X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;ds=sidebyside;f=urcu%2Fstatic%2Furcu-qsbr.h;h=690b77d528c38ef173aa1da91fc1d39dad0fed94;hb=4de0cd31491bcb93a19c14fc1eb2a2a23ce12855;hp=f3149569b2a2e2573df57936673d82eaadf0e1d7;hpb=f864c15d3148f14019e837544213314db0198ccb;p=urcu.git

diff --git a/urcu/static/urcu-qsbr.h b/urcu/static/urcu-qsbr.h
index f314956..690b77d 100644
--- a/urcu/static/urcu-qsbr.h
+++ b/urcu/static/urcu-qsbr.h
@@ -62,6 +62,12 @@ extern "C" {
 #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>
@@ -113,12 +119,18 @@ static inline void rcu_debug_yield_init(void)
 #define RCU_GP_ONLINE		(1UL << 0)
 #define RCU_GP_CTR		(1UL << 1)
 
-/*
- * Global quiescent period counter with low-order bits unused.
- * Using a int rather than a char to eliminate false register dependencies
- * causing stalls on some architectures.
- */
-extern unsigned long rcu_gp_ctr;
+struct rcu_gp {
+	/*
+	 * Global quiescent period counter with low-order bits unused.
+	 * Using a int rather than a char to eliminate false register
+	 * dependencies causing stalls on some architectures.
+	 */
+	unsigned long ctr;
+
+	int32_t futex;
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+
+extern struct rcu_gp rcu_gp;
 
 struct rcu_reader {
 	/* Data used by both reader and synchronize_rcu() */
@@ -131,8 +143,6 @@ struct rcu_reader {
 
 extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
 
-extern int32_t rcu_gp_futex;
-
 /*
  * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
  */
@@ -141,20 +151,24 @@ static inline void wake_up_gp(void)
 	if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader).waiting))) {
 		_CMM_STORE_SHARED(URCU_TLS(rcu_reader).waiting, 0);
 		cmm_smp_mb();
-		if (uatomic_read(&rcu_gp_futex) != -1)
+		if (uatomic_read(&rcu_gp.futex) != -1)
 			return;
-		uatomic_set(&rcu_gp_futex, 0);
-		futex_noasync(&rcu_gp_futex, FUTEX_WAKE, 1,
+		uatomic_set(&rcu_gp.futex, 0);
+		futex_noasync(&rcu_gp.futex, FUTEX_WAKE, 1,
 		      NULL, NULL, 0);
 	}
 }
 
-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;
 }
 
 /*
@@ -180,6 +194,18 @@ static inline void _rcu_read_unlock(void)
 {
 }
 
+/*
+ * 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 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
@@ -206,7 +232,7 @@ static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr)
  * 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
+ * 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.
  */
@@ -214,7 +240,7 @@ 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)
+	if ((gp_ctr = CMM_LOAD_SHARED(rcu_gp.ctr)) == URCU_TLS(rcu_reader).ctr)
 		return;
 	_rcu_quiescent_state_update_and_wakeup(gp_ctr);
 }
@@ -247,7 +273,7 @@ static inline void _rcu_thread_offline(void)
 static inline void _rcu_thread_online(void)
 {
 	cmm_barrier();	/* Ensure the compiler does not reorder us with mutex */
-	_CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
+	_CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp.ctr));
 	cmm_smp_mb();
 }