserve_lock_interruptible(lock, nest_lock, reservation_id)	\
> +	_mutex_reserve_lock_interruptible(lock, reservation_id)
> +
> +#define mutex_reserve_lock_slow(lock, nest_lock, reservation_id)	\
> +	_mutex_reserve_lock_slow(lock, reservation_id)
> +
> +#define mutex_reserve_lock_intr_slow(lock, nest_lock, reservation_id)	\
> +	_mutex_reserve_lock_intr_slow(lock, reservation_id)
> +
>  # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
>  # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
>  # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
> @@ -167,6 +249,8 @@ extern int __must_check mutex_lock_killable(struct mutex *lock);
>   */
>  extern int mutex_trylock(struct mutex *lock);
>  extern void mutex_unlock(struct mutex *lock);
> +extern void mutex_unreserve_unlock(struct ticket_mutex *lock);
> +
>  extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
>  
>  #ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX
> diff --git a/kernel/mutex.c b/kernel/mutex.c
> index a307cc9..8282729 100644
> --- a/kernel/mutex.c
> +++ b/kernel/mutex.c
> @@ -126,16 +126,119 @@ void __sched mutex_unlock(struct mutex *lock)
>  
>  EXPORT_SYMBOL(mutex_unlock);
>  
> +/**
> + * mutex_unreserve_unlock - release the mutex
> + * @lock: the mutex to be released
> + *
> + * Unlock a mutex that has been locked by this task previously
> + * with _mutex_reserve_lock*.
> + *
> + * This function must not be used in interrupt context. Unlocking
> + * of a not locked mutex is not allowed.
> + */
> +void __sched mutex_unreserve_unlock(struct ticket_mutex *lock)
> +{
> +	/*
> +	 * mark mutex as no longer part of a reservation, next
> +	 * locker can set this again
> +	 */
> +	atomic_long_set(&lock->reservation_id, 0);
> +
> +	/*
> +	 * The unlocking fastpath is the 0->1 transition from 'locked'
> +	 * into 'unlocked' state:
> +	 */
> +#ifndef CONFIG_DEBUG_MUTEXES
> +	/*
> +	 * When debugging is enabled we must not clear the owner before time,
> +	 * the slow path will always be taken, and that clears the owner field
> +	 * after verifying that it was indeed current.
> +	 */
> +	mutex_clear_owner(&lock->base);
> +#endif
> +	__mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath);
> +}
> +EXPORT_SYMBOL(mutex_unreserve_unlock);
> +
> +static inline int __sched
> +__mutex_lock_check_reserve(struct mutex *lock, unsigned long reservation_id)
> +{
> +	struct ticket_mutex *m = container_of(lock, struct ticket_mutex, base);
> +	unsigned long cur_id;
> +
> +	cur_id = atomic_long_read(&m->reservation_id);
> +	if (!cur_id)
> +		return 0;
> +
> +	if (unlikely(reservation_id == cur_id))
> +		return -EDEADLK;
> +
> +	if (unlikely(reservation_id - cur_id <= LONG_MAX))
> +		return -EAGAIN;
> +
> +	return 0;
> +}
> +
> +/*
> + * after acquiring lock with fastpath or when we lost out in contested
> + * slowpath, set reservation_id and wake up any waiters so they can recheck.
