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    Subject[PATCH 08/13] lockdep: Introduce lockdep_assert_held()
    Add a lockdep helper to validate that we indeed are the owner of a
    lock.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    include/linux/lockdep.h | 8 ++++++++
    kernel/lockdep.c | 33 +++++++++++++++++++++++++++++++++
    kernel/sched.c | 2 ++
    3 files changed, 43 insertions(+)

    Index: linux-2.6/include/linux/lockdep.h
    ===================================================================
    --- linux-2.6.orig/include/linux/lockdep.h
    +++ linux-2.6/include/linux/lockdep.h
    @@ -296,6 +296,10 @@ extern void lock_acquire(struct lockdep_
    extern void lock_release(struct lockdep_map *lock, int nested,
    unsigned long ip);

    +#define lockdep_is_held(lock) lock_is_held(&(lock)->dep_map)
    +
    +extern int lock_is_held(struct lockdep_map *lock);
    +
    extern void lock_set_class(struct lockdep_map *lock, const char *name,
    struct lock_class_key *key, unsigned int subclass,
    unsigned long ip);
    @@ -314,6 +318,8 @@ extern void lockdep_trace_alloc(gfp_t ma

    #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)

    +#define lockdep_assert_held(l) WARN_ON(debug_locks && !lockdep_is_held(l))
    +
    #else /* !LOCKDEP */

    static inline void lockdep_off(void)
    @@ -358,6 +364,8 @@ struct lock_class_key { };

    #define lockdep_depth(tsk) (0)

    +#define lockdep_assert_held(l) do { } while (0)
    +
    #endif /* !LOCKDEP */

    #ifdef CONFIG_LOCK_STAT
    Index: linux-2.6/kernel/lockdep.c
    ===================================================================
    --- linux-2.6.orig/kernel/lockdep.c
    +++ linux-2.6/kernel/lockdep.c
    @@ -3044,6 +3044,19 @@ __lock_release(struct lockdep_map *lock,
    check_chain_key(curr);
    }

    +static int __lock_is_held(struct lockdep_map *lock)
    +{
    + struct task_struct *curr = current;
    + int i;
    +
    + for (i = 0; i < curr->lockdep_depth; i++) {
    + if (curr->held_locks[i].instance == lock)
    + return 1;
    + }
    +
    + return 0;
    +}
    +
    /*
    * Check whether we follow the irq-flags state precisely:
    */
    @@ -3145,6 +3158,26 @@ void lock_release(struct lockdep_map *lo
    }
    EXPORT_SYMBOL_GPL(lock_release);

    +int lock_is_held(struct lockdep_map *lock)
    +{
    + unsigned long flags;
    + int ret = 0;
    +
    + if (unlikely(current->lockdep_recursion))
    + return ret;
    +
    + raw_local_irq_save(flags);
    + check_flags(flags);
    +
    + current->lockdep_recursion = 1;
    + ret = __lock_is_held(lock);
    + current->lockdep_recursion = 0;
    + raw_local_irq_restore(flags);
    +
    + return ret;
    +}
    +EXPORT_SYMBOL_GPL(lock_is_held);
    +
    void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
    {
    current->lockdep_reclaim_gfp = gfp_mask;
    Index: linux-2.6/kernel/sched.c
    ===================================================================
    --- linux-2.6.orig/kernel/sched.c
    +++ linux-2.6/kernel/sched.c
    @@ -6648,6 +6648,8 @@ int cond_resched_lock(spinlock_t *lock)
    int resched = should_resched();
    int ret = 0;

    + lockdep_assert_held(lock);
    +
    if (spin_needbreak(lock) || resched) {
    spin_unlock(lock);
    if (resched)
    --



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