X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=urcu.h;h=79d9464b0be63142fb51cb2f00d11edb5996441d;hb=b0b31506add8085c1f8839915f8e322d05d4fa4b;hp=1b663c7ff1492e3beeab7832a592e6c2b7d90925;hpb=ae878d0dcc291dba7c5722eed13294195a64409e;p=urcu.git

diff --git a/urcu.h b/urcu.h
index 1b663c7..79d9464 100644
--- a/urcu.h
+++ b/urcu.h
@@ -130,6 +130,13 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
 
 #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>
@@ -234,8 +241,10 @@ static inline void rcu_read_lock(void)
 
 	tmp = urcu_active_readers;
 	/* 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;
 	/*