From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Mon, 6 May 2013 14:30:57 +0000 (-0400)
Subject: urcu-bp: introduce struct urcu_gp
X-Git-Tag: v0.8.0~83
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=c13c2e55160906ebe65756d8674558eda123912d;p=userspace-rcu.git

urcu-bp: introduce struct urcu_gp

Make urcu-bp similar to urcu-qsbr and other urcu flavors.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/urcu-bp.c b/urcu-bp.c
index 8207a41..ef1e687 100644
--- a/urcu-bp.c
+++ b/urcu-bp.c
@@ -109,13 +109,7 @@ unsigned int rcu_yield_active;
 DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
 #endif
 
-/*
- * Global grace period counter.
- * Contains the current RCU_GP_CTR_PHASE.
- * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
- * Written to only by writer with mutex taken. Read by both writer and readers.
- */
-unsigned long rcu_gp_ctr = RCU_GP_COUNT;
+struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
 
 /*
  * Pointer to registry elements. Written to only by each individual reader. Read
@@ -174,7 +168,7 @@ static void wait_for_readers(struct cds_list_head *input_readers,
 	/*
 	 * Wait for each thread URCU_TLS(rcu_reader).ctr to either
 	 * indicate quiescence (not nested), or observe the current
-	 * rcu_gp_ctr value.
+	 * rcu_gp.ctr value.
 	 */
 	for (;;) {
 		wait_loops++;
@@ -250,7 +244,7 @@ void synchronize_rcu(void)
 	cmm_smp_mb();
 
 	/* Switch parity: 0 -> 1, 1 -> 0 */
-	CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
+	CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE);
 
 	/*
 	 * Must commit qparity update to memory before waiting for other parity
diff --git a/urcu/map/urcu-bp.h b/urcu/map/urcu-bp.h
index 8c819a6..92863fe 100644
--- a/urcu/map/urcu-bp.h
+++ b/urcu/map/urcu-bp.h
@@ -46,8 +46,7 @@
 #define rcu_exit			rcu_exit_bp
 #define synchronize_rcu			synchronize_rcu_bp
 #define rcu_reader			rcu_reader_bp
-#define rcu_gp_ctr			rcu_gp_ctr_bp
-#define rcu_gp_futex			rcu_gp_futex_bp	/* unused */
+#define rcu_gp				rcu_gp_bp
 
 #define get_cpu_call_rcu_data		get_cpu_call_rcu_data_bp
 #define get_call_rcu_thread		get_call_rcu_thread_bp
diff --git a/urcu/static/urcu-bp.h b/urcu/static/urcu-bp.h
index 2f36520..1052c44 100644
--- a/urcu/static/urcu-bp.h
+++ b/urcu/static/urcu-bp.h
@@ -130,12 +130,18 @@ static inline void rcu_debug_yield_init(void)
  */
 extern void rcu_bp_register(void);
 
-/*
- * 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 grace period counter.
+	 * Contains the current RCU_GP_CTR_PHASE.
+	 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
+	 * Written to only by writer with mutex taken.
+	 * Read by both writer and readers.
+	 */
+	unsigned long ctr;
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+
+extern struct rcu_gp rcu_gp;
 
 struct rcu_reader {
 	/* Data used by both reader and synchronize_rcu() */
@@ -166,13 +172,13 @@ static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
 	v = CMM_LOAD_SHARED(*ctr);
 	if (!(v & RCU_GP_CTR_NEST_MASK))
 		return RCU_READER_INACTIVE;
-	if (!((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE))
+	if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE))
 		return RCU_READER_ACTIVE_CURRENT;
 	return RCU_READER_ACTIVE_OLD;
 }
 
 /*
- * Helper for _rcu_read_lock().  The format of rcu_gp_ctr (as well as
+ * Helper for _rcu_read_lock().  The format of rcu_gp.ctr (as well as
  * the per-thread rcu_reader.ctr) has the upper bits containing a count of
  * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
  * or RCU_GP_CTR_PHASE.  The smp_mb_slave() ensures that the accesses in
@@ -181,7 +187,7 @@ static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
 static inline void _rcu_read_lock_update(unsigned long tmp)
 {
 	if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
-		_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();
 	} else
 		_CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp + RCU_GP_COUNT);