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Subject[PATCH RFC tip/core/rcu 03/14] rcu/nocb: EXP Check use and usefulness of ->nocb_lock_contended
Date
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
---
kernel/rcu/tree_plugin.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index bb906295538d..fcbd61738dff 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1513,6 +1513,7 @@ static void rcu_nocb_bypass_lock(struct rcu_data *rdp)
if (raw_spin_trylock(&rdp->nocb_bypass_lock))
return;
atomic_inc(&rdp->nocb_lock_contended);
+ WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
smp_mb__after_atomic(); /* atomic_inc() before lock. */
raw_spin_lock(&rdp->nocb_bypass_lock);
smp_mb__before_atomic(); /* atomic_dec() after lock. */
@@ -1531,7 +1532,8 @@ static void rcu_nocb_bypass_lock(struct rcu_data *rdp)
*/
static void rcu_nocb_wait_contended(struct rcu_data *rdp)
{
- while (atomic_read(&rdp->nocb_lock_contended))
+ WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
+ while (WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)))
cpu_relax();
}

--
2.17.1
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