#define rcu_assert(args...)
#endif
+enum rcu_state {
+ RCU_READER_ACTIVE_CURRENT,
+ RCU_READER_ACTIVE_OLD,
+ RCU_READER_INACTIVE,
+};
+
#ifdef DEBUG_YIELD
#include <sched.h>
#include <time.h>
}
}
-static inline int rcu_gp_ongoing(unsigned long *ctr)
+static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
{
unsigned long v;
v = CMM_LOAD_SHARED(*ctr);
- return v && (v != rcu_gp_ctr);
+ if (!v)
+ return RCU_READER_INACTIVE;
+ if (v == rcu_gp_ctr)
+ return RCU_READER_ACTIVE_CURRENT;
+ return RCU_READER_ACTIVE_OLD;
}
/*
}
/*
- * Inform RCU of a quiescent state.
+ * Returns whether within a RCU read-side critical section.
*
* This function is less than 10 lines long. The intent is that this
* function meets the 10-line criterion for LGPL, allowing this function
* to be invoked directly from non-LGPL code.
*/
-static inline void _rcu_quiescent_state(void)
+static inline int _rcu_read_ongoing(void)
+{
+ return URCU_TLS(rcu_reader).ctr;
+}
+
+/*
+ * This is a helper function for _rcu_quiescent_state().
+ * The first cmm_smp_mb() ensures memory accesses in the prior read-side
+ * critical sections are not reordered with store to
+ * URCU_TLS(rcu_reader).ctr, and ensures that mutexes held within an
+ * offline section that would happen to end with this
+ * rcu_quiescent_state() call are not reordered with
+ * store to URCU_TLS(rcu_reader).ctr.
+ */
+static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr)
{
cmm_smp_mb();
- _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, gp_ctr);
cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
wake_up_gp();
cmm_smp_mb();
}
+/*
+ * Inform RCU of a quiescent state.
+ *
+ * This function is less than 10 lines long. The intent is that this
+ * function meets the 10-line criterion for LGPL, allowing this function
+ * to be invoked directly from non-LGPL code.
+ *
+ * We skip the memory barriers and gp store if our local ctr already
+ * matches the global rcu_gp_ctr value: this is OK because a prior
+ * _rcu_quiescent_state() or _rcu_thread_online() already updated it
+ * within our thread, so we have no quiescent state to report.
+ */
+static inline void _rcu_quiescent_state(void)
+{
+ unsigned long gp_ctr;
+
+ if ((gp_ctr = CMM_LOAD_SHARED(rcu_gp_ctr)) == URCU_TLS(rcu_reader).ctr)
+ return;
+ _rcu_quiescent_state_update_and_wakeup(gp_ctr);
+}
+
/*
* Take a thread offline, prohibiting it from entering further RCU
* read-side critical sections.