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Commit 6419c4af authored by J. R. Okajima's avatar J. R. Okajima Committed by Ingo Molnar
Browse files

locking/lockdep: Add new check to lock_downgrade() 

Commit:

  f8319483 ("locking/lockdep: Provide a type check for lock_is_held")

didn't fully cover rwsems as downgrade_write() was left out.

Introduce lock_downgrade() and use it to add new checks.

See-also: http://marc.info/?l=linux-kernel&m=148581164003149&w=2


Originally-written-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarJ. R. Okajima <hooanon05g@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1486053497-9948-3-git-send-email-hooanon05g@gmail.com


[ Rewrote the changelog. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent e969970b

include/linux/lockdep.h

+3 −0
Original line number Diff line number Diff line
@@ -361,6 +361,8 @@ static inline void lock_set_subclass(struct lockdep_map *lock, 
	lock_set_class(lock, lock->name, lock->key, subclass, ip);

}



extern void lock_downgrade(struct lockdep_map *lock, unsigned long ip);



extern void lockdep_set_current_reclaim_state(gfp_t gfp_mask);

extern void lockdep_clear_current_reclaim_state(void);

extern void lockdep_trace_alloc(gfp_t mask);
@@ -411,6 +413,7 @@ static inline void lockdep_on(void) 


# define lock_acquire(l, s, t, r, c, n, i)	do { } while (0)

# define lock_release(l, n, i)			do { } while (0)

# define lock_downgrade(l, i)			do { } while (0)

# define lock_set_class(l, n, k, s, i)		do { } while (0)

# define lock_set_subclass(l, s, i)		do { } while (0)

# define lockdep_set_current_reclaim_state(g)	do { } while (0)

kernel/locking/lockdep.c

+55 −0
Original line number Diff line number Diff line
@@ -3533,6 +3533,44 @@ __lock_set_class(struct lockdep_map *lock, const char *name, 
	return 1;

}



static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)

{

	struct task_struct *curr = current;

	struct held_lock *hlock;

	unsigned int depth;

	int i;



	depth = curr->lockdep_depth;

	/*

	 * This function is about (re)setting the class of a held lock,

	 * yet we're not actually holding any locks. Naughty user!

	 */

	if (DEBUG_LOCKS_WARN_ON(!depth))

		return 0;



	hlock = find_held_lock(curr, lock, depth, &i);

	if (!hlock)

		return print_unlock_imbalance_bug(curr, lock, ip);



	curr->lockdep_depth = i;

	curr->curr_chain_key = hlock->prev_chain_key;



	WARN(hlock->read, "downgrading a read lock");

	hlock->read = 1;

	hlock->acquire_ip = ip;



	if (reacquire_held_locks(curr, depth, i))

		return 0;



	/*

	 * I took it apart and put it back together again, except now I have

	 * these 'spare' parts.. where shall I put them.

	 */

	if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))

		return 0;

	return 1;

}



/*

 * Remove the lock to the list of currently held locks - this gets

 * called on mutex_unlock()/spin_unlock*() (or on a failed
@@ -3759,6 +3797,23 @@ void lock_set_class(struct lockdep_map *lock, const char *name, 
}

EXPORT_SYMBOL_GPL(lock_set_class);



void lock_downgrade(struct lockdep_map *lock, unsigned long ip)

{

	unsigned long flags;



	if (unlikely(current->lockdep_recursion))

		return;



	raw_local_irq_save(flags);

	current->lockdep_recursion = 1;

	check_flags(flags);

	if (__lock_downgrade(lock, ip))

		check_chain_key(current);

	current->lockdep_recursion = 0;

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_downgrade);



/*

 * We are not always called with irqs disabled - do that here,

 * and also avoid lockdep recursion:

kernel/locking/rwsem.c

+2 −4
Original line number Diff line number Diff line
@@ -124,10 +124,8 @@ EXPORT_SYMBOL(up_write); 
 */

void downgrade_write(struct rw_semaphore *sem)

{

	/*

	 * lockdep: a downgraded write will live on as a write

	 * dependency.

	 */

	lock_downgrade(&sem->dep_map, _RET_IP_);



	rwsem_set_reader_owned(sem);

	__downgrade_write(sem);

}