X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=urcu-qsbr-static.h;h=d53a1f4919569e5ada46b6fd3ff83bc8bded341f;hp=887dc3d64e949ab843a248846e4286b4fbdbf7bb;hb=074d8438a30f7da8ae12eb94caff69c37fb576bd;hpb=ac258107eb2e669d6f8210c86164f1b2a028f5fc

diff --git a/urcu-qsbr-static.h b/urcu-qsbr-static.h
index 887dc3d..d53a1f4 100644
--- a/urcu-qsbr-static.h
+++ b/urcu-qsbr-static.h
@@ -33,9 +33,13 @@
 #include <pthread.h>
 #include <assert.h>
 #include <limits.h>
+#include <syscall.h>
+#include <unistd.h>
 
-#include <compiler.h>
-#include <arch.h>
+#include <urcu/compiler.h>
+#include <urcu/arch.h>
+#include <urcu/arch_uatomic.h>
+#include <urcu/list.h>
 
 /*
  * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
@@ -87,6 +91,10 @@
 				(_________p1);				\
 				})
 
+#define futex(...)		syscall(__NR_futex, __VA_ARGS__)
+#define FUTEX_WAIT		0
+#define FUTEX_WAKE		1
+
 /*
  * This code section can only be included in LGPL 2.1 compatible source code.
  * See below for the function call wrappers which can be used in code meant to
@@ -97,11 +105,16 @@
 
 /*
  * If a reader is really non-cooperative and refuses to commit its
- * rcu_reader_qs_gp count to memory (there is no barrier in the reader
+ * urcu_reader.ctr count to memory (there is no barrier in the reader
  * per-se), kick it after a few loops waiting for it.
  */
 #define KICK_READER_LOOPS 10000
 
+/*
+ * Active attempts to check for reader Q.S. before calling futex().
+ */
+#define RCU_QS_ACTIVE_ATTEMPTS 100
+
 #ifdef DEBUG_RCU
 #define rcu_assert(args...)	assert(args)
 #else
@@ -162,7 +175,7 @@ static inline void reader_barrier()
 }
 
 #define RCU_GP_ONLINE		(1UL << 0)
-#define RCU_GP_COUNT		(1UL << 1)
+#define RCU_GP_CTR		(1UL << 1)
 
 /*
  * Global quiescent period counter with low-order bits unused.
@@ -171,8 +184,41 @@ static inline void reader_barrier()
  */
 extern unsigned long urcu_gp_ctr;
 
-extern unsigned long __thread rcu_reader_qs_gp;
+struct urcu_reader {
+	/* Data used by both reader and synchronize_rcu() */
+	unsigned long ctr;
+	/* Data used for registry */
+	struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
+	pthread_t tid;
+};
+
+extern struct urcu_reader __thread urcu_reader;
+
+extern int gp_futex;
 
+/*
+ * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
+ */
+static inline void wake_up_gp(void)
+{
+	if (unlikely(uatomic_read(&gp_futex) == -1)) {
+		uatomic_set(&gp_futex, 0);
+		futex(&gp_futex, FUTEX_WAKE, 1,
+		      NULL, NULL, 0);
+	}
+}
+
+#if (BITS_PER_LONG < 64)
+static inline int rcu_gp_ongoing(unsigned long *value)
+{
+	unsigned long reader_gp;
+
+	if (value == NULL)
+		return 0;
+	reader_gp = LOAD_SHARED(*value);
+	return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
+}
+#else /* !(BITS_PER_LONG < 64) */
 static inline int rcu_gp_ongoing(unsigned long *value)
 {
 	unsigned long reader_gp;
@@ -182,10 +228,11 @@ static inline int rcu_gp_ongoing(unsigned long *value)
 	reader_gp = LOAD_SHARED(*value);
 	return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
 }
+#endif  /* !(BITS_PER_LONG < 64) */
 
 static inline void _rcu_read_lock(void)
 {
-	rcu_assert(rcu_reader_qs_gp);
+	rcu_assert(urcu_reader.ctr);
 }
 
 static inline void _rcu_read_unlock(void)
@@ -195,19 +242,23 @@ static inline void _rcu_read_unlock(void)
 static inline void _rcu_quiescent_state(void)
 {
 	smp_mb();	
-	_STORE_SHARED(rcu_reader_qs_gp, _LOAD_SHARED(urcu_gp_ctr));
+	_STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
+	smp_mb();	/* write urcu_reader.ctr before read futex */
+	wake_up_gp();
 	smp_mb();
 }
 
 static inline void _rcu_thread_offline(void)
 {
 	smp_mb();
-	STORE_SHARED(rcu_reader_qs_gp, 0);
+	STORE_SHARED(urcu_reader.ctr, 0);
+	smp_mb();	/* write urcu_reader.ctr before read futex */
+	wake_up_gp();
 }
 
 static inline void _rcu_thread_online(void)
 {
-	_STORE_SHARED(rcu_reader_qs_gp, LOAD_SHARED(urcu_gp_ctr));
+	_STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr));
 	smp_mb();
 }
 
@@ -232,6 +283,22 @@ static inline void _rcu_thread_online(void)
 		STORE_SHARED(p, v);			\
 	})
 
+/**
+ * _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer
+ * is as expected by "old". If succeeds, returns the previous pointer to the
+ * data structure, which can be safely freed after waiting for a quiescent state
+ * using synchronize_rcu(). If fails (unexpected value), returns old (which
+ * should not be freed !).
+ */
+
+#define _rcu_cmpxchg_pointer(p, old, _new)		\
+	({						\
+		if (!__builtin_constant_p(_new) ||	\
+		    ((_new) != NULL))			\
+			wmb();				\
+		uatomic_cmpxchg(p, old, _new);		\
+	})
+
 /**
  * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
  * pointer to the data structure, which can be safely freed after waiting for a
@@ -243,7 +310,7 @@ static inline void _rcu_thread_online(void)
 		if (!__builtin_constant_p(v) ||		\
 		    ((v) != NULL))			\
 			wmb();				\
-		xchg(p, v);				\
+		uatomic_xchg(p, v);			\
 	})
 
 /*