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    Subject[PATCH tip/core/rcu 24/47] rcu: Check for idle-loop entry while in RCU read-side critical section
    Date
    From: "Paul E. McKenney" <paul.mckenney@linaro.org>

    The inner idle loop is an extended quiescent state for all flavors
    of RCU, but there have been recent bug involving use of RCU read-side
    primitives from within the idle loop. Therefore, this commit enlists
    lockdep-RCU to detect attempts to enter the inner idle loop while in
    an RCU read-side critical section, emitting a lockdep-RCU splat if so.

    Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    kernel/rcutree.c | 11 +++++++++++
    1 files changed, 11 insertions(+), 0 deletions(-)

    diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    index 0569ba1..195bf1f 100644
    --- a/kernel/rcutree.c
    +++ b/kernel/rcutree.c
    @@ -366,6 +366,17 @@ static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
    atomic_inc(&rdtp->dynticks);
    smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
    WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
    +
    + /*
    + * The idle task is not permitted to enter the idle loop while
    + * in an RCU read-side critical section.
    + */
    + rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
    + "Illegal idle entry in RCU read-side critical section.");
    + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),
    + "Illegal idle entry in RCU-bh read-side critical section.");
    + rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),
    + "Illegal idle entry in RCU-sched read-side critical section.");
    }

    /**
    --
    1.7.8


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