[PATCH tip/core/rcu 24/47] rcu: Check for idle-loop entry while in RCU read-side critical section

From: Paul E. McKenney
Date: Fri Feb 03 2012 - 20:56:39 EST

From: "Paul E. McKenney" <paul.mckenney@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
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)
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.");


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