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 are:

   - Debloat RCU headers

   - Parallelize SRCU callback handling (plus overlapping patches)

   - Improve the performance of Tree SRCU on a CPU-hotplug stress test

   - Documentation updates

   - Miscellaneous fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (74 commits)
  rcu: Open-code the rcu_cblist_n_lazy_cbs() function
  rcu: Open-code the rcu_cblist_n_cbs() function
  rcu: Open-code the rcu_cblist_empty() function
  rcu: Separately compile large rcu_segcblist functions
  srcu: Debloat the <linux/rcu_segcblist.h> header
  srcu: Adjust default auto-expediting holdoff
  srcu: Specify auto-expedite holdoff time
  srcu: Expedite first synchronize_srcu() when idle
  srcu: Expedited grace periods with reduced memory contention
  srcu: Make rcutorture writer stalls print SRCU GP state
  srcu: Exact tracking of srcu_data structures containing callbacks
  srcu: Make SRCU be built by default
  srcu: Fix Kconfig botch when SRCU not selected
  rcu: Make non-preemptive schedule be Tasks RCU quiescent state
  srcu: Expedite srcu_schedule_cbs_snp() callback invocation
  srcu: Parallelize callback handling
  kvm: Move srcu_struct fields to end of struct kvm
  rcu: Fix typo in PER_RCU_NODE_PERIOD header comment
  rcu: Use true/false in assignment to bool
  rcu: Use bool value directly
  ...

1 files changed, 18 insertions, 14 deletions

diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 5cbd8b2395b8..8ed6c9f6133c 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -562,7 +562,9 @@ This section presents a "toy" RCU implementation that is based on
 familiar locking primitives.  Its overhead makes it a non-starter for
 real-life use, as does its lack of scalability.  It is also unsuitable
 for realtime use, since it allows scheduling latency to "bleed" from
-one read-side critical section to another.
+one read-side critical section to another.  It also assumes recursive
+reader-writer locks:  If you try this with non-recursive locks, and
+you allow nested rcu_read_lock() calls, you can deadlock.
 
 However, it is probably the easiest implementation to relate to, so is
 a good starting point.
@@ -587,20 +589,21 @@ It is extremely simple:
 		write_unlock(&rcu_gp_mutex);
 	}
 
-[You can ignore rcu_assign_pointer() and rcu_dereference() without
-missing much.  But here they are anyway.  And whatever you do, don't
-forget about them when submitting patches making use of RCU!]
+[You can ignore rcu_assign_pointer() and rcu_dereference() without missing
+much.  But here are simplified versions anyway.  And whatever you do,
+don't forget about them when submitting patches making use of RCU!]
 
-	#define rcu_assign_pointer(p, v)	({ \
-							smp_wmb(); \
-							(p) = (v); \
-						})
+	#define rcu_assign_pointer(p, v) \
+	({ \
+		smp_store_release(&(p), (v)); \
+	})
 
-	#define rcu_dereference(p)     ({ \
-					typeof(p) _________p1 = p; \
-					smp_read_barrier_depends(); \
-					(_________p1); \
-					})
+	#define rcu_dereference(p) \
+	({ \
+		typeof(p) _________p1 = p; \
+		smp_read_barrier_depends(); \
+		(_________p1); \
+	})
 
 
 The rcu_read_lock() and rcu_read_unlock() primitive read-acquire
@@ -925,7 +928,8 @@ d.	Do you need RCU grace periods to complete even in the face
 
 e.	Is your workload too update-intensive for normal use of
 	RCU, but inappropriate for other synchronization mechanisms?
-	If so, consider SLAB_DESTROY_BY_RCU.  But please be careful!
+	If so, consider SLAB_TYPESAFE_BY_RCU (which was originally
+	named SLAB_DESTROY_BY_RCU).  But please be careful!
 
 f.	Do you need read-side critical sections that are respected
 	even though they are in the middle of the idle loop, during