Merge branch 'atomic-ref'

Adds support for GCC's __atomic* built-ins and improves the performance
of logging (for ignored log levels) and half-open IKE_SA checking under
high loads.

Also fixes two potential race conditions in the load-tester plugin.

configure.ac

@@ -667,21 +667,39 @@ AC_COMPILE_IFELSE(
 	[AC_MSG_RESULT([no])]
 )
 
-AC_MSG_CHECKING([for gcc atomic operations])
+AC_MSG_CHECKING([for GCC __atomic operations])
 AC_RUN_IFELSE([AC_LANG_SOURCE(
 	[[
 			int main() {
-			volatile int ref = 1;
-			__sync_fetch_and_add (&ref, 1);
-			__sync_sub_and_fetch (&ref, 1);
-			/* Make sure test fails if operations are not supported */
-			__sync_val_compare_and_swap(&ref, 1, 0);
+			int ref = 1, val;
+			__atomic_fetch_add(&ref, 1, __ATOMIC_RELAXED);
+			val = __atomic_sub_fetch(&ref, 1, __ATOMIC_RELAXED);
+			__atomic_compare_exchange_n(&ref, &val, 0, 0, __ATOMIC_RELAXED,
+										__ATOMIC_RELAXED);
 			return ref;
 		}
 	]])],
 	[AC_MSG_RESULT([yes]);
 	 AC_DEFINE([HAVE_GCC_ATOMIC_OPERATIONS], [],
-		   [have GCC __sync_* atomic operations])],
+		   [have GCC __atomic_* operations])],
+	[AC_MSG_RESULT([no])],
+	[AC_MSG_RESULT([no])]
+)
+
+AC_MSG_CHECKING([for GCC __sync operations])
+AC_RUN_IFELSE([AC_LANG_SOURCE(
+	[[
+			int main() {
+			int ref = 1;
+			__sync_fetch_and_add (&ref, 1);
+			__sync_sub_and_fetch (&ref, 1);
+			__sync_val_compare_and_swap(&ref, 1, 0);
+			return ref;
+		}
+	]])],
+	[AC_MSG_RESULT([yes]);
+	 AC_DEFINE([HAVE_GCC_SYNC_OPERATIONS], [],
+		   [have GCC __sync_* operations])],
 	[AC_MSG_RESULT([no])],
 	[AC_MSG_RESULT([no])]
 )

src/libcharon/bus/bus.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011-2012 Tobias Brunner
+ * Copyright (C) 2011-2014 Tobias Brunner
  * Copyright (C) 2006 Martin Willi
  * Hochschule fuer Technik Rapperswil
  *
@@ -23,6 +23,31 @@
 #include <threading/mutex.h>
 #include <threading/rwlock.h>
 
+/**
+ * These operations allow us to speed up the log level checks on some platforms.
+ * In particular if acquiring the read lock is expensive even in the absence of
+ * any writers.
+ *
+ * Note that while holding the read/write lock the read does not have to be
+ * atomic as the write lock must be held to set the level.
+ */
+#ifdef HAVE_GCC_ATOMIC_OPERATIONS
+
+#define skip_level(ptr, level) (__atomic_load_n(ptr, __ATOMIC_RELAXED) < level)
+#define set_level(ptr, val) __atomic_store_n(ptr, val, __ATOMIC_RELAXED)
+
+#elif defined(HAVE_GCC_SYNC_OPERATIONS)
+
+#define skip_level(ptr, level) (__sync_fetch_and_add(ptr, 0) < level)
+#define set_level(ptr, val) __sync_bool_compare_and_swap(ptr, *ptr, val)
+
+#else
+
+#define skip_level(ptr, level) FALSE
+#define set_level(ptr, val) ({ *ptr = val; })
+
+#endif
+
 typedef struct private_bus_t private_bus_t;
 
 /**
@@ -173,11 +198,12 @@ static inline void register_logger(private_bus_t *this, debug_t group,
 
 	if (entry->logger->log)
 	{
-		this->max_level[group] = max(this->max_level[group], level);
+		set_level(&this->max_level[group], max(this->max_level[group], level));
 	}
 	if (entry->logger->vlog)
 	{
-		this->max_vlevel[group] = max(this->max_vlevel[group], level);
+		set_level(&this->max_vlevel[group],
+				  max(this->max_vlevel[group], level));
 	}
 }
 
@@ -205,6 +231,7 @@ static inline void unregister_logger(private_bus_t *this, logger_t *logger)
 
 	if (found)
 	{
+		level_t level = LEVEL_SILENT, vlevel = LEVEL_SILENT;
 		debug_t group;
 
 		for (group = 0; group < DBG_MAX; group++)
@@ -214,13 +241,19 @@ static inline void unregister_logger(private_bus_t *this, logger_t *logger)
 				loggers = this->loggers[group];
 				loggers->remove(loggers, found, NULL);
 
