Commit 282b5c2f authored Apr 20, 2011 by Steven Rostedt Committed by Ingo Molnar Apr 22, 2011

lockdep: Print a nicer description for simple irq lock inversions



Lockdep output can be pretty cryptic, having nicer output
can save a lot of head scratching. When a simple irq inversion
scenario is detected by lockdep (lock A taken in interrupt
context but also in thread context without disabling interrupts)
we now get the following (hopefully more informative) output:

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

       CPU0
       ----
  lock(lockA);
  <Interrupt>
    lock(lockA);

 *** DEADLOCK ***

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Peter 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/20110421014300.436140880@goodmis.org


Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 6be8c393

kernel/lockdep.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -2158,6 +2158,24 @@ static void check_chain_key(struct task_struct *curr)
		#endif
		}

		static void
		print_usage_bug_scenario(struct held_lock *lock)
		{
		struct lock_class *class = hlock_class(lock);

		printk(" Possible unsafe locking scenario:\n\n");
		printk(" CPU0\n");
		printk(" ----\n");
		printk(" lock(");
		__print_lock_name(class);
		printk(");\n");
		printk(" <Interrupt>\n");
		printk(" lock(");
		__print_lock_name(class);
		printk(");\n");
		printk("\n * DEADLOCK *\n\n");
		}

		static int
		print_usage_bug(struct task_struct curr, struct held_lock this,
		enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
		@@ -2186,6 +2204,8 @@ print_usage_bug(struct task_struct curr, struct held_lock this,

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

		lockdep_print_held_locks(curr);

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

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