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Commit 48702ecf authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
Browse files

lockdep: Print a nicer description for simple deadlocks 



Lockdep output can be pretty cryptic, having nicer output
can save a lot of head scratching. When a simple deadlock
scenario is detected by lockdep (lock A -> lock A) we now
get the following new output:

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&(lock)->rlock);
  lock(&(lock)->rlock);

 *** DEADLOCK ***

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20110421014259.643930104@goodmis.org


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f4185812

kernel/lockdep.c

+21 −0
Original line number Diff line number Diff line
@@ -1664,6 +1664,26 @@ static inline void inc_chains(void) 


#endif



static void

print_deadlock_scenario(struct held_lock *nxt,

			     struct held_lock *prv)

{

	struct lock_class *next = hlock_class(nxt);

	struct lock_class *prev = hlock_class(prv);



	printk(" Possible unsafe locking scenario:\n\n");

	printk("       CPU0\n");

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

	printk("  lock(");

	__print_lock_name(prev);

	printk(");\n");

	printk("  lock(");

	__print_lock_name(next);

	printk(");\n");

	printk("\n *** DEADLOCK ***\n\n");

	printk(" May be due to missing lock nesting notation\n\n");

}



static int

print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,

		   struct held_lock *next)
@@ -1682,6 +1702,7 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, 
	print_lock(prev);



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

	print_deadlock_scenario(next, prev);

	lockdep_print_held_locks(curr);



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