From: Steven Rostedt The lockdep output can be pretty cryptic, having a nice output can save a lot of head scratching. When a simple deadlock scenario is detected by lockdep (lock A -> lock A) we get the following output: other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(lock)->rlock); lock(&(lock)->rlock); *** DEADLOCK *** Acked-by: Peter Zijlstra Signed-off-by: Steven Rostedt --- kernel/lockdep.c | 21 +++++++++++++++++++++ 1 files changed, 21 insertions(+), 0 deletions(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 1039008..a0f253b 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -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"); -- 1.7.2.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/