[PATCH] lockdep: fix spurious 'inconsistent lock state' warning

[PATCH] lockdep: fix spurious 'inconsistent lock state' warning

[Dmitry Baryshkov]

Since f82b217e3513fe3af342c0f3ee1494e86250c21c lockdep can output spurious
warnings related to hwirqs due to hardirq_off shrinkage from int to bit-sized
flag. Guard it with double negation to fix the warning.

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
---
 kernel/lockdep.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 1aa91fd..b298888 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2584,7 +2584,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	hlock->trylock = trylock;
 	hlock->read = read;
 	hlock->check = check;
-	hlock->hardirqs_off = hardirqs_off;
+	hlock->hardirqs_off = !!hardirqs_off;
 #ifdef CONFIG_LOCK_STAT
 	hlock->waittime_stamp = 0;
 	hlock->holdtime_stamp = sched_clock();
-- 
1.5.6.3

Re: [PATCH] lockdep: fix spurious 'inconsistent lock state' warning

[Ingo Molnar]

* Dmitry Baryshkov <dbaryshkov@gmail.com> wrote:

> Since f82b217e3513fe3af342c0f3ee1494e86250c21c lockdep can output 
> spurious warnings related to hwirqs due to hardirq_off shrinkage from 
> int to bit-sized flag. Guard it with double negation to fix the 
> warning.
> 
> Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>

good spotting! Applied to tip/core/urgent, thanks Dmitry.

I'm wondering, is there any way to teach gcc some sanity here - a safer 
variant of bitfields, that is just not allowed to overflow into or 
corrupt nearby fields? The fact that a benign looking hlock->state = 15 
can corrupt other fields worries me quite a bit. Valid C semantics or 
not, this is a totally dangerous construct. The space savings are very 
real though, so it would be nice to get 'safer bitfields', somehow.

	Ingo