Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux...

[deliverable/linux.git] / kernel / rcupdate.c

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 4d169835fb362dcd6eb52a916a0d8e85e48c8fb8..f3240e987928ca9630b15d39784180339c8727dd 100644 (file)
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -73,12 +73,14 @@ int debug_lockdep_rcu_enabled(void)
 EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
 
 /**
- * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
+ * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
  *
  * Check for bottom half being disabled, which covers both the
  * CONFIG_PROVE_RCU and not cases.  Note that if someone uses
  * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
- * will show the situation.
+ * will show the situation.  This is useful for debug checks in functions
+ * that require that they be called within an RCU read-side critical
+ * section.
  *
  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
  */
@@ -86,7 +88,7 @@ int rcu_read_lock_bh_held(void)
 {
        if (!debug_lockdep_rcu_enabled())
                return 1;
-       return in_softirq();
+       return in_softirq() || irqs_disabled();
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
 
@@ -212,11 +214,12 @@ 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.
                 */
-#ifndef CONFIG_PREEMPT
-               WARN_ON(1);
-               return 0;
-#else
                if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
                    irqs_disabled()) {
                        WARN_ON(1);
@@ -227,7 +230,6 @@ static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
                rcu_barrier_bh();
                debug_object_free(head, &rcuhead_debug_descr);
                return 1;
-#endif
        default:
                return 0;
        }