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 changes in this development cycle were:

   - Miscellaneous fixes, including a change to call_rcu()'s rcu_head
     alignment check.

   - Security-motivated list consistency checks, which are disabled by
     default behind DEBUG_LIST.

   - Torture-test updates.

   - Documentation updates, yet again just simple changes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  torture: Prevent jitter from delaying build-only runs
  torture: Remove obsolete files from rcutorture .gitignore
  rcu: Don't kick unless grace period or request
  rcu: Make expedited grace periods recheck dyntick idle state
  torture: Trace long read-side delays
  rcu: RCU_TRACE enables event tracing as well as debugfs
  rcu: Remove obsolete comment from __call_rcu()
  rcu: Remove obsolete rcu_check_callbacks() header comment
  rcu: Tighten up __call_rcu() rcu_head alignment check
  Documentation/RCU: Fix minor typo
  documentation: Present updated RCU guarantee
  bug: Avoid Kconfig warning for BUG_ON_DATA_CORRUPTION
  lib/Kconfig.debug: Fix typo in select statement
  lkdtm: Add tests for struct list corruption
  bug: Provide toggle for BUG on data corruption
  list: Split list_del() debug checking into separate function
  rculist: Consolidate DEBUG_LIST for list_add_rcu()
  list: Split list_add() debug checking into separate function

2 files changed, 25 insertions, 2 deletions

diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
index a4d3838130e4..39bcb74ea733 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.html
+++ b/Documentation/RCU/Design/Requirements/Requirements.html
@@ -547,7 +547,7 @@ The <tt>rcu_access_pointer()</tt> on line&nbsp;6 is similar to
 	It could reuse a value formerly fetched from this same pointer.
 	It could also fetch the pointer from <tt>gp</tt> in a byte-at-a-time
 	manner, resulting in <i>load tearing</i>, in turn resulting a bytewise
-	mash-up of two distince pointer values.
+	mash-up of two distinct pointer values.
 	It might even use value-speculation optimizations, where it makes
 	a wrong guess, but by the time it gets around to checking the
 	value, an update has changed the pointer to match the wrong guess.
@@ -659,6 +659,29 @@ systems with more than one CPU:
 	In other words, a given instance of <tt>synchronize_rcu()</tt>
 	can avoid waiting on a given RCU read-side critical section only
 	if it can prove that <tt>synchronize_rcu()</tt> started first.
+
+	<p>
+	A related question is &ldquo;When <tt>rcu_read_lock()</tt>
+	doesn't generate any code, why does it matter how it relates
+	to a grace period?&rdquo;
+	The answer is that it is not the relationship of
+	<tt>rcu_read_lock()</tt> itself that is important, but rather
+	the relationship of the code within the enclosed RCU read-side
+	critical section to the code preceding and following the
+	grace period.
+	If we take this viewpoint, then a given RCU read-side critical
+	section begins before a given grace period when some access
+	preceding the grace period observes the effect of some access
+	within the critical section, in which case none of the accesses
+	within the critical section may observe the effects of any
+	access following the grace period.
+
+	<p>
+	As of late 2016, mathematical models of RCU take this
+	viewpoint, for example, see slides&nbsp;62 and&nbsp;63
+	of the
+	<a href="http://www2.rdrop.com/users/paulmck/scalability/paper/LinuxMM.2016.10.04c.LCE.pdf">2016 LinuxCon EU</a>
+	presentation.
 </font></td></tr>
 <tr><td>&nbsp;</td></tr>
 </table>
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 204422719197..5cbd8b2395b8 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -237,7 +237,7 @@ rcu_dereference()
 
 	The reader uses rcu_dereference() to fetch an RCU-protected
 	pointer, which returns a value that may then be safely
-	dereferenced.  Note that rcu_deference() does not actually
+	dereferenced.  Note that rcu_dereference() does not actually
 	dereference the pointer, instead, it protects the pointer for
 	later dereferencing.  It also executes any needed memory-barrier
 	instructions for a given CPU architecture.  Currently, only Alpha