> + */
> +static __always_inline void
> +mutex_set_reservation_fastpath(struct ticket_mutex *lock,
> +			       unsigned long reservation_id, bool check_res)
> +{
> +	unsigned long flags;
> +	struct mutex_waiter *cur;
> +
> +	if (check_res || config_enabled(CONFIG_DEBUG_LOCK_ALLOC)) {
> +		unsigned long cur_id;
> +
> +		cur_id = atomic_long_xchg(&lock->reservation_id,
> +					  reservation_id);
> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> +		if (check_res)
> +			DEBUG_LOCKS_WARN_ON(cur_id &&
> +					   cur_id != reservation_id);
> +		else
> +			DEBUG_LOCKS_WARN_ON(cur_id);
> +		lockdep_assert_held(&lock->base);
> +#endif
> +
> +		if (unlikely(cur_id == reservation_id))
> +			return;
> +	} else
> +		atomic_long_set(&lock->reservation_id, reservation_id);
> +
> +	/*
> +	 * Check if lock is contended, if not there is nobody to wake up
> +	 */
> +	if (likely(atomic_read(&lock->base.count) == 0))
> +		return;
> +
> +	/*
> +	 * Uh oh, we raced in fastpath, wake up everyone in this case,
> +	 * so they can see the new reservation_id
> +	 */
> +	spin_lock_mutex(&lock->base.wait_lock, flags);
> +	list_for_each_entry(cur, &lock->base.wait_list, list) {
> +		debug_mutex_wake_waiter(&lock->base, cur);
> +		wake_up_process(cur->task);
> +	}
> +	spin_unlock_mutex(&lock->base.wait_lock, flags);
> +}
> +
>  /*
>   * Lock a mutex (possibly interruptible), slowpath:
>   */
>  static inline int __sched
>  __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
> -		    struct lockdep_map *nest_lock, unsigned long ip)
> +		    struct lockdep_map *nest_lock, unsigned long ip,
> +		    unsigned long reservation_id, bool res_slow)
>  {
>  	struct task_struct *task = current;
>  	struct mutex_waiter waiter;
>  	unsigned long flags;
> +	int ret;
>  
>  	preempt_disable();
>  	mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
> @@ -162,6 +265,12 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
>  	for (;;) {
>  		struct task_struct *owner;
>  
> +		if (!__builtin_constant_p(reservation_id) && !res_slow) {
> +			ret = __mutex_lock_check_reserve(lock, reservation_id);
> +			if (ret)
> +				goto err_nowait;
> +		}
> +
>  		/*
>  		 * If there's an owner, wait for it to either
>  		 * release the lock or go to sleep.
> @@ -172,6 +281,13 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
>  
>  		if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {
>  			lock_acquired(&lock->dep_map, ip);
> +			if (res_slow) {
> +				struct ticket_mutex *m;
> +				m = container_of(lock, struct ticket_mutex, base);
> +
> +				mutex_set_reservation_fastpath(m, reservation_id, false);
> +			}
> +
>  			mutex_set_owner(lock);
>  			preempt_enable();
>  			return 0;
> @@ -227,15 +343,16 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
>  		 * TASK_UNINTERRUPTIBLE case.)
>  		 */
>  		if (unlikely(signal_pending_state(state, task))) {
> -			mutex_remove_waiter(lock, &waiter,
> -					    task_thread_info(task));
> -			mutex_release(&lock->dep_map, 1, ip);
> -			spin_unlock_mutex(&lock->wait_lock, flags);
> +			ret = -EINTR;
> +			goto err;
> +		}
>  
> -			debug_mutex_free_waiter(&waiter);
> -			preempt_enable();
> -			return -EINTR;
> +		if (!__builtin_constant_p(reservation_id) && !res_slow) {
> +			ret = __mutex_lock_check_reserve(lock, reservation_id);
> +			if (ret)
> +				goto err;
>  		}
> +
>  		__set_task_state(task, state);
>  
>  		/* didn't get the lock, go to sleep: */
> @@ -250,6 +367,28 @@ done:
>  	mutex_remove_waiter(lock, &waiter, current_thread_info());
>  	mutex_set_owner(lock);
>  
> +	if (!__builtin_constant_p(reservation_id)) {
> +		struct ticket_mutex *m;
> +		struct mutex_waiter *cur;
> +		/*
