Remove debug yield statements

[urcu.git] / urcu.h

diff --git a/urcu.h b/urcu.h
index 7c94a776119245086fc6a5ea84cd35684e0b2d8f..1b663c7ff1492e3beeab7832a592e6c2b7d90925 100644 (file)
--- a/urcu.h
+++ b/urcu.h
@@ -17,8 +17,8 @@
  * Distributed under GPLv2
  */
 
-#define __USE_GNU
 #include <stdlib.h>
+#include <pthread.h>
 
 /* The "volatile" is due to gcc bugs */
 #define barrier() __asm__ __volatile__("": : :"memory")
@@ -31,6 +31,19 @@
 #define rmb()   asm volatile("lfence":::"memory")
 #define wmb()   asm volatile("sfence" ::: "memory")
 
+/* Assume SMP machine, given we don't have this information */
+#define CONFIG_SMP 1
+
+#ifdef CONFIG_SMP
+#define smp_mb()       mb()
+#define smp_rmb()      rmb()
+#define smp_wmb()      wmb()
+#else
+#define smp_mb()       barrier()
+#define smp_rmb()      barrier()
+#define smp_wmb()      barrier()
+#endif
+
 static inline void atomic_inc(int *v)
 {
        asm volatile("lock; incl %0"
@@ -121,10 +134,19 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
 #include <sched.h>
 #include <time.h>
 #include <pthread.h>
+#include <unistd.h>
 
 #define YIELD_READ     (1 << 0)
 #define YIELD_WRITE    (1 << 1)
 
+/* Updates without DEBUG_FULL_MB are much slower. Account this in the delay */
+#ifdef DEBUG_FULL_MB
+/* maximum sleep delay, in us */
+#define MAX_SLEEP 50
+#else
+#define MAX_SLEEP 30000
+#endif
+
 extern unsigned int yield_active;
 extern unsigned int __thread rand_yield;
 
@@ -132,14 +154,14 @@ static inline void debug_yield_read(void)
 {
        if (yield_active & YIELD_READ)
                if (rand_r(&rand_yield) & 0x1)
-                       sched_yield();
+                       usleep(rand_r(&rand_yield) % MAX_SLEEP);
 }
 
 static inline void debug_yield_write(void)
 {
        if (yield_active & YIELD_WRITE)
                if (rand_r(&rand_yield) & 0x1)
-                       sched_yield();
+                       usleep(rand_r(&rand_yield) % MAX_SLEEP);
 }
 
 static inline void debug_yield_init(void)
@@ -161,12 +183,25 @@ static inline void debug_yield_init(void)
 }
 #endif
 
+#ifdef DEBUG_FULL_MB
+static inline void read_barrier()
+{
+       smp_mb();
+}
+#else
+static inline void read_barrier()
+{
+       barrier();
+}
+#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)
 
 /*
@@ -174,54 +209,50 @@ static inline void debug_yield_init(void)
  * Using a int rather than a char to eliminate false register dependencies
  * causing stalls on some architectures.
  */
-extern int urcu_gp_ctr;
+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;
-       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 ^ ACCESS_ONCE(urcu_gp_ctr)) & RCU_GP_CTR_BIT);
+                ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT);
 }
 
 static inline void rcu_read_lock(void)
 {
-       int tmp;
+       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) */
        if (likely(!(tmp & RCU_GP_CTR_NEST_MASK)))
-               urcu_active_readers = urcu_gp_ctr + RCU_GP_COUNT;
+               urcu_active_readers = 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().
         */
-       barrier();
-       debug_yield_read();
+       read_barrier();
 }
 
 static inline void rcu_read_unlock(void)
 {
-       debug_yield_read();
-       barrier();
-       debug_yield_read();
+       read_barrier();
        /*
         * Finish using rcu before decrementing the pointer.
         * See force_mb_all_threads().
         */
        urcu_active_readers -= RCU_GP_COUNT;
-       debug_yield_read();
 }
 
 /**
@@ -262,7 +293,6 @@ extern void synchronize_rcu(void);
 #define urcu_publish_content(p, v) \
        ({ \
                void *oldptr; \
-               debug_yield_write(); \
                oldptr = rcu_xchg_pointer(p, v); \
                synchronize_rcu(); \
                oldptr; \