Messages in this thread Patch in this message | | | Date | Wed, 20 Apr 2011 21:41:56 -0400 | From | Steven Rostedt <> | Subject | [PATCH 3/7] lockdep: Print a nice description of simple deadlock |
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From: Steven Rostedt <srostedt@redhat.com>
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 <a.p.zijlstra@chello.nl> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- 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
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