Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull RCU and LKMM changes from Paul E. McKenney:

  - Documentation updates.

  - Miscellaneous fixes.

  - Dynamic tick (nohz) updates, perhaps most notably changes to
    force the tick on when needed due to lengthy in-kernel execution
    on CPUs on which RCU is waiting.

  - Replace rcu_swap_protected() with rcu_prepace_pointer().

  - Torture-test updates.

  - Linux-kernel memory consistency model updates.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

7 files changed, 54 insertions, 51 deletions

diff --git a/include/linux/rculist_bl.h b/include/linux/rculist_bl.h
index 66e73ec1aa99..0b952d06eb0b 100644
--- a/include/linux/rculist_bl.h
+++ b/include/linux/rculist_bl.h
@@ -25,34 +25,6 @@ static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
 }
 
 /**
- * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
- * @n: the element to delete from the hash list.
- *
- * Note: hlist_bl_unhashed() on the node returns true after this. It is
- * useful for RCU based read lockfree traversal if the writer side
- * must know if the list entry is still hashed or already unhashed.
- *
- * In particular, it means that we can not poison the forward pointers
- * that may still be used for walking the hash list and we can only
- * zero the pprev pointer so list_unhashed() will return true after
- * this.
- *
- * The caller must take whatever precautions are necessary (such as
- * holding appropriate locks) to avoid racing with another
- * list-mutation primitive, such as hlist_bl_add_head_rcu() or
- * hlist_bl_del_rcu(), running on this same list.  However, it is
- * perfectly legal to run concurrently with the _rcu list-traversal
- * primitives, such as hlist_bl_for_each_entry_rcu().
- */
-static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n)
-{
-	if (!hlist_bl_unhashed(n)) {
-		__hlist_bl_del(n);
-		n->pprev = NULL;
-	}
-}
-
-/**
  * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
  * @n: the element to delete from the hash list.
  *
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 75a2eded7aa2..185dd9736863 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -383,6 +383,24 @@ do {									      \
 } while (0)
 
 /**
+ * rcu_replace_pointer() - replace an RCU pointer, returning its old value
+ * @rcu_ptr: RCU pointer, whose old value is returned
+ * @ptr: regular pointer
+ * @c: the lockdep conditions under which the dereference will take place
+ *
+ * Perform a replacement, where @rcu_ptr is an RCU-annotated
+ * pointer and @c is the lockdep argument that is passed to the
+ * rcu_dereference_protected() call used to read that pointer.  The old
+ * value of @rcu_ptr is returned, and @rcu_ptr is set to @ptr.
+ */
+#define rcu_replace_pointer(rcu_ptr, ptr, c)				\
+({									\
+	typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c));	\
+	rcu_assign_pointer((rcu_ptr), (ptr));				\
+	__tmp;								\
+})
+
+/**
  * rcu_swap_protected() - swap an RCU and a regular pointer
  * @rcu_ptr: RCU pointer
  * @ptr: regular pointer
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 9bf1dfe7781f..37b6f0c2b79d 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -84,6 +84,7 @@ static inline void rcu_scheduler_starting(void) { }
 #endif /* #else #ifndef CONFIG_SRCU */
 static inline void rcu_end_inkernel_boot(void) { }
 static inline bool rcu_is_watching(void) { return true; }
+static inline void rcu_momentary_dyntick_idle(void) { }
 
 /* Avoid RCU read-side critical sections leaking across. */
 static inline void rcu_all_qs(void) { barrier(); }
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 18b1ed9864b0..c5147de885ec 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -37,6 +37,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func);
 
 void rcu_barrier(void);
 bool rcu_eqs_special_set(int cpu);
+void rcu_momentary_dyntick_idle(void);
 unsigned long get_state_synchronize_rcu(void);
 void cond_synchronize_rcu(unsigned long oldstate);
 
diff --git a/include/linux/tick.h b/include/linux/tick.h
index f92a10b5e112..39eb44564058 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -108,7 +108,8 @@ enum tick_dep_bits {
 	TICK_DEP_BIT_POSIX_TIMER	= 0,
 	TICK_DEP_BIT_PERF_EVENTS	= 1,
 	TICK_DEP_BIT_SCHED		= 2,
-	TICK_DEP_BIT_CLOCK_UNSTABLE	= 3
+	TICK_DEP_BIT_CLOCK_UNSTABLE	= 3,
+	TICK_DEP_BIT_RCU		= 4
 };
 
 #define TICK_DEP_MASK_NONE		0
@@ -116,6 +117,7 @@ enum tick_dep_bits {
 #define TICK_DEP_MASK_PERF_EVENTS	(1 << TICK_DEP_BIT_PERF_EVENTS)
 #define TICK_DEP_MASK_SCHED		(1 << TICK_DEP_BIT_SCHED)
 #define TICK_DEP_MASK_CLOCK_UNSTABLE	(1 << TICK_DEP_BIT_CLOCK_UNSTABLE)
+#define TICK_DEP_MASK_RCU		(1 << TICK_DEP_BIT_RCU)
 
 #ifdef CONFIG_NO_HZ_COMMON
 extern bool tick_nohz_enabled;
@@ -268,6 +270,9 @@ static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
 static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
 
