[PATCH] Make RCU API inaccessible to non-GPL Linux kernel modules

Remove synchronize_kernel() (deprecated 2-APR-2005 in
http://lkml.org/lkml/2005/4/3/11) and makes the RCU API inaccessible to
non-GPL Linux kernel modules (as was announced more than one year ago in
http://lkml.org/lkml/2005/4/3/8).  Tested on x86 and ppc64.
Signed-off-by: N"Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Documentation/RCU/whatisRCU.txt

@@ -790,7 +790,6 @@ RCU pointer update:
 
 RCU grace period:
 
-	synchronize_kernel (deprecated)
 	synchronize_net
 	synchronize_sched
 	synchronize_rcu

Documentation/feature-removal-schedule.txt

@@ -33,21 +33,6 @@ Who:	Adrian Bunk <bunk@stusta.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>
-
----------------------------
-
 What:	raw1394: requests of type RAW1394_REQ_ISO_SEND, RAW1394_REQ_ISO_LISTEN
 When:	November 2006
 Why:	Deprecated in favour of the new ioctl-based rawiso interface, which is

include/linux/rcupdate.h

@@ -246,7 +246,7 @@ extern int rcu_needs_cpu(int cpu);
  * softirq handlers will have completed, since in some kernels, these
  * handlers can run in process context, and can block.
  *
- * This primitive provides the guarantees made by the (deprecated)
+ * This primitive provides the guarantees made by the (now removed)
  * synchronize_kernel() API.  In contrast, synchronize_rcu() only
  * guarantees that rcu_read_lock() sections will have completed.
  * In "classic RCU", these two guarantees happen to be one and
@@ -264,7 +264,6 @@ extern void FASTCALL(call_rcu(struct rcu_head *head,
 				void (*func)(struct rcu_head *head)));
 extern void FASTCALL(call_rcu_bh(struct rcu_head *head,
 				void (*func)(struct rcu_head *head)));
-extern __deprecated_for_modules void synchronize_kernel(void);
 extern void synchronize_rcu(void);
 void synchronize_idle(void);
 extern void rcu_barrier(void);

kernel/rcupdate.c

@@ -612,14 +612,6 @@ void synchronize_rcu(void)
 	wait_for_completion(&rcu.completion);
 }
 
-/*
- * Deprecated, use synchronize_rcu() or synchronize_sched() instead.
- */
-void synchronize_kernel(void)
-{
-	synchronize_rcu();
-}
-
 module_param(blimit, int, 0);
 module_param(qhimark, int, 0);
 module_param(qlowmark, int, 0);
@@ -627,7 +619,6 @@ module_param(qlowmark, int, 0);
 module_param(rsinterval, int, 0);
 #endif
 EXPORT_SYMBOL_GPL(rcu_batches_completed);
-EXPORT_SYMBOL_GPL_FUTURE(call_rcu);	/* WARNING: GPL-only in April 2006. */
-EXPORT_SYMBOL_GPL_FUTURE(call_rcu_bh);	/* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL_GPL(call_rcu);
+EXPORT_SYMBOL_GPL(call_rcu_bh);
 EXPORT_SYMBOL_GPL(synchronize_rcu);
-EXPORT_SYMBOL_GPL_FUTURE(synchronize_kernel); /* WARNING: GPL-only in April 2006. */