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

Pull RCU updates from Ingo Molnar:
 "The main changes in this cycle were:

   - 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.

   - Linux-kernel memory consistency model updates.

   - Replace rcu_swap_protected() with rcu_prepace_pointer().

   - Torture-test updates.

   - Documentation updates.

   - Miscellaneous fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (51 commits)
  security/safesetid: Replace rcu_swap_protected() with rcu_replace_pointer()
  net/sched: Replace rcu_swap_protected() with rcu_replace_pointer()
  net/netfilter: Replace rcu_swap_protected() with rcu_replace_pointer()
  net/core: Replace rcu_swap_protected() with rcu_replace_pointer()
  bpf/cgroup: Replace rcu_swap_protected() with rcu_replace_pointer()
  fs/afs: Replace rcu_swap_protected() with rcu_replace_pointer()
  drivers/scsi: Replace rcu_swap_protected() with rcu_replace_pointer()
  drm/i915: Replace rcu_swap_protected() with rcu_replace_pointer()
  x86/kvm/pmu: Replace rcu_swap_protected() with rcu_replace_pointer()
  rcu: Upgrade rcu_swap_protected() to rcu_replace_pointer()
  rcu: Suppress levelspread uninitialized messages
  rcu: Fix uninitialized variable in nocb_gp_wait()
  rcu: Update descriptions for rcu_future_grace_period tracepoint
  rcu: Update descriptions for rcu_nocb_wake tracepoint
  rcu: Remove obsolete descriptions for rcu_barrier tracepoint
  rcu: Ensure that ->rcu_urgent_qs is set before resched IPI
  workqueue: Convert for_each_wq to use built-in list check
  rcu: Several rcu_segcblist functions can be static
  rcu: Remove unused function hlist_bl_del_init_rcu()
  Documentation: Rename rcu_node_context_switch() to rcu_note_context_switch()
  ...

5 files changed, 26 insertions, 29 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 7e050a356cc5..7896f792d3b0 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) { }