Detect RCU read-side underflows

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

diff --git a/urcu/static/urcu.h b/urcu/static/urcu.h
index fbba46cde9afdc6bff0c4b337a22afc78d40fea7..c44c137278301a9b02e5b0c13693968c95e75d03 100644 (file)
--- a/urcu/static/urcu.h
+++ b/urcu/static/urcu.h
@@ -239,11 +239,11 @@ static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
 {
        if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
                smp_mb_slave(RCU_MB_GROUP);
-               _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);
                smp_mb_slave(RCU_MB_GROUP);
                wake_up_gp();
        } else
-               _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);
 }
 
 /*
@@ -257,6 +257,7 @@ static inline void _rcu_read_unlock(void)
 
        urcu_assert(URCU_TLS(rcu_reader).registered);
        tmp = URCU_TLS(rcu_reader).ctr;
+       urcu_assert(tmp & RCU_GP_CTR_NEST_MASK);
        _rcu_read_unlock_update_and_wakeup(tmp);
        cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 }