+static inline void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) { }
+static inline void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { }
+
 static inline void tick_dep_set(enum tick_dep_bits bit) { }
 static inline void tick_dep_clear(enum tick_dep_bits bit) { }
 static inline void tick_dep_set_cpu(int cpu, enum tick_dep_bits bit) { }
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 694bd040cf51..66122602bd08 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -93,16 +93,16 @@ TRACE_EVENT_RCU(rcu_grace_period,
  * the data from the rcu_node structure, other than rcuname, which comes
  * from the rcu_state structure, and event, which is one of the following:
  *
- * "Startleaf": Request a grace period based on leaf-node data.
+ * "Cleanup": Clean up rcu_node structure after previous GP.
+ * "CleanupMore": Clean up, and another GP is needed.
+ * "EndWait": Complete wait.
+ * "NoGPkthread": The RCU grace-period kthread has not yet started.
  * "Prestarted": Someone beat us to the request
  * "Startedleaf": Leaf node marked for future GP.
  * "Startedleafroot": All nodes from leaf to root marked for future GP.
  * "Startedroot": Requested a nocb grace period based on root-node data.
- * "NoGPkthread": The RCU grace-period kthread has not yet started.
+ * "Startleaf": Request a grace period based on leaf-node data.
  * "StartWait": Start waiting for the requested grace period.
- * "EndWait": Complete wait.
- * "Cleanup": Clean up rcu_node structure after previous GP.
- * "CleanupMore": Clean up, and another GP is needed.
  */
 TRACE_EVENT_RCU(rcu_future_grace_period,
 
@@ -258,20 +258,27 @@ TRACE_EVENT_RCU(rcu_exp_funnel_lock,
  * the number of the offloaded CPU are extracted.  The third and final
  * argument is a string as follows:
  *
- *	"WakeEmpty": Wake rcuo kthread, first CB to empty list.
- *	"WakeEmptyIsDeferred": Wake rcuo kthread later, first CB to empty list.
- *	"WakeOvf": Wake rcuo kthread, CB list is huge.
- *	"WakeOvfIsDeferred": Wake rcuo kthread later, CB list is huge.
- *	"WakeNot": Don't wake rcuo kthread.
- *	"WakeNotPoll": Don't wake rcuo kthread because it is polling.
- *	"DeferredWake": Carried out the "IsDeferred" wakeup.
- *	"Poll": Start of new polling cycle for rcu_nocb_poll.
- *	"Sleep": Sleep waiting for GP for !rcu_nocb_poll.
- *	"CBSleep": Sleep waiting for CBs for !rcu_nocb_poll.
- *	"WokeEmpty": rcuo kthread woke to find empty list.
- *	"WokeNonEmpty": rcuo kthread woke to find non-empty list.
- *	"WaitQueue": Enqueue partially done, timed wait for it to complete.
- *	"WokeQueue": Partial enqueue now complete.
+ * "AlreadyAwake": The to-be-awakened rcuo kthread is already awake.
+ * "Bypass": rcuo GP kthread sees non-empty ->nocb_bypass.
+ * "CBSleep": rcuo CB kthread sleeping waiting for CBs.
+ * "Check": rcuo GP kthread checking specified CPU for work.
+ * "DeferredWake": Timer expired or polled check, time to wake.
+ * "DoWake": The to-be-awakened rcuo kthread needs to be awakened.
+ * "EndSleep": Done waiting for GP for !rcu_nocb_poll.
+ * "FirstBQ": New CB to empty ->nocb_bypass (->cblist maybe non-empty).
+ * "FirstBQnoWake": FirstBQ plus rcuo kthread need not be awakened.
+ * "FirstBQwake": FirstBQ plus rcuo kthread must be awakened.
+ * "FirstQ": New CB to empty ->cblist (->nocb_bypass maybe non-empty).
+ * "NeedWaitGP": rcuo GP kthread must wait on a grace period.
+ * "Poll": Start of new polling cycle for rcu_nocb_poll.
+ * "Sleep": Sleep waiting for GP for !rcu_nocb_poll.
+ * "Timer": Deferred-wake timer expired.
+ * "WakeEmptyIsDeferred": Wake rcuo kthread later, first CB to empty list.
+ * "WakeEmpty": Wake rcuo kthread, first CB to empty list.
+ * "WakeNot": Don't wake rcuo kthread.
+ * "WakeNotPoll": Don't wake rcuo kthread because it is polling.
+ * "WakeOvfIsDeferred": Wake rcuo kthread later, CB list is huge.
+ * "WokeEmpty": rcuo CB kthread woke to find empty list.
  */
 TRACE_EVENT_RCU(rcu_nocb_wake,
 
@@ -713,8 +720,6 @@ TRACE_EVENT_RCU(rcu_torture_read,
  *	"Begin": rcu_barrier() started.
  *	"EarlyExit": rcu_barrier() piggybacked, thus early exit.
  *	"Inc1": rcu_barrier() piggyback check counter incremented.
- *	"OfflineNoCB": rcu_barrier() found callback on never-online CPU
- *	"OnlineNoCB": rcu_barrier() found online no-CBs CPU.
  *	"OnlineQ": rcu_barrier() found online CPU with callbacks.
  *	"OnlineNQ": rcu_barrier() found online CPU, no callbacks.
  *	"IRQ": An rcu_barrier_callback() callback posted on remote CPU.
diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index b7a904825e7d..295517f109d7 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -367,7 +367,8 @@ TRACE_EVENT(itimer_expire,
 		tick_dep_name(POSIX_TIMER)		\
 		tick_dep_name(PERF_EVENTS)		\
 		tick_dep_name(SCHED)			\
-		tick_dep_name_end(CLOCK_UNSTABLE)
+		tick_dep_name(CLOCK_UNSTABLE)		\
+		tick_dep_name_end(RCU)
 
 #undef tick_dep_name
 #undef tick_dep_mask_name