X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=urcu%2Fstatic%2Furcu-bp.h;h=a2f73687d0a1995e5b3207b9f3fd3b970499d961;hb=a5a9f428a238e790d6c97299bc214b5cca815cd7;hp=64c32ea1ace5f14228e760f48383a47c03b8862d;hpb=bc2433a9853a945a825c244e9ccfe341b73b2ceb;p=urcu.git

diff --git a/urcu/static/urcu-bp.h b/urcu/static/urcu-bp.h
index 64c32ea..a2f7368 100644
--- a/urcu/static/urcu-bp.h
+++ b/urcu/static/urcu-bp.h
@@ -6,8 +6,8 @@
  *
  * Userspace RCU header.
  *
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
- * dynamically with the userspace rcu library.
+ * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
+ * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
  *
  * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
@@ -38,6 +38,7 @@
 #include <urcu/system.h>
 #include <urcu/uatomic.h>
 #include <urcu/list.h>
+#include <urcu/tls-compat.h>
 
 /*
  * This code section can only be included in LGPL 2.1 compatible source code.
@@ -51,11 +52,6 @@
 extern "C" {
 #endif
 
-/*
- * Active attempts to check for reader Q.S. before calling sleep().
- */
-#define RCU_QS_ACTIVE_ATTEMPTS 100
-
 #ifdef DEBUG_RCU
 #define rcu_assert(args...)	assert(args)
 #else
@@ -79,25 +75,25 @@ extern "C" {
 #define MAX_SLEEP 50
 
 extern unsigned int yield_active;
-extern unsigned int __thread rand_yield;
+extern DECLARE_URCU_TLS(unsigned int, rand_yield);
 
 static inline void debug_yield_read(void)
 {
 	if (yield_active & YIELD_READ)
-		if (rand_r(&rand_yield) & 0x1)
-			usleep(rand_r(&rand_yield) % MAX_SLEEP);
+		if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
+			usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
 }
 
 static inline void debug_yield_write(void)
 {
 	if (yield_active & YIELD_WRITE)
-		if (rand_r(&rand_yield) & 0x1)
-			usleep(rand_r(&rand_yield) % MAX_SLEEP);
+		if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
+			usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
 }
 
 static inline void debug_yield_init(void)
 {
-	rand_yield = time(NULL) ^ pthread_self();
+	URCU_TLS(rand_yield) = time(NULL) ^ pthread_self();
 }
 #else
 static inline void debug_yield_read(void)
@@ -149,7 +145,7 @@ struct rcu_reader {
  * Adds a pointer dereference on the read-side, but won't require to unregister
  * the reader thread.
  */
-extern struct rcu_reader __thread *rcu_reader;
+extern DECLARE_URCU_TLS(struct rcu_reader *, rcu_reader);
 
 static inline int rcu_old_gp_ongoing(long *value)
 {
@@ -166,39 +162,55 @@ static inline int rcu_old_gp_ongoing(long *value)
 		 ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE);
 }
 
+/*
+ * 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
+ * _rcu_read_lock() happen before the subsequent read-side critical section.
+ */
+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_smp_mb();
+	} else
+		_CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp + RCU_GP_COUNT);
+}
+
+/*
+ * Enter an RCU read-side critical section.
+ *
+ * The first cmm_barrier() call ensures that the compiler does not reorder
+ * the body of _rcu_read_lock() with a mutex.
+ *
+ * This function and its helper are both less than 10 lines long.  The
+ * intent is that this function meets the 10-line criterion in LGPL,
+ * allowing this function to be invoked directly from non-LGPL code.
+ */
 static inline void _rcu_read_lock(void)
 {
 	long tmp;
 
-	/* Check if registered */
-	if (unlikely(!rcu_reader))
-		rcu_bp_register();
-
+	if (caa_unlikely(!URCU_TLS(rcu_reader)))
+		rcu_bp_register(); /* If not yet registered. */
 	cmm_barrier();	/* Ensure the compiler does not reorder us with mutex */
-	tmp = rcu_reader->ctr;
-	/*
-	 * rcu_gp_ctr is
-	 *   RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE)
-	 */
-	if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
-		_CMM_STORE_SHARED(rcu_reader->ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
-		/*
-		 * Set active readers count for outermost nesting level before
-		 * accessing the pointer.
-		 */
-		cmm_smp_mb();
-	} else {
-		_CMM_STORE_SHARED(rcu_reader->ctr, tmp + RCU_GP_COUNT);
-	}
+	tmp = URCU_TLS(rcu_reader)->ctr;
+	_rcu_read_lock_update(tmp);
 }
 
+/*
+ * Exit an RCU read-side critical section.  This function is less than
+ * 10 lines of code, and is intended to be usable by non-LGPL code, as
+ * called out in LGPL.
+ */
 static inline void _rcu_read_unlock(void)
 {
 	/*
 	 * Finish using rcu before decrementing the pointer.
 	 */
 	cmm_smp_mb();
-	_CMM_STORE_SHARED(rcu_reader->ctr, rcu_reader->ctr - RCU_GP_COUNT);
+	_CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, URCU_TLS(rcu_reader)->ctr - RCU_GP_COUNT);
 	cmm_barrier();	/* Ensure the compiler does not reorder us with mutex */
 }