[PATCH] add rcu_barrier() synchronization point
This introduces a new interface - rcu_barrier() which waits until all
the RCUs queued until this call have been completed.
Reiser4 needs this, because we do more than just freeing memory object
in our RCU callback: we also remove it from the list hanging off
super-block. This means, that before freeing reiser4-specific portion
of super-block (during umount) we have to wait until all pending RCU
callbacks are executed.
The only change of reiser4 made to the original patch, is exporting of
rcu_barrier().
Cc: Hans Reiser <reiser@namesys.com>
Cc: Vladimir V. Saveliev <vs@namesys.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index cce2559..a471f3b 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -100,6 +100,7 @@
struct rcu_head *donelist;
struct rcu_head **donetail;
int cpu;
+ struct rcu_head barrier;
};
DECLARE_PER_CPU(struct rcu_data, rcu_data);
@@ -285,6 +286,7 @@
extern __deprecated_for_modules void synchronize_kernel(void);
extern void synchronize_rcu(void);
void synchronize_idle(void);
+extern void rcu_barrier(void);
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPDATE_H */