From efd0fe21e44f0f757b3cd80cdbaddb8423eeb410 Mon Sep 17 00:00:00 2001
From: Martin Willi <martin@strongswan.org>
Date: Tue, 2 Dec 2008 12:14:32 +0000
Subject: [PATCH] ref_get()/ref_put() use atomic gcc operations if supported,
 thanks to Thomas Jarosch for the patch

---
 configure.in              | 15 +++++++++++++++
 src/libstrongswan/utils.c | 20 +++++++-------------
 src/libstrongswan/utils.h | 10 ++++++++++
 3 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/configure.in b/configure.in
index a251c99125..ea9b6dd203 100644
--- a/configure.in
+++ b/configure.in
@@ -708,6 +708,21 @@ AC_HAVE_LIBRARY(dl)
 AC_CHECK_FUNCS(backtrace)
 AC_CHECK_FUNCS(dladdr)
 
+AC_MSG_CHECKING([for gcc atomic operations])
+AC_TRY_RUN(
+[
+	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);
+		return ref;
+	}
+],
+[AC_MSG_RESULT([yes]); AC_DEFINE(HAVE_GCC_ATOMIC_OPERATIONS)],
+[AC_MSG_RESULT([no])])
+
 if test x$gmp = xtrue; then
 	AC_HAVE_LIBRARY([gmp],[LIBS="$LIBS"],[AC_MSG_ERROR([GNU Multi Precision library gmp not found])])
 	AC_MSG_CHECKING([gmp.h version >= 4.1.4])
diff --git a/src/libstrongswan/utils.c b/src/libstrongswan/utils.c
index 942f2ade04..aa50b86b4f 100644
--- a/src/libstrongswan/utils.c
+++ b/src/libstrongswan/utils.c
@@ -20,7 +20,6 @@
 
 #include <sys/stat.h>
 #include <string.h>
-#include <pthread.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <dirent.h>
@@ -138,19 +137,16 @@ void nop()
 {
 }
 
+#ifndef HAVE_GCC_ATOMIC_OPERATIONS
+#include <pthread.h>
+
 /**
- * We use a single mutex for all refcount variables. This
- * is not optimal for performance, but the critical section
- * is not that long...
- * TODO: Consider to include a mutex in each refcount_t variable.
+ * We use a single mutex for all refcount variables. 
  */
 static pthread_mutex_t ref_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /**
- * Described in header.
- * 
- * TODO: May be implemented with atomic CPU instructions
- * instead of a mutex.
+ * Increase refcount
  */
 void ref_get(refcount_t *ref)
 {
@@ -160,10 +156,7 @@ void ref_get(refcount_t *ref)
 }
 
 /**
- * Described in header.
- * 
- * TODO: May be implemented with atomic CPU instructions
- * instead of a mutex.
+ * Decrease refcount
  */
 bool ref_put(refcount_t *ref)
 {
@@ -174,6 +167,7 @@ bool ref_put(refcount_t *ref)
 	pthread_mutex_unlock(&ref_mutex);
 	return !more_refs;
 }
+#endif /* HAVE_GCC_ATOMIC_OPERATIONS */
 
 /**
  * output handler in printf() for time_t
diff --git a/src/libstrongswan/utils.h b/src/libstrongswan/utils.h
index af619ea4b7..298253fdd4 100644
--- a/src/libstrongswan/utils.h
+++ b/src/libstrongswan/utils.h
@@ -248,6 +248,14 @@ void nop();
  */
 typedef volatile u_int refcount_t;
 
+
+#ifdef HAVE_GCC_ATOMIC_OPERATIONS
+
+#define ref_get(ref) {__sync_fetch_and_add(ref, 1); }
+#define ref_put(ref) (!__sync_sub_and_fetch(ref, 1))
+
+#else /* !HAVE_GCC_ATOMIC_OPERATIONS */
+
 /**
  * Get a new reference.
  *
@@ -268,6 +276,8 @@ void ref_get(refcount_t *ref);
  */
 bool ref_put(refcount_t *ref);
 
+#endif /* HAVE_GCC_ATOMIC_OPERATIONS */
+
 /**
  * Get printf hooks for time.
  *
-- 
2.47.2