-				this->max_level[group] = LEVEL_SILENT;
-				this->max_vlevel[group] = LEVEL_SILENT;
 				if (loggers->get_first(loggers, (void**)&entry) == SUCCESS)
 				{
-					this->max_level[group] = entry->levels[group];
-					this->max_vlevel[group] = entry->levels[group];
+					if (entry->logger->log)
+					{
+						level = entry->levels[group];
+					}
+					if (entry->logger->vlog)
+					{
+						vlevel = entry->levels[group];
+					}
 				}
+				set_level(&this->max_level[group], level);
+				set_level(&this->max_vlevel[group], vlevel);
 			}
 		}
 		free(found);
@@ -324,6 +357,19 @@ METHOD(bus_t, vlog, void,
 	linked_list_t *loggers;
 	log_data_t data;
 
+	/* NOTE: This is not 100% thread-safe and done here only because it is
+	 * performance critical.  We therefore ignore the following two issues for
+	 * this particular case:  1) We might miss some log messages if another
+	 * thread concurrently increases the log level or registers a new logger.
+	 * 2) We might have to acquire the read lock below even if it wouldn't be
+	 * necessary anymore due to another thread concurrently unregistering a
+	 * logger or reducing the level. */
+	if (skip_level(&this->max_level[group], level) &&
+		skip_level(&this->max_vlevel[group], level))
+	{
+		return;
+	}
+
 	this->log_lock->read_lock(this->log_lock);
 	loggers = this->loggers[group];
 

src/libcharon/plugins/load_tester/load_tester_config.c

@@ -150,7 +150,7 @@ struct private_load_tester_config_t {
 	/**
 	 * incremental numbering of generated configs
 	 */
-	u_int num;
+	refcount_t num;
 
 	/**
 	 * Dynamic source port, if used
@@ -802,7 +802,7 @@ METHOD(backend_t, get_peer_cfg_by_name, peer_cfg_t*,
 {
 	if (streq(name, "load-test"))
 	{
-		return generate_config(this, this->num++);
+		return generate_config(this, (u_int)ref_get(&this->num));
 	}
 	return NULL;
 }

src/libcharon/plugins/load_tester/load_tester_ipsec.c

@@ -31,14 +31,14 @@ struct private_load_tester_ipsec_t {
 	/**
 	 * faked SPI counter
 	 */
-	u_int32_t spi;
+	refcount_t spi;
 };
 
 METHOD(kernel_ipsec_t, get_spi, status_t,
 	private_load_tester_ipsec_t *this, host_t *src, host_t *dst,
 	u_int8_t protocol, u_int32_t reqid, u_int32_t *spi)
 {
-	*spi = ++this->spi;
+	*spi = (uint32_t)ref_get(&this->spi);
 	return SUCCESS;
 }
 

src/libcharon/sa/ike_sa_manager.c

@@ -353,6 +353,11 @@ struct private_ike_sa_manager_t {
 	 */
 	shareable_segment_t *half_open_segments;
 
+	/**
+	 * Total number of half-open IKE_SAs.
+	 */
+	refcount_t half_open_count;
+
 	/**
 	 * Hash table with connected_peers_t objects.
 	 */
@@ -764,6 +769,7 @@ static void put_half_open(private_ike_sa_manager_t *this, entry_t *entry)
 		this->half_open_table[row] = item;
 	}
 	this->half_open_segments[segment].count++;
+	ref_get(&this->half_open_count);
 	lock->unlock(lock);
 }
 
@@ -803,6 +809,7 @@ static void remove_half_open(private_ike_sa_manager_t *this, entry_t *entry)
 				free(item);
 			}
 			this->half_open_segments[segment].count--;
+			ignore_result(ref_put(&this->half_open_count));
 			break;
 		}
 		prev = item;
@@ -1962,13 +1969,7 @@ METHOD(ike_sa_manager_t, get_half_open_count, u_int,
 	}
 	else
 	{
-		for (segment = 0; segment < this->segment_count; segment++)
-		{
-			lock = this->half_open_segments[segment].lock;
-			lock->read_lock(lock);
-			count += this->half_open_segments[segment].count;
-			lock->unlock(lock);
-		}
+		count = (u_int)ref_cur(&this->half_open_count);
 	}
 	return count;
 }

src/libstrongswan/utils/utils.c

@@ -511,7 +511,7 @@ void nop()
 {
 }
 
-#ifndef HAVE_GCC_ATOMIC_OPERATIONS
+#if !defined(HAVE_GCC_ATOMIC_OPERATIONS) && !defined(HAVE_GCC_SYNC_OPERATIONS)
 
