urcu-defer: fix futex wakeup value

[urcu.git] / urcu-qsbr-static.h

diff --git a/urcu-qsbr-static.h b/urcu-qsbr-static.h
index 8d8aa3f8f60519620dbcfb78aef1b007c6183e5c..c0467cd0e1606c87a522e56d2299716cf6402b3e 100644 (file)
--- a/urcu-qsbr-static.h
+++ b/urcu-qsbr-static.h
@@ -32,6 +32,7 @@
 #include <stdlib.h>
 #include <pthread.h>
 #include <assert.h>
+#include <limits.h>
 
 #include <compiler.h>
 #include <arch.h>
@@ -160,28 +161,43 @@ static inline void reader_barrier()
        smp_mb();
 }
 
+#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 long urcu_gp_ctr;
+extern unsigned long urcu_gp_ctr;
+
+extern unsigned long __thread rcu_reader_qs_gp;
 
-extern long __thread rcu_reader_qs_gp;
+#if (BITS_PER_LONG < 64)
+static inline int rcu_gp_ongoing(unsigned long *value)
+{
+       unsigned long reader_gp;
 
-static inline int rcu_gp_ongoing(long *value)
+       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)
 {
-       long reader_gp;
+       unsigned long reader_gp;
 
        if (value == NULL)
                return 0;
        reader_gp = LOAD_SHARED(*value);
-       return reader_gp && (reader_gp - urcu_gp_ctr < 0);
+       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 & 1);
+       rcu_assert(rcu_reader_qs_gp);
 }
 
 static inline void _rcu_read_unlock(void)
@@ -228,6 +244,22 @@ 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();                          \
+               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