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    Subject[PATCH tip/core/rcu 02/18] rcu: add lockdep-enabled variants of rcu_dereference()
    Date
    Make rcu_dereference() check for being in an RCU read-side critical
    section, and create rcu_dereference_bh(), rcu_dereference_sched(), and
    srcu_dereference() to check for the other flavors of RCU. Also create
    rcu_dereference_raw() to avoid checking, and make rcu_dereference_check()
    use rcu_dereference_raw().

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    include/linux/rcupdate.h | 41 ++++++++++++++++++++++++++++++++++-------
    include/linux/srcu.h | 8 ++++++++
    2 files changed, 42 insertions(+), 7 deletions(-)
    diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
    index e3d37ef..839d296 100644
    --- a/include/linux/rcupdate.h
    +++ b/include/linux/rcupdate.h
    @@ -184,12 +184,12 @@ static inline int rcu_read_lock_sched_held(void)
    ({ \
    if (debug_locks) \
    WARN_ON_ONCE(!(c)); \
    - rcu_dereference(p); \
    + rcu_dereference_raw(p); \
    })

    #else /* #ifdef CONFIG_PROVE_RCU */

    -#define rcu_dereference_check(p, c) rcu_dereference(p)
    +#define rcu_dereference_check(p, c) rcu_dereference_raw(p)

    #endif /* #else #ifdef CONFIG_PROVE_RCU */

    @@ -325,22 +325,49 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)


    /**
    - * rcu_dereference - fetch an RCU-protected pointer in an
    - * RCU read-side critical section. This pointer may later
    - * be safely dereferenced.
    + * rcu_dereference_raw - fetch an RCU-protected pointer
    + *
    + * The caller must be within some flavor of RCU read-side critical
    + * section, or must be otherwise preventing the pointer from changing,
    + * for example, by holding an appropriate lock. This pointer may later
    + * be safely dereferenced. It is the caller's responsibility to have
    + * done the right thing, as this primitive does no checking of any kind.
    *
    * Inserts memory barriers on architectures that require them
    * (currently only the Alpha), and, more importantly, documents
    * exactly which pointers are protected by RCU.
    */
    -
    -#define rcu_dereference(p) ({ \
    +#define rcu_dereference_raw(p) ({ \
    typeof(p) _________p1 = ACCESS_ONCE(p); \
    smp_read_barrier_depends(); \
    (_________p1); \
    })

    /**
    + * rcu_dereference - fetch an RCU-protected pointer, checking for RCU
    + *
    + * Makes rcu_dereference_check() do the dirty work.
    + */
    +#define rcu_dereference(p) \
    + rcu_dereference_check(p, rcu_read_lock_held())
    +
    +/**
    + * rcu_dereference_bh - fetch an RCU-protected pointer, checking for RCU-bh
    + *
    + * Makes rcu_dereference_check() do the dirty work.
    + */
    +#define rcu_dereference_bh(p) \
    + rcu_dereference_check(p, rcu_read_lock_bh_held())
    +
    +/**
    + * rcu_dereference_sched - fetch RCU-protected pointer, checking for RCU-sched
    + *
    + * Makes rcu_dereference_check() do the dirty work.
    + */
    +#define rcu_dereference_sched(p) \
    + rcu_dereference_check(p, rcu_read_lock_sched_held())
    +
    +/**
    * rcu_assign_pointer - assign (publicize) a pointer to a newly
    * initialized structure that will be dereferenced by RCU read-side
    * critical sections. Returns the value assigned.
    diff --git a/include/linux/srcu.h b/include/linux/srcu.h
    index adbe167..3084f80 100644
    --- a/include/linux/srcu.h
    +++ b/include/linux/srcu.h
    @@ -106,6 +106,14 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp)
    #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */

    /**
    + * srcu_dereference - fetch SRCU-protected pointer with checking
    + *
    + * Makes rcu_dereference_check() do the dirty work.
    + */
    +#define srcu_dereference(p, sp) \
    + rcu_dereference_check(p, srcu_read_lock_held(sp))
    +
    +/**
    * srcu_read_lock - register a new reader for an SRCU-protected structure.
    * @sp: srcu_struct in which to register the new reader.
    *
    --
    1.6.6


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