]> git.openfabrics.org - ~shefty/rdma-dev.git/commitdiff
lockdep: Check if nested lock is actually held
authorMaarten Lankhorst <maarten.lankhorst@canonical.com>
Thu, 13 Sep 2012 09:39:51 +0000 (11:39 +0200)
committerIngo Molnar <mingo@kernel.org>
Thu, 13 Sep 2012 15:00:44 +0000 (17:00 +0200)
It is considered good form to lock the lock you claim to be nested in.

Signed-off-by: Maarten 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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/5051A9E7.5040501@canonical.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kernel/lockdep.c

index ea9ee4518c35745a68d917488d387c6d5e09103c..7981e5b2350dd64835608d955d11146c94511170 100644 (file)
@@ -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;