> +		 * this should get optimized out for the common case,
> +		 * and is only important for _mutex_reserve_lock
> +		 */
> +
> +		m = container_of(lock, struct ticket_mutex, base);
> +		atomic_long_set(&m->reservation_id, reservation_id);
> +
> +		/*
> +		 * give any possible sleeping processes the chance to wake up,
> +		 * so they can recheck if they have to back off from
> +		 * reservations
> +		 */
> +		list_for_each_entry(cur, &lock->wait_list, list) {
> +			debug_mutex_wake_waiter(lock, cur);
> +			wake_up_process(cur->task);
> +		}
> +	}
> +
>  	/* set it to 0 if there are no waiters left: */
>  	if (likely(list_empty(&lock->wait_list)))
>  		atomic_set(&lock->count, 0);
> @@ -260,6 +399,19 @@ done:
>  	preempt_enable();
>  
>  	return 0;
> +
> +err:
> +	mutex_remove_waiter(lock, &waiter, task_thread_info(task));
> +	spin_unlock_mutex(&lock->wait_lock, flags);
> +	debug_mutex_free_waiter(&waiter);
> +
> +#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
> +err_nowait:
> +#endif
> +	mutex_release(&lock->dep_map, 1, ip);
> +
> +	preempt_enable();
> +	return ret;
>  }
>  
>  #ifdef CONFIG_DEBUG_LOCK_ALLOC
> @@ -267,7 +419,8 @@ void __sched
>  mutex_lock_nested(struct mutex *lock, unsigned int subclass)
>  {
>  	might_sleep();
> -	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
> +	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
> +			    subclass, NULL, _RET_IP_, 0, 0);
>  }
>  
>  EXPORT_SYMBOL_GPL(mutex_lock_nested);
> @@ -276,7 +429,8 @@ void __sched
>  _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
>  {
>  	might_sleep();
> -	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_);
> +	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
> +			    0, nest, _RET_IP_, 0, 0);
>  }
>  
>  EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
> @@ -285,7 +439,8 @@ int __sched
>  mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
>  {
>  	might_sleep();
> -	return __mutex_lock_common(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_);
> +	return __mutex_lock_common(lock, TASK_KILLABLE,
> +				   subclass, NULL, _RET_IP_, 0, 0);
>  }
>  EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
>  
> @@ -294,10 +449,63 @@ mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
>  {
>  	might_sleep();
>  	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
> -				   subclass, NULL, _RET_IP_);
> +				   subclass, NULL, _RET_IP_, 0, 0);
>  }
>  
>  EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
> +
> +int __sched
> +_mutex_reserve_lock(struct ticket_mutex *lock, struct lockdep_map *nest,
> +		    unsigned long reservation_id)
> +{
> +	DEBUG_LOCKS_WARN_ON(!reservation_id);
> +
> +	might_sleep();
> +	return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
> +				   0, nest, _RET_IP_, reservation_id, 0);
> +}
> +EXPORT_SYMBOL_GPL(_mutex_reserve_lock);
> +
> +
> +int __sched
> +_mutex_reserve_lock_interruptible(struct ticket_mutex *lock,
> +				  struct lockdep_map *nest,
> +				  unsigned long reservation_id)
> +{
> +	DEBUG_LOCKS_WARN_ON(!reservation_id);
> +
> +	might_sleep();
> +	return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
> +				   0, nest, _RET_IP_, reservation_id, 0);
> +}
> +EXPORT_SYMBOL_GPL(_mutex_reserve_lock_interruptible);
> +
> +void __sched
> +_mutex_reserve_lock_slow(struct ticket_mutex *lock, struct lockdep_map *nest,
> +			 unsigned long reservation_id)
> +{
> +	DEBUG_LOCKS_WARN_ON(!reservation_id);
> +
> +	might_sleep();
> +	__mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
> +			    nest, _RET_IP_, reservation_id, 1);
> +}
> +EXPORT_SYMBOL_GPL(_mutex_reserve_lock_slow);
> +
> +int __sched
> +_mutex_reserve_lock_intr_slow(struct ticket_mutex *lock,