 /**
  * We use a single mutex for all refcount variables.
@@ -528,7 +528,6 @@ refcount_t ref_get(refcount_t *ref)
 	pthread_mutex_lock(&ref_mutex);
 	current = ++(*ref);
 	pthread_mutex_unlock(&ref_mutex);
-
 	return current;
 }
 
@@ -545,6 +544,19 @@ bool ref_put(refcount_t *ref)
 	return !more_refs;
 }
 
+/**
+ * Current refcount
+ */
+refcount_t ref_cur(refcount_t *ref)
+{
+	refcount_t current;
+
+	pthread_mutex_lock(&ref_mutex);
+	current = *ref;
+	pthread_mutex_unlock(&ref_mutex);
+	return current;
+}
+
 /**
  * Single mutex for all compare and swap operations.
  */
@@ -566,7 +578,7 @@ bool cas_##name(type *ptr, type oldval, type newval) \
 _cas_impl(bool, bool)
 _cas_impl(ptr, void*)
 
-#endif /* HAVE_GCC_ATOMIC_OPERATIONS */
+#endif /* !HAVE_GCC_ATOMIC_OPERATIONS && !HAVE_GCC_SYNC_OPERATIONS */
 
 
 #ifdef HAVE_FMEMOPEN_FALLBACK

src/libstrongswan/utils/utils.h

@@ -750,20 +750,40 @@ typedef u_int refcount_t;
 
 #ifdef HAVE_GCC_ATOMIC_OPERATIONS
 
+#define ref_get(ref) __atomic_add_fetch(ref, 1, __ATOMIC_RELAXED)
+/* The relaxed memory model works fine for increments as these (usually) don't
+ * change the state of refcounted objects.  But here we have to ensure that we
+ * free the right stuff if ref counted objects are mutable.  So we have to sync
+ * with other threads that call ref_put().  It would be sufficient to use
+ * __ATOMIC_RELEASE here and then call __atomic_thread_fence() with
+ * __ATOMIC_ACQUIRE if we reach 0, but since we don't have control over the use
+ * of ref_put() we have to make sure. */
+#define ref_put(ref) (!__atomic_sub_fetch(ref, 1, __ATOMIC_ACQ_REL))
+#define ref_cur(ref) __atomic_load_n(ref, __ATOMIC_RELAXED)
+
+#define _cas_impl(ptr, oldval, newval) ({ typeof(oldval) _old = oldval; \
+			__atomic_compare_exchange_n(ptr, &_old, newval, FALSE, \
+										__ATOMIC_SEQ_CST, __ATOMIC_RELAXED); })
+#define cas_bool(ptr, oldval, newval) _cas_impl(ptr, oldval, newval)
+#define cas_ptr(ptr, oldval, newval) _cas_impl(ptr, oldval, newval)
+
+#elif defined(HAVE_GCC_SYNC_OPERATIONS)
+
 #define ref_get(ref) __sync_add_and_fetch(ref, 1)
 #define ref_put(ref) (!__sync_sub_and_fetch(ref, 1))
+#define ref_cur(ref) __sync_fetch_and_add(ref, 0)
 
 #define cas_bool(ptr, oldval, newval) \
 					(__sync_bool_compare_and_swap(ptr, oldval, newval))
 #define cas_ptr(ptr, oldval, newval) \
 					(__sync_bool_compare_and_swap(ptr, oldval, newval))
 
-#else /* !HAVE_GCC_ATOMIC_OPERATIONS */
+#else /* !HAVE_GCC_ATOMIC_OPERATIONS && !HAVE_GCC_SYNC_OPERATIONS */
 
 /**
  * Get a new reference.
  *
- * Increments the reference counter atomic.
+ * Increments the reference counter atomically.
  *
  * @param ref	pointer to ref counter
  * @return		new value of ref
@@ -773,7 +793,7 @@ refcount_t ref_get(refcount_t *ref);
 /**
  * Put back a unused reference.
  *
- * Decrements the reference counter atomic and
+ * Decrements the reference counter atomically and
  * says if more references available.
  *
  * @param ref	pointer to ref counter
@@ -781,6 +801,14 @@ refcount_t ref_get(refcount_t *ref);
  */
 bool ref_put(refcount_t *ref);
 
+/**
+ * Get the current value of the reference counter.
+ *
+ * @param ref	pointer to ref counter
+ * @return		current value of ref
+ */
+refcount_t ref_cur(refcount_t *ref);
+
 /**
  * Atomically replace value of ptr with newval if it currently equals oldval.
  *