Re: [PATCH 0/2] Debug bits for the tty ldisc problem

[Ingo Molnar]

* Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote:

> On Mon, 15 Jun 2009 16:39:56 +0200
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> > On Mon, 2009-06-15 at 16:32 +0100, Alan Cox wrote:
> > > I'm not 100% sure the close one is
> > > safe for locking but as the lock detector has been busted since 2.6.30 its a
> > > bit hard to be sure.
> > 
> > Would you have some specifics?
> 
> I stuck it in bugzilla basically it blows up with a 
> 
> BUG: MAX_STACK_TRACE_ENTRIES too low! turning off the locking 
> correctness validator.
> 
> and has done for ages.

It's hitting a simple limit. Please try the patch below - it 
quadruples the value printed in the warning (the number of entries) 
- does that get your system going?

Lock validation is getting more and more popular, covering now a lot 
more than just locks (workqueues, timers, etc.), so the max number 
of entries is steadily increasing. Some configs will run into this 
faster.

	Ingo

diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index 699a2ac..031f4c6 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -65,7 +65,7 @@ enum {
  * Stack-trace: tightly packed array of stack backtrace
  * addresses. Protected by the hash_lock.
  */
-#define MAX_STACK_TRACE_ENTRIES	262144UL
+#define MAX_STACK_TRACE_ENTRIES	1048576UL
 
 extern struct list_head all_lock_classes;
 extern struct lock_chain lock_chains[];
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