Thomas, The latest btrfs code uses rwsem_is_contended() in the function caching_thread(). On RT systems, include/linux/rwsem.h is replaced with include/linux/rwsem_rt.h which does not provide a definition for rwsem_is_contended(). This commit provides a definition that should work on RT (where the lock is actually an rt_mutex).
Signed-off-by: Clark Williams <willi...@redhat.com>
---
include/linux/rwsem_rt.h | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/include/linux/rwsem_rt.h b/include/linux/rwsem_rt.h
index e94d945c5844..77035d7abc04 100644
--- a/include/linux/rwsem_rt.h
+++ b/include/linux/rwsem_rt.h
@@ -125,4 +125,9 @@ static inline void down_write_nest_lock(struct rw_semaphore
*sem,
rt_down_write_nested_lock(sem, NULL);
}
#endif
+
+static inline int rwsem_is_contended(struct rw_semaphore *sem)
+{
+ return !plist_head_empty(&sem->lock.wait_list);
+}
#endif
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