* Distributed under GPLv2
*/
+#include <stdlib.h>
+
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
#define YIELD_READ (1 << 0)
#define YIELD_WRITE (1 << 1)
-extern int yield_active;
+extern unsigned int yield_active;
+extern unsigned int __thread rand_yield;
static inline void debug_yield_read(void)
{
if (yield_active & YIELD_READ)
- sched_yield();
+ if (rand_r(&rand_yield) & 0x1)
+ sched_yield();
}
static inline void debug_yield_write(void)
{
if (yield_active & YIELD_WRITE)
- sched_yield();
+ if (rand_r(&rand_yield) & 0x1)
+ sched_yield();
+}
+
+static inline void debug_yield_init(void)
+{
+ rand_yield = time(NULL) ^ pthread_self();
}
#else
static inline void debug_yield_read(void)
static inline void debug_yield_write(void)
{
+}
+
+static inline void debug_yield_init(void)
+{
+
}
#endif
-/* Global quiescent period parity */
-extern int urcu_qparity;
+/*
+ * Limiting the nesting level to 256 to keep instructions small in the read
+ * fast-path.
+ */
+#define RCU_GP_COUNT (1U << 0)
+#define RCU_GP_CTR_BIT (1U << 8)
+#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
+
+/* Global quiescent period counter with low-order bits unused. */
+extern int urcu_gp_ctr;
-extern int __thread urcu_active_readers[2];
+extern int __thread urcu_active_readers;
-static inline int get_urcu_qparity(void)
+static inline int rcu_old_gp_ongoing(int *value)
{
- return urcu_qparity;
+ int v;
+
+ if (value == NULL)
+ return 0;
+ debug_yield_write();
+ v = ACCESS_ONCE(*value);
+ debug_yield_write();
+ return (v & RCU_GP_CTR_NEST_MASK) &&
+ ((v ^ ACCESS_ONCE(urcu_gp_ctr)) & RCU_GP_CTR_BIT);
}
-/*
- * urcu_parity should be declared on the caller's stack.
- */
-static inline void rcu_read_lock(int *urcu_parity)
+static inline void rcu_read_lock(void)
{
+ int tmp;
+
debug_yield_read();
- *urcu_parity = get_urcu_qparity();
+ tmp = urcu_active_readers;
debug_yield_read();
- urcu_active_readers[*urcu_parity]++;
+ if (!(tmp & RCU_GP_CTR_NEST_MASK))
+ urcu_active_readers = urcu_gp_ctr + RCU_GP_COUNT;
+ else
+ urcu_active_readers = tmp + RCU_GP_COUNT;
debug_yield_read();
/*
* Increment active readers count before accessing the pointer.
debug_yield_read();
}
-static inline void rcu_read_unlock(int *urcu_parity)
+static inline void rcu_read_unlock(void)
{
debug_yield_read();
barrier();
* Finish using rcu before decrementing the pointer.
* See force_mb_all_threads().
*/
- urcu_active_readers[*urcu_parity]--;
+ urcu_active_readers -= RCU_GP_COUNT;
debug_yield_read();
}