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SubjectRe: [PATCH 12/16] locking/mutex: Replace spin_is_locked() with lockdep
On Tue, Oct 09, 2018 at 01:18:10PM +0100, Will Deacon wrote:
> On Tue, Oct 02, 2018 at 10:38:58PM -0700, Lance Roy wrote:
> > lockdep_assert_held() is better suited to checking locking requirements,
> > since it won't get confused when someone else holds the lock. This is
> > also a step towards possibly removing spin_is_locked().
> >
> > Signed-off-by: Lance Roy <ldr709@gmail.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Will Deacon <will.deacon@arm.com>
> > ---
> > kernel/locking/mutex-debug.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
> > index 9aa713629387..771d4ca96dda 100644
> > --- a/kernel/locking/mutex-debug.c
> > +++ b/kernel/locking/mutex-debug.c
> > @@ -36,7 +36,7 @@ void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter)
> >
> > void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter)
> > {
> > - SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock));
> > + lockdep_assert_held(&lock->wait_lock);
> > DEBUG_LOCKS_WARN_ON(list_empty(&lock->wait_list));
> > DEBUG_LOCKS_WARN_ON(waiter->magic != waiter);
> > DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list));
> > @@ -51,7 +51,7 @@ void debug_mutex_free_waiter(struct mutex_waiter *waiter)
> > void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
> > struct task_struct *task)
> > {
> > - SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock));
> > + lockdep_assert_held(&lock->wait_lock);
>
> I think it's a good idea to replace debug usage of spin_is_locked() with
> calls to lockdep, but I wonder whether that means that DEBUG_MUTEXES should
> select LOCKDEP so that we don't lose coverage?
>
> What do you think?

Makes sense to me!

But given that this was accepted into -tip, I have dropped it from my tree.

Thanx, Paul

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