#define likely(x) __builtin_expect(!!(x), 1)
#define unlikely(x) __builtin_expect(!!(x), 0)
+/* Assume P4 or newer */
+#define CONFIG_HAS_FENCE 1
+
/* x86 32/64 specific */
+#ifdef CONFIG_HAS_FENCE
#define mb() asm volatile("mfence":::"memory")
#define rmb() asm volatile("lfence":::"memory")
-#define wmb() asm volatile("sfence" ::: "memory")
+#define wmb() asm volatile("sfence"::: "memory")
+#else
+/*
+ * Some non-Intel clones support out of order store. wmb() ceases to be a
+ * nop for these.
+ */
+#define mb() asm volatile("lock; addl $0,0(%%esp)":::"memory")
+#define rmb() asm volatile("lock; addl $0,0(%%esp)":::"memory")
+#define wmb() asm volatile("lock; addl $0,0(%%esp)"::: "memory")
+#endif
/* Assume SMP machine, given we don't have this information */
#define CONFIG_SMP 1
#define SIGURCU SIGUSR1
+/*
+ * If a reader is really non-cooperative and refuses to commit its
+ * urcu_active_readers 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
+
#ifdef DEBUG_YIELD
#include <sched.h>
#include <time.h>
if (value == NULL)
return 0;
- debug_yield_write();
/*
* Make sure both tests below are done on the same version of *value
* to insure consistency.
*/
v = ACCESS_ONCE(*value);
- debug_yield_write();
return (v & RCU_GP_CTR_NEST_MASK) &&
((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT);
}
{
long tmp;
- debug_yield_read();
tmp = urcu_active_readers;
- debug_yield_read();
/* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */
+ /* The data dependency "read urcu_gp_ctr, write urcu_active_readers",
+ * serializes those two memory operations. */
if (likely(!(tmp & RCU_GP_CTR_NEST_MASK)))
- urcu_active_readers = urcu_gp_ctr;
+ urcu_active_readers = ACCESS_ONCE(urcu_gp_ctr);
else
urcu_active_readers = tmp + RCU_GP_COUNT;
- debug_yield_read();
/*
* Increment active readers count before accessing the pointer.
* See force_mb_all_threads().
*/
read_barrier();
- debug_yield_read();
}
static inline void rcu_read_unlock(void)
{
- debug_yield_read();
read_barrier();
- debug_yield_read();
/*
* Finish using rcu before decrementing the pointer.
* See force_mb_all_threads().
*/
urcu_active_readers -= RCU_GP_COUNT;
- debug_yield_read();
}
/**
#define urcu_publish_content(p, v) \
({ \
void *oldptr; \
- debug_yield_write(); \
oldptr = rcu_xchg_pointer(p, v); \
synchronize_rcu(); \
oldptr; \