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 RCU subsystem changes in this cycle were:

  - Miscellaneous fixes, perhaps most notably removing obsolete code
    whose only purpose in life was to gather information for the
    now-removed RCU debugfs facility. Other notable changes include
    removing NO_HZ_FULL_ALL in favor of the nohz_full kernel boot
    parameter, minor optimizations for expedited grace periods, some
    added tracing, creating an RCU-specific workqueue using Tejun's new
    WQ_MEM_RECLAIM flag, and several cleanups to code and comments.

  - SRCU cleanups and optimizations.

  - Torture-test updates, perhaps most notably the adding of ARMv8
    support, but also including numerous cleanups and usability fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
  rcu: Create RCU-specific workqueues with rescuers
  torture: Provide more sensible nreader/nwriter defaults for rcuperf
  torture: Grace periods do not piggyback off of themselves
  torture: Adjust rcuperf trace processing to allow for workqueues
  torture: Default jitter off when running rcuperf
  torture: Specify qemu memory size with --memory argument
  rcutorture: Add basic ARM64 support to run scripts
  rcutorture: Update kvm.sh header comment
  rcutorture: Record which grace-period primitives are tested
  rcutorture: Re-enable testing of dynamic expediting
  rcutorture: Avoid fake-writer use of undefined primitives
  rcutorture: Abstract function and module names
  rcutorture: Replace multi-instance kzalloc() with kcalloc()
  rcu: Remove SRCU throttling
  srcu: Remove dead code in srcu_gp_end()
  srcu: Reduce scans of srcu_data in counter wrap check
  srcu: Prevent sdp->srcu_gp_seq_needed_exp counter wrap
  srcu: Abstract function name
  rcu: Make expedited RCU CPU selection avoid unnecessary stores
  rcu: Trace expedited GP delays due to transitioning CPUs
  ...

3 files changed, 11 insertions, 5 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 043d04784675..36360d07f25b 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -214,10 +214,12 @@ do { \
 #endif
 
 /*
- * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic
- * initialization and destruction of rcu_head on the stack. rcu_head structures
- * allocated dynamically in the heap or defined statically don't need any
- * initialization.
+ * The init_rcu_head_on_stack() and destroy_rcu_head_on_stack() calls
+ * are needed for dynamic initialization and destruction of rcu_head
+ * on the stack, and init_rcu_head()/destroy_rcu_head() are needed for
+ * dynamic initialization and destruction of statically allocated rcu_head
+ * structures.  However, rcu_head structures allocated dynamically in the
+ * heap don't need any initialization.
  */
 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
 void init_rcu_head(struct rcu_head *head);
diff --git a/include/linux/types.h b/include/linux/types.h
index c94d59ef96cc..ec13d02b3481 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -217,7 +217,7 @@ struct ustat {
  *
  * This guarantee is important for few reasons:
  *  - future call_rcu_lazy() will make use of lower bits in the pointer;
- *  - the structure shares storage spacer in struct page with @compound_head,
+ *  - the structure shares storage space in struct page with @compound_head,
  *    which encode PageTail() in bit 0. The guarantee is needed to avoid
  *    false-positive PageTail().
  */
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 0b50fda80db0..d8c33298c153 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -179,6 +179,10 @@ TRACE_EVENT(rcu_grace_period_init,
  *
  *	"snap": Captured snapshot of expedited grace period sequence number.
  *	"start": Started a real expedited grace period.
+ *	"reset": Started resetting the tree
+ *	"select": Started selecting the CPUs to wait on.
+ *	"selectofl": Selected CPU partially offline.
+ *	"startwait": Started waiting on selected CPUs.
  *	"end": Ended a real expedited grace period.
  *	"endwake": Woke piggybackers up.
  *	"done": Someone else did the expedited grace period for us.