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Commit d0945950 authored by Maarten Lankhorst's avatar Maarten Lankhorst Committed by Ingo Molnar
Browse files

lockdep: Check if nested lock is actually held 



It is considered good form to lock the lock you claim to be nested in.

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

[ removed nest_lock arg to print_lock_nested_lock_not_held in favour
  of hlock->nest_lock, also renamed the lock arg to hlock since its
  a held_lock type ]
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/5051A9E7.5040501@canonical.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0bd1189e

kernel/lockdep.c

+39 −0
Original line number Diff line number Diff line
@@ -2998,6 +2998,42 @@ EXPORT_SYMBOL_GPL(lockdep_init_map); 


struct lock_class_key __lockdep_no_validate__;



static int

print_lock_nested_lock_not_held(struct task_struct *curr,

				struct held_lock *hlock,

				unsigned long ip)

{

	if (!debug_locks_off())

		return 0;

	if (debug_locks_silent)

		return 0;



	printk("\n");

	printk("==================================\n");

	printk("[ BUG: Nested lock was not taken ]\n");

	print_kernel_ident();

	printk("----------------------------------\n");



	printk("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));

	print_lock(hlock);



	printk("\nbut this task is not holding:\n");

	printk("%s\n", hlock->nest_lock->name);



	printk("\nstack backtrace:\n");

	dump_stack();



	printk("\nother info that might help us debug this:\n");

	lockdep_print_held_locks(curr);



	printk("\nstack backtrace:\n");

	dump_stack();



	return 0;

}



static int __lock_is_held(struct lockdep_map *lock);



/*

 * This gets called for every mutex_lock*()/spin_lock*() operation.

 * We maintain the dependency maps and validate the locking attempt:
@@ -3139,6 +3175,9 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, 
	}

	chain_key = iterate_chain_key(chain_key, id);



	if (nest_lock && !__lock_is_held(nest_lock))

		return print_lock_nested_lock_not_held(curr, hlock, ip);



	if (!validate_chain(curr, lock, hlock, chain_head, chain_key))

		return 0;