X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.h;h=c4a7992b4b7b166d527411d4ae5108cac174fc95;hp=fb8cedf3e15beab5ba5355b153d0bb999fa1c7fc;hb=5464000f823e493703feb49d7580a479d3ba54d4;hpb=f4a486ac095bd844d0c18995737d589b8f085b69

diff --git a/urcu.h b/urcu.h
index fb8cedf..c4a7992 100644
--- a/urcu.h
+++ b/urcu.h
@@ -18,10 +18,14 @@
  */
 
 #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")
@@ -63,7 +67,13 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
 			     : "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");
@@ -109,10 +119,21 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
 
 #ifdef DEBUG_YIELD
 #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;
 
@@ -120,14 +141,14 @@ 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)
@@ -149,41 +170,63 @@ static inline void debug_yield_init(void)
 }
 #endif
 
+#ifdef DEBUG_FULL_MB
+static inline void read_barrier()
+{
+	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)
 
-/* 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;
 	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();
-	if (!(tmp & RCU_GP_CTR_NEST_MASK))
-		urcu_active_readers = urcu_gp_ctr + RCU_GP_COUNT;
+	/* 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;
 	else
 		urcu_active_readers = tmp + RCU_GP_COUNT;
 	debug_yield_read();
@@ -191,14 +234,14 @@ static inline void rcu_read_lock(void)
 	 * Increment active readers count before accessing the pointer.
 	 * See force_mb_all_threads().
 	 */
-	barrier();
+	read_barrier();
 	debug_yield_read();
 }
 
 static inline void rcu_read_unlock(void)
 {
 	debug_yield_read();
-	barrier();
+	read_barrier();
 	debug_yield_read();
 	/*
 	 * Finish using rcu before decrementing the pointer.