Re: lockdep oddity

Ingo Molnar
2006-09-06T10:13:28Z

* Heiko Carstens <heiko.carstens@de.ibm.com> wrote:

> That seems to be code that isn't upstream. 2.6.18-rc5-mm1 as well as
> Linus' current git tree have this:
>
> /*
> * If lockdep is enabled then we use the non-preemption spin-ops
> * even on CONFIG_PREEMPT, because lockdep assumes that interrupts are
> * not re-enabled during lock-acquire (which the preempt-spin-ops do):
> */
> #if !defined(CONFIG_PREEMPT) || !defined(CONFIG_SMP) || \
> defined(CONFIG_PROVE_LOCKING)
>
> And yes, using CONFIG_DEBUG_LOCK_ALLOC instead of CONFIG_PROVE_LOCKING
> fixes this for me :)

indeed, this is a very recent fix from Jarek Poplawski - not yet in
Linus' tree but already in Andrew's.

Ingo

---------->
From: Jarek Poplawski <jarkao2@o2.pl>

With

CONFIG_SMP=y
CONFIG_PREEMPT=y
CONFIG_LOCKDEP=y
CONFIG_DEBUG_LOCK_ALLOC=y
# CONFIG_PROVE_LOCKING is not set

spin_unlock_irqrestore() goes through lockdep but spin_lock_irqsave() doesn't.
Apparently, bad things happen.

Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

kernel/spinlock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN kernel/spinlock.c~lockdep-ifdef-fix kernel/spinlock.c
--- a/kernel/spinlock.c~lockdep-ifdef-fix
+++ a/kernel/spinlock.c
@@ -72,7 +72,7 @@ EXPORT_SYMBOL(_write_trylock);
* not re-enabled during lock-acquire (which the preempt-spin-ops do):
*/
#if !defined(CONFIG_PREEMPT) || !defined(CONFIG_SMP) || \
- defined(CONFIG_PROVE_LOCKING)
+ defined(CONFIG_DEBUG_LOCK_ALLOC)

void __lockfunc _read_lock(rwlock_t *lock)
{
_