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

* Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> On Mon, 15 Jun 2009 16:39:56 +0200
> Peter Zijlstra <peterz@infradead.org> 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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