Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (78 commits)
  Revert "rcu: Decrease memory-barrier usage based on semi-formal proof"
  net,rcu: convert call_rcu(prl_entry_destroy_rcu) to kfree
  batman,rcu: convert call_rcu(softif_neigh_free_rcu) to kfree_rcu
  batman,rcu: convert call_rcu(neigh_node_free_rcu) to kfree()
  batman,rcu: convert call_rcu(gw_node_free_rcu) to kfree_rcu
  net,rcu: convert call_rcu(kfree_tid_tx) to kfree_rcu()
  net,rcu: convert call_rcu(xt_osf_finger_free_rcu) to kfree_rcu()
  net/mac80211,rcu: convert call_rcu(work_free_rcu) to kfree_rcu()
  net,rcu: convert call_rcu(wq_free_rcu) to kfree_rcu()
  net,rcu: convert call_rcu(phonet_device_rcu_free) to kfree_rcu()
  perf,rcu: convert call_rcu(swevent_hlist_release_rcu) to kfree_rcu()
  perf,rcu: convert call_rcu(free_ctx) to kfree_rcu()
  net,rcu: convert call_rcu(__nf_ct_ext_free_rcu) to kfree_rcu()
  net,rcu: convert call_rcu(net_generic_release) to kfree_rcu()
  net,rcu: convert call_rcu(netlbl_unlhsh_free_addr6) to kfree_rcu()
  net,rcu: convert call_rcu(netlbl_unlhsh_free_addr4) to kfree_rcu()
  security,rcu: convert call_rcu(sel_netif_free) to kfree_rcu()
  net,rcu: convert call_rcu(xps_dev_maps_release) to kfree_rcu()
  net,rcu: convert call_rcu(xps_map_release) to kfree_rcu()
  net,rcu: convert call_rcu(rps_map_release) to kfree_rcu()
  ...

1 files changed, 24 insertions, 8 deletions

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index f3240e987928..7784bd216b6a 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -142,10 +142,17 @@ static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
                  * Ensure that queued callbacks are all executed.
                  * If we detect that we are nested in a RCU read-side critical
                  * section, we should simply fail, otherwise we would deadlock.
+                 * In !PREEMPT configurations, there is no way to tell if we are
+                 * in a RCU read-side critical section or not, so we never
+                 * attempt any fixup and just print a warning.
                  */
+#ifndef CONFIG_PREEMPT
+                WARN_ON_ONCE(1);
+                return 0;
+#endif
                 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
                     irqs_disabled()) {
-                        WARN_ON(1);
+                        WARN_ON_ONCE(1);
                         return 0;
                 }
                 rcu_barrier();
@@ -184,10 +191,17 @@ static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
                  * Ensure that queued callbacks are all executed.
                  * If we detect that we are nested in a RCU read-side critical
                  * section, we should simply fail, otherwise we would deadlock.
+                 * In !PREEMPT configurations, there is no way to tell if we are
+                 * in a RCU read-side critical section or not, so we never
+                 * attempt any fixup and just print a warning.
                  */
+#ifndef CONFIG_PREEMPT
+                WARN_ON_ONCE(1);
+                return 0;
+#endif
                 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
                     irqs_disabled()) {
-                        WARN_ON(1);
+                        WARN_ON_ONCE(1);
                         return 0;
                 }
                 rcu_barrier();
@@ -214,15 +228,17 @@ static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
                  * Ensure that queued callbacks are all executed.
                  * If we detect that we are nested in a RCU read-side critical
                  * section, we should simply fail, otherwise we would deadlock.
-                 * Note that the machinery to reliably determine whether
-                 * or not we are in an RCU read-side critical section
-                 * exists only in the preemptible RCU implementations
-                 * (TINY_PREEMPT_RCU and TREE_PREEMPT_RCU), which is why
-                 * DEBUG_OBJECTS_RCU_HEAD is disallowed if !PREEMPT.
+                 * In !PREEMPT configurations, there is no way to tell if we are
+                 * in a RCU read-side critical section or not, so we never
+                 * attempt any fixup and just print a warning.
                  */
+#ifndef CONFIG_PREEMPT
+                WARN_ON_ONCE(1);
+                return 0;
+#endif
                 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
                     irqs_disabled()) {
-                        WARN_ON(1);
+                        WARN_ON_ONCE(1);
                         return 0;
                 }
                 rcu_barrier();