*/
#include <stdlib.h>
+#include <pthread.h>
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
+#define likely(x) __builtin_expect(!!(x), 1)
+#define unlikely(x) __builtin_expect(!!(x), 0)
+
/* x86 32/64 specific */
#define mb() asm volatile("mfence":::"memory")
#define rmb() asm volatile("lfence":::"memory")
: "memory");
break;
case 4:
- asm volatile("xchgl %0,%1"
+ asm volatile("xchgl %k0,%1"
+ : "=r" (x)
+ : "m" (*__xg(ptr)), "0" (x)
+ : "memory");
+ break;
+ case 8:
+ asm volatile("xchgq %0,%1"
: "=r" (x)
: "m" (*__xg(ptr)), "0" (x)
: "memory");
#ifdef DEBUG_YIELD
#include <sched.h>
+#include <time.h>
+#include <pthread.h>
#define YIELD_READ (1 << 0)
#define YIELD_WRITE (1 << 1)
#endif
/*
- * Limiting the nesting level to 256 to keep instructions small in the read
- * fast-path.
+ * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a
+ * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
*/
-#define RCU_GP_COUNT (1U << 0)
-#define RCU_GP_CTR_BIT (1U << 8)
+#define RCU_GP_COUNT (1UL << 0)
+/* Use the amount of bits equal to half of the architecture long size */
+#define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2))
#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;
+/*
+ * 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 int __thread urcu_active_readers;
+extern long __thread urcu_active_readers;
-static inline int rcu_old_gp_ongoing(int *value)
+static inline int rcu_old_gp_ongoing(long *value)
{
- int v;
+ long v;
if (value == NULL)
return 0;
static inline void rcu_read_lock(void)
{
- int tmp;
+ long tmp;
debug_yield_read();
tmp = urcu_active_readers;
debug_yield_read();
- if (!(tmp & RCU_GP_CTR_NEST_MASK))
- urcu_active_readers = urcu_gp_ctr + RCU_GP_COUNT;
+ if (likely(!(tmp & RCU_GP_CTR_NEST_MASK)))
+ urcu_active_readers = urcu_gp_ctr;
else
urcu_active_readers = tmp + RCU_GP_COUNT;
debug_yield_read();