Detect RCU read-side underflows

[urcu.git] / urcu / static / urcu-bp.h

diff --git a/urcu/static/urcu-bp.h b/urcu/static/urcu-bp.h
index 0fcaa3aa272806aa9c8786c96b7675de4fcfddd3..ffd4b8959b61e49c092fa7d72a3053d5223ab500 100644 (file)
--- a/urcu/static/urcu-bp.h
+++ b/urcu/static/urcu-bp.h
@@ -164,11 +164,13 @@ static inline void _rcu_read_lock(void)
  */
 static inline void _rcu_read_unlock(void)
 {
-       /*
-        * Finish using rcu before decrementing the pointer.
-        */
+       unsigned long tmp;
+
+       tmp = URCU_TLS(rcu_reader)->ctr;
+       urcu_assert(tmp & RCU_GP_CTR_NEST_MASK);
+       /* Finish using rcu before decrementing the pointer. */
        cmm_smp_mb();
-       _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, URCU_TLS(rcu_reader)->ctr - RCU_GP_COUNT);
+       _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp - RCU_GP_COUNT);
        cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 }