Merge 'Linux v3.0' into Litmus

Some notes:
* Litmus^RT scheduling class is the topmost scheduling class
  (above stop_sched_class).
* scheduler_ipi() function (e.g., in smp_reschedule_interrupt())
  may increase IPI latencies.
* Added path into schedule() to quickly re-evaluate scheduling
  decision without becoming preemptive again. This used to be
  a standard path before the removal of BKL.

Conflicts:
	Makefile
	arch/arm/kernel/calls.S
	arch/arm/kernel/smp.c
	arch/x86/include/asm/unistd_32.h
	arch/x86/kernel/smp.c
	arch/x86/kernel/syscall_table_32.S
	include/linux/hrtimer.h
	kernel/printk.c
	kernel/sched.c
	kernel/sched_fair.c

1 files changed, 27 insertions, 9 deletions

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 4d169835fb36..7784bd216b6a 100644
--- 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);
 
@@ -140,10 +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();
@@ -182,10 +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();
@@ -212,14 +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.
+                 * 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(1);
+                WARN_ON_ONCE(1);
                 return 0;
-#else
+#endif
                 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
                     irqs_disabled()) {
-                        WARN_ON(1);
+                        WARN_ON_ONCE(1);
                         return 0;
                 }
                 rcu_barrier();
@@ -227,7 +246,6 @@ 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;
         }