> +			      struct lockdep_map *nest,
> +			      unsigned long reservation_id)
> +{
> +	DEBUG_LOCKS_WARN_ON(!reservation_id);
> +
> +	might_sleep();
> +	return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
> +				   nest, _RET_IP_, reservation_id, 1);
> +}
> +EXPORT_SYMBOL_GPL(_mutex_reserve_lock_intr_slow);
> +
> +
>  #endif
>  
>  /*
> @@ -400,7 +608,8 @@ __mutex_lock_slowpath(atomic_t *lock_count)
>  {
>  	struct mutex *lock = container_of(lock_count, struct mutex, count);
>  
> -	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
> +	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
> +			    NULL, _RET_IP_, 0, 0);
>  }
>  
>  static noinline int __sched
> @@ -408,7 +617,8 @@ __mutex_lock_killable_slowpath(atomic_t *lock_count)
>  {
>  	struct mutex *lock = container_of(lock_count, struct mutex, count);
>  
> -	return __mutex_lock_common(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
> +	return __mutex_lock_common(lock, TASK_KILLABLE, 0,
> +				   NULL, _RET_IP_, 0, 0);
>  }
>  
>  static noinline int __sched
> @@ -416,8 +626,28 @@ __mutex_lock_interruptible_slowpath(atomic_t *lock_count)
>  {
>  	struct mutex *lock = container_of(lock_count, struct mutex, count);
>  
> -	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
> +	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
> +				   NULL, _RET_IP_, 0, 0);
> +}
> +
> +static noinline int __sched
> +__mutex_lock_reserve_slowpath(atomic_t *lock_count, void *rid)
> +{
> +	struct mutex *lock = container_of(lock_count, struct mutex, count);
> +
> +	return __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
> +				   NULL, _RET_IP_, (unsigned long)rid, 0);
> +}
> +
> +static noinline int __sched
> +__mutex_lock_interruptible_reserve_slowpath(atomic_t *lock_count, void *rid)
> +{
> +	struct mutex *lock = container_of(lock_count, struct mutex, count);
> +
> +	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
> +				   NULL, _RET_IP_, (unsigned long)rid, 0);
>  }
> +
>  #endif
>  
>  /*
> @@ -473,6 +703,63 @@ int __sched mutex_trylock(struct mutex *lock)
>  }
>  EXPORT_SYMBOL(mutex_trylock);
>  
> +#ifndef CONFIG_DEBUG_LOCK_ALLOC
> +int __sched
> +_mutex_reserve_lock(struct ticket_mutex *lock, unsigned long rid)
> +{
> +	int ret;
> +
> +	might_sleep();
> +
> +	ret = __mutex_fastpath_lock_retval_arg(&lock->base.count, (void *)rid,
> +					__mutex_lock_reserve_slowpath);
> +
> +	if (!ret) {
> +		mutex_set_reservation_fastpath(lock, rid, true);
> +		mutex_set_owner(&lock->base);
> +	}
> +	return ret;
> +}
> +EXPORT_SYMBOL(_mutex_reserve_lock);
> +
> +int __sched
> +_mutex_reserve_lock_interruptible(struct ticket_mutex *lock, unsigned long rid)
> +{
> +	int ret;
> +
> +	might_sleep();
> +
> +	ret = __mutex_fastpath_lock_retval_arg(&lock->base.count, (void *)rid,
> +				__mutex_lock_interruptible_reserve_slowpath);
> +
> +	if (!ret) {
> +		mutex_set_reservation_fastpath(lock, rid, true);
> +		mutex_set_owner(&lock->base);
> +	}
> +	return ret;
> +}
> +EXPORT_SYMBOL(_mutex_reserve_lock_interruptible);
> +
> +void __sched
> +_mutex_reserve_lock_slow(struct ticket_mutex *lock, unsigned long rid)
> +{
> +	might_sleep();
> +	__mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
> +			    0, NULL, _RET_IP_, rid, 1);
> +}
> +EXPORT_SYMBOL(_mutex_reserve_lock_slow);
> +
> +int __sched
> +_mutex_reserve_lock_intr_slow(struct ticket_mutex *lock, unsigned long rid)
> +{
> +	might_sleep();
> +	return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
> +				   0, NULL, _RET_IP_, rid, 1);
> +}
> +EXPORT_SYMBOL(_mutex_reserve_lock_intr_slow);
> +
> +#endif
> +
>  /**
>   * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
>   * @cnt: the atomic which we are to dec