[PATCH] kernel/rcupdate.c: make the exports EXPORT_SYMBOL_GPL

The gpl exports need to be put back.  Moving them to GPL -- but in a
measured manner, as I proposed on this list some months ago -- is fine.
Changing these particular exports precipitously is most definitely -not-
fine.  Here is my earlier proposal:

	http://marc.theaimsgroup.com/?l=linux-kernel&m=110520930301813&w=2

See below for a patch that puts the exports back, along with an updated
version of my earlier patch that starts the process of moving them to GPL.
I will also be following this message with RFC patches that introduce two
(EXPORT_SYMBOL_GPL) interfaces to replace synchronize_kernel(), which then
becomes deprecated.

Signed-off-by: <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/feature-removal-schedule.txt

@@ -48,3 +48,18 @@ When:	April 2005
 Why:	Replaced by ->compat_ioctl in file_operations and other method
 	vecors.
 Who:	Andi Kleen <ak@muc.de>, Christoph Hellwig <hch@lst.de>
+
+---------------------------
+
+What:	RCU API moves to EXPORT_SYMBOL_GPL
+When:	April 2006
+Files:	include/linux/rcupdate.h, kernel/rcupdate.c
+Why:	Outside of Linux, the only implementations of anything even
+	vaguely resembling RCU that I am aware of are in DYNIX/ptx,
+	VM/XA, Tornado, and K42.  I do not expect anyone to port binary
+	drivers or kernel modules from any of these, since the first two
+	are owned by IBM and the last two are open-source research OSes.
+	So these will move to GPL after a grace period to allow
+	people, who might be using implementations that I am not aware
+	of, to adjust to this upcoming change.
+Who:	Paul E. McKenney <paulmck@us.ibm.com>

kernel/rcupdate.c

@@ -465,6 +465,6 @@ void synchronize_kernel(void)
 }
 
 module_param(maxbatch, int, 0);
-EXPORT_SYMBOL_GPL(call_rcu);
-EXPORT_SYMBOL_GPL(call_rcu_bh);
-EXPORT_SYMBOL_GPL(synchronize_kernel);
+EXPORT_SYMBOL(call_rcu);  /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL(call_rcu_bh);  /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL(synchronize_kernel);  /* WARNING: GPL-only in April 2006. */