[PATCH] Deprecate synchronize_kernel, GPL replacement
The synchronize_kernel() primitive is used for quite a few different purposes:
waiting for RCU readers, waiting for NMIs, waiting for interrupts, and so on.
This makes RCU code harder to read, since synchronize_kernel() might or might
not have matching rcu_read_lock()s. This patch creates a new
synchronize_rcu() that is to be used for RCU readers and a new
synchronize_sched() that is used for the rest. These two new primitives
currently have the same implementation, but this is might well change with
additional real-time support. Both new primitives are GPL-only, the old
primitive is deprecated.
Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index ad49772..f436993 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -444,15 +444,18 @@
}
/**
- * synchronize_kernel - wait until a grace period has elapsed.
+ * synchronize_rcu - wait until a grace period has elapsed.
*
* Control will return to the caller some time after a full grace
* period has elapsed, in other words after all currently executing RCU
* read-side critical sections have completed. RCU read-side critical
* sections are delimited by rcu_read_lock() and rcu_read_unlock(),
* and may be nested.
+ *
+ * If your read-side code is not protected by rcu_read_lock(), do -not-
+ * use synchronize_rcu().
*/
-void synchronize_kernel(void)
+void synchronize_rcu(void)
{
struct rcu_synchronize rcu;
@@ -464,7 +467,16 @@
wait_for_completion(&rcu.completion);
}
+/*
+ * Deprecated, use synchronize_rcu() or synchronize_sched() instead.
+ */
+void synchronize_kernel(void)
+{
+ synchronize_rcu();
+}
+
module_param(maxbatch, int, 0);
EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */
EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL_GPL(synchronize_rcu);
EXPORT_SYMBOL(synchronize_kernel); /* WARNING: GPL-only in April 2006. */