Correctly handle rwsem_is_locked() behavior

[mirror_spl.git] / config / spl-build.m4

diff --git a/config/spl-build.m4 b/config/spl-build.m4
index facaf7404c73961bded44ca7db65ea16d07eb973..0b9f8f4301b1a2328d83e5a932f5ddfdaa00ab24 100644 (file)
--- a/config/spl-build.m4
+++ b/config/spl-build.m4
@@ -77,6 +77,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
        SPL_AC_5ARGS_PROC_HANDLER
        SPL_AC_KVASPRINTF
        SPL_AC_3ARGS_FILE_FSYNC
+       SPL_AC_EXPORTED_RWSEM_IS_LOCKED
 ])
 
 AC_DEFUN([SPL_AC_MODULE_SYMVERS], [
@@ -1598,3 +1599,19 @@ AC_DEFUN([SPL_AC_3ARGS_FILE_FSYNC], [
                AC_MSG_RESULT(no)
        ])
 ])
+
+dnl #
+dnl # 2.6.33 API change. Also backported in RHEL5 as of 2.6.18-190.el5.
+dnl # Earlier versions of rwsem_is_locked() were inline and had a race
+dnl # condition.  The fixed version is exported as a symbol.  The race
+dnl # condition is fixed by acquiring sem->wait_lock, so we must not
+dnl # call that version while holding sem->wait_lock.
+dnl #
+AC_DEFUN([SPL_AC_EXPORTED_RWSEM_IS_LOCKED], [
+       SPL_CHECK_SYMBOL_EXPORT(
+               [rwsem_is_locked],
+               [lib/rwsem-spinlock.c],
+               [AC_DEFINE(RWSEM_IS_LOCKED_TAKES_WAIT_LOCK, 1,
+               [rwsem_is_locked() acquires sem->wait_lock])],
+               [])
+])