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    SubjectRe: [PATCH 12/16] locking/mutex: Replace spin_is_locked() with lockdep
    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?

    Will

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