From 8fa04e97a59178f3ed03056f7a8a318b0cc024c6 Mon Sep 17 00:00:00 2001
From: wangyb <wangyb>
Date: Thu, 4 Jun 2009 09:40:38 +0000
Subject: [PATCH] b=18015 a=adilger r=zhenyu.xu, sheng.yang

check if synchronize_rcu is available, otherwise use synchronize_kernel
---
 lustre/autoconf/lustre-core.m4         | 12 ++++++++++++
 lustre/include/linux/lustre_compat25.h |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/lustre/autoconf/lustre-core.m4 b/lustre/autoconf/lustre-core.m4
index cbf9877..7af19f5 100644
--- a/lustre/autoconf/lustre-core.m4
+++ b/lustre/autoconf/lustre-core.m4
@@ -809,6 +809,17 @@ LB_LINUX_TRY_COMPILE([
 ])
 ])
 
+# LC_EXPORT_SYNCHRONIZE_RCU
+# after 2.6.12 synchronize_rcu is preferred over synchronize_kernel
+AC_DEFUN([LC_EXPORT_SYNCHRONIZE_RCU],
+[LB_CHECK_SYMBOL_EXPORT([synchronize_rcu],
+[kernel/rcupdate.c],[
+        AC_DEFINE(HAVE_SYNCHRONIZE_RCU, 1,
+                [in 2.6.12 synchronize_rcu preferred over synchronize_kernel])
+],[
+])
+])
+
 # LC_INODE_I_MUTEX
 # after 2.6.15 inode have i_mutex intead of i_sem
 AC_DEFUN([LC_INODE_I_MUTEX],
@@ -1631,6 +1642,7 @@ AC_DEFUN([LC_PROG_LINUX],
 
          # 2.6.12
          LC_RW_TREE_LOCK
+         LC_EXPORT_SYNCHRONIZE_RCU
 
          # 2.6.15
          LC_INODE_I_MUTEX
diff --git a/lustre/include/linux/lustre_compat25.h b/lustre/include/linux/lustre_compat25.h
index 277b8ce..611e5be 100644
--- a/lustre/include/linux/lustre_compat25.h
+++ b/lustre/include/linux/lustre_compat25.h
@@ -607,6 +607,10 @@ static inline int ll_crypto_hmac(struct crypto_tfm *tfm,
 #define ll_crypto_tfm_alg_max_keysize	crypto_tfm_alg_max_keysize
 #endif /* HAVE_ASYNC_BLOCK_CIPHER */
 
+#ifndef HAVE_SYNCHRONIZE_RCU
+#define synchronize_rcu() synchronize_kernel()
+#endif
+
 #ifdef HAVE_SECURITY_PLUG
 #define ll_remove_suid(inode,mnt)               remove_suid(inode,mnt)
 #define ll_vfs_rmdir(dir,entry,mnt)             vfs_rmdir(dir,entry,mnt)
-- 
1.8.3.1