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    Subject[PATCH] lockdep: annotate rcu_read_{,un}lock()
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    Date

    There seem to be some unbalanced rcu_read_{,un}lock() issues of late,
    how about doing something like this:

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    include/linux/lockdep.h | 7 +++++++
    include/linux/rcupdate.h | 12 ++++++++++++
    kernel/rcupdate.c | 8 ++++++++
    3 files changed, 27 insertions(+)

    Index: linux-2.6/include/linux/lockdep.h
    ===================================================================
    --- linux-2.6.orig/include/linux/lockdep.h
    +++ linux-2.6/include/linux/lockdep.h
    @@ -252,6 +252,13 @@ extern void lockdep_init_map(struct lock
    struct lock_class_key *key, int subclass);

    /*
    + * To initialize a lockdep_map statically use this macro.
    + * Note that _name must not be NULL.
    + */
    +#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
    + { .name = (_name), .key = (void *)(_key), }
    +
    +/*
    * Reinitialize a lock key - for cases where there is special locking or
    * special initialization of locks so that the validator gets the scope
    * of dependencies wrong: they are either too broad (they need a class-split)
    Index: linux-2.6/include/linux/rcupdate.h
    ===================================================================
    --- linux-2.6.orig/include/linux/rcupdate.h
    +++ linux-2.6/include/linux/rcupdate.h
    @@ -41,6 +41,7 @@
    #include <linux/percpu.h>
    #include <linux/cpumask.h>
    #include <linux/seqlock.h>
    +#include <linux/lockdep.h>

    /**
    * struct rcu_head - callback structure for use with RCU
    @@ -133,6 +134,15 @@ static inline void rcu_bh_qsctr_inc(int
    extern int rcu_pending(int cpu);
    extern int rcu_needs_cpu(int cpu);

    +#ifdef CONFIG_DEBUG_LOCK_ALLOC
    +extern struct lockdep_map rcu_lock_map;
    +# define rcu_read_acquire() lock_acquire(&rcu_lock_map, 0, 0, 2, 1, _THIS_IP_)
    +# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
    +#else
    +# define rcu_read_acquire() do { } while (0)
    +# define rcu_read_release() do { } while (0)
    +#endif
    +
    /**
    * rcu_read_lock - mark the beginning of an RCU read-side critical section.
    *
    @@ -166,6 +176,7 @@ extern int rcu_needs_cpu(int cpu);
    do { \
    preempt_disable(); \
    __acquire(RCU); \
    + rcu_read_acquire(); \
    } while(0)

    /**
    @@ -175,6 +186,7 @@ extern int rcu_needs_cpu(int cpu);
    */
    #define rcu_read_unlock() \
    do { \
    + rcu_read_release(); \
    __release(RCU); \
    preempt_enable(); \
    } while(0)
    Index: linux-2.6/kernel/rcupdate.c
    ===================================================================
    --- linux-2.6.orig/kernel/rcupdate.c
    +++ linux-2.6/kernel/rcupdate.c
    @@ -49,6 +49,14 @@
    #include <linux/cpu.h>
    #include <linux/mutex.h>

    +#ifdef CONFIG_DEBUG_LOCK_ALLOC
    +static struct lock_class_key rcu_lock_key;
    +struct lockdep_map rcu_lock_map =
    + STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
    +
    +EXPORT_SYMBOL_GPL(rcu_lock_map);
    +#endif
    +
    /* Definition for rcupdate control block. */
    static struct rcu_ctrlblk rcu_ctrlblk = {
    .cur = -300,

    -
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