llist: Remove the platform-dependent NMI checks

Remove the nmi() checks spread around the code. in_nmi() is not available
on every architecture and it's a pretty obscure and ugly check in any case.

Cc: Huang Ying <ying.huang@intel.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1315461646-1379-3-git-send-email-ying.huang@intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/llist.h

@@ -35,8 +35,8 @@
  *
  * The basic atomic operation of this list is cmpxchg on long.  On
  * architectures that don't have NMI-safe cmpxchg implementation, the
- * list can NOT be used in NMI handler.  So code uses the list in NMI
- * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
+ * list can NOT be used in NMI handlers.  So code that uses the list in
+ * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
  *
  * Copyright 2010,2011 Intel Corp.
  *   Author: Huang Ying <ying.huang@intel.com>
@@ -147,10 +147,6 @@ static inline void llist_add(struct llist_node *new, struct llist_head *head)
 {
 	struct llist_node *entry, *old_entry;
 
-#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
-	BUG_ON(in_nmi());
-#endif
-
 	entry = head->first;
 	do {
 		old_entry = entry;
@@ -169,10 +165,6 @@ static inline void llist_add(struct llist_node *new, struct llist_head *head)
  */
 static inline struct llist_node *llist_del_all(struct llist_head *head)
 {
-#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
-	BUG_ON(in_nmi());
-#endif
-
 	return xchg(&head->first, NULL);
 }
 #endif /* LLIST_H */

lib/llist.c

@@ -3,8 +3,8 @@
  *
  * The basic atomic operation of this list is cmpxchg on long.  On
  * architectures that don't have NMI-safe cmpxchg implementation, the
- * list can NOT be used in NMI handler.  So code uses the list in NMI
- * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
+ * list can NOT be used in NMI handlers.  So code that uses the list in
+ * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
  *
  * Copyright 2010,2011 Intel Corp.
  *   Author: Huang Ying <ying.huang@intel.com>
@@ -40,10 +40,6 @@ void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
 {
 	struct llist_node *entry, *old_entry;
 
-#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
-	BUG_ON(in_nmi());
-#endif
-
 	entry = head->first;
 	do {
 		old_entry = entry;
@@ -71,10 +67,6 @@ struct llist_node *llist_del_first(struct llist_head *head)
 {
 	struct llist_node *entry, *old_entry, *next;
 
-#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
-	BUG_ON(in_nmi());
-#endif
-
 	entry = head->first;
 	do {
 		if (entry == NULL)