#include <pthread.h>
#include <assert.h>
#include <limits.h>
+#include <syscall.h>
+#include <unistd.h>
#include <compiler.h>
#include <arch.h>
(_________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
*/
#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
}
#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.
extern unsigned long __thread rcu_reader_qs_gp;
+extern int gp_futex;
+
+/*
+ * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
+ */
+static inline void wake_up_gp(void)
+{
+ if (unlikely(atomic_read(&gp_futex) == -1)) {
+ atomic_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;
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)
{
{
smp_mb();
_STORE_SHARED(rcu_reader_qs_gp, _LOAD_SHARED(urcu_gp_ctr));
+ smp_mb(); /* write rcu_reader_qs_gp before read futex */
+ wake_up_gp();
smp_mb();
}
{
smp_mb();
STORE_SHARED(rcu_reader_qs_gp, 0);
+ smp_mb(); /* write rcu_reader_qs_gp before read futex */
+ wake_up_gp();
}
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(); \
+ 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