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

Pull RCU updates from Ingo Molnar:
 "This cycle's RCU changes were:

   - A few more RCU flavor consolidation cleanups.

   - Updates to RCU's list-traversal macros improving lockdep usability.

   - Forward-progress improvements for no-CBs CPUs: Avoid ignoring
     incoming callbacks during grace-period waits.

   - Forward-progress improvements for no-CBs CPUs: Use ->cblist
     structure to take advantage of others' grace periods.

   - Also added a small commit that avoids needlessly inflicting
     scheduler-clock ticks on callback-offloaded CPUs.

   - Forward-progress improvements for no-CBs CPUs: Reduce contention on
     ->nocb_lock guarding ->cblist.

   - Forward-progress improvements for no-CBs CPUs: Add ->nocb_bypass
     list to further reduce contention on ->nocb_lock guarding ->cblist.

   - Miscellaneous fixes.

   - Torture-test updates.

   - minor LKMM updates"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (86 commits)
  MAINTAINERS: Update from paulmck@linux.ibm.com to paulmck@kernel.org
  rcu: Don't include <linux/ktime.h> in rcutiny.h
  rcu: Allow rcu_do_batch() to dynamically adjust batch sizes
  rcu/nocb: Don't wake no-CBs GP kthread if timer posted under overload
  rcu/nocb: Reduce __call_rcu_nocb_wake() leaf rcu_node ->lock contention
  rcu/nocb: Reduce nocb_cb_wait() leaf rcu_node ->lock contention
  rcu/nocb: Advance CBs after merge in rcutree_migrate_callbacks()
  rcu/nocb: Avoid synchronous wakeup in __call_rcu_nocb_wake()
  rcu/nocb: Print no-CBs diagnostics when rcutorture writer unduly delayed
  rcu/nocb: EXP Check use and usefulness of ->nocb_lock_contended
  rcu/nocb: Add bypass callback queueing
  rcu/nocb: Atomic ->len field in rcu_segcblist structure
  rcu/nocb: Unconditionally advance and wake for excessive CBs
  rcu/nocb: Reduce ->nocb_lock contention with separate ->nocb_gp_lock
  rcu/nocb: Reduce contention at no-CBs invocation-done time
  rcu/nocb: Reduce contention at no-CBs registry-time CB advancement
  rcu/nocb: Round down for number of no-CBs grace-period kthreads
  rcu/nocb: Avoid ->nocb_lock capture by corresponding CPU
  rcu/nocb: Avoid needless wakeups of no-CBs grace-period kthread
  rcu/nocb: Make __call_rcu_nocb_wake() safe for many callbacks
  ...

3 files changed, 23 insertions, 5 deletions

diff --git a/drivers/base/base.h b/drivers/base/base.h
index b405436ee28e..0d32544b6f91 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -165,6 +165,7 @@ static inline int devtmpfs_init(void) { return 0; }
 /* Device links support */
 extern int device_links_read_lock(void);
 extern void device_links_read_unlock(int idx);
+extern int device_links_read_lock_held(void);
 extern int device_links_check_suppliers(struct device *dev);
 extern void device_links_driver_bound(struct device *dev);
 extern void device_links_driver_cleanup(struct device *dev);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 1669d41fcddc..f0dd8e38fee3 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -68,6 +68,11 @@ void device_links_read_unlock(int idx)
 {
 	srcu_read_unlock(&device_links_srcu, idx);
 }
+
+int device_links_read_lock_held(void)
+{
+	return srcu_read_lock_held(&device_links_srcu);
+}
 #else /* !CONFIG_SRCU */
 static DECLARE_RWSEM(device_links_lock);
 
@@ -91,6 +96,13 @@ void device_links_read_unlock(int not_used)
 {
 	up_read(&device_links_lock);
 }
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+int device_links_read_lock_held(void)
+{
+	return lockdep_is_held(&device_links_lock);
+}
+#endif
 #endif /* !CONFIG_SRCU */
 
 /**
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index b75335508d2c..50def99df970 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -287,7 +287,8 @@ static int rpm_get_suppliers(struct device *dev)
 {
 	struct device_link *link;
 
-	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) {
+	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,
+				device_links_read_lock_held()) {
 		int retval;
 
 		if (!(link->flags & DL_FLAG_PM_RUNTIME) ||
@@ -309,7 +310,8 @@ static void rpm_put_suppliers(struct device *dev)
 {
 	struct device_link *link;
 
-	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) {
+	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,
+				device_links_read_lock_held()) {
 		if (READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND)
 			continue;
 
@@ -1640,7 +1642,8 @@ void pm_runtime_clean_up_links(struct device *dev)
 
 	idx = device_links_read_lock();
 
-	list_for_each_entry_rcu(link, &dev->links.consumers, s_node) {
+	list_for_each_entry_rcu(link, &dev->links.consumers, s_node,
+				device_links_read_lock_held()) {
 		if (link->flags & DL_FLAG_STATELESS)
 			continue;
 
@@ -1662,7 +1665,8 @@ void pm_runtime_get_suppliers(struct device *dev)
 
 	idx = device_links_read_lock();
 
-	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
+	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,
+				device_links_read_lock_held())
 		if (link->flags & DL_FLAG_PM_RUNTIME) {
 			link->supplier_preactivated = true;
 			refcount_inc(&link->rpm_active);
@@ -1683,7 +1687,8 @@ void pm_runtime_put_suppliers(struct device *dev)
 
 	idx = device_links_read_lock();
 
-	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
+	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,
+				device_links_read_lock_held())
 		if (link->supplier_preactivated) {
 			link->supplier_preactivated = false;
 			if (refcount_dec_not_one(&link->rpm_active))