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Commit 5bda4f63 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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

Pull RCU changes from Ingo Molar:
 "The main changes:

   - torture-test updates
   - callback-offloading changes
   - maintainership changes
   - update RCU documentation
   - miscellaneous fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
  rcu: Allow for NULL tick_nohz_full_mask when nohz_full= missing
  rcu: Fix a sparse warning in rcu_report_unblock_qs_rnp()
  rcu: Fix a sparse warning in rcu_initiate_boost()
  rcu: Fix __rcu_reclaim() to use true/false for bool
  rcu: Remove CONFIG_PROVE_RCU_DELAY
  rcu: Use __this_cpu_read() instead of per_cpu_ptr()
  rcu: Don't use NMIs to dump other CPUs' stacks
  rcu: Bind grace-period kthreads to non-NO_HZ_FULL CPUs
  rcu: Simplify priority boosting by putting rt_mutex in rcu_node
  rcu: Check both root and current rcu_node when setting up future grace period
  rcu: Allow post-unlock reference for rt_mutex
  rcu: Loosen __call_rcu()'s rcu_head alignment constraint
  rcu: Eliminate read-modify-write ACCESS_ONCE() calls
  rcu: Remove redundant ACCESS_ONCE() from tick_do_timer_cpu
  rcu: Make rcu node arrays static const char * const
  signal: Explain local_irq_save() call
  rcu: Handle obsolete references to TINY_PREEMPT_RCU
  rcu: Document deadlock-avoidance information for rcu_read_unlock()
  scripts: Teach get_maintainer.pl about the new "R:" tag
  rcu: Update rcu torture maintainership filename patterns
  ...
parents a45c657f 01c9db82

Documentation/RCU/RTFP.txt

+2 −2
Original line number Diff line number Diff line
@@ -2451,8 +2451,8 @@ lot of {Linux} into your technology!!!" 
,month="February"

,year="2010"

,note="Available:

\url{http://kerneltrap.com/mailarchive/linux-netdev/2010/2/26/6270589}

[Viewed March 20, 2011]"

\url{http://thread.gmane.org/gmane.linux.network/153338}

[Viewed June 9, 2014]"

,annotation={

	Use a pair of list_head structures to support RCU-protected

	resizable hash tables.

Documentation/RCU/rcuref.txt

+9 −0
Original line number Diff line number Diff line 
Reference-count design for elements of lists/arrays protected by RCU.





Please note that the percpu-ref feature is likely your first

stop if you need to combine reference counts and RCU.  Please see

include/linux/percpu-refcount.h for more information.  However, in

those unusual cases where percpu-ref would consume too much memory,

please read on.



------------------------------------------------------------------------



Reference counting on elements of lists which are protected by traditional

reader/writer spinlocks or semaphores are straightforward:

Documentation/kernel-parameters.txt

+7 −0
Original line number Diff line number Diff line
@@ -2813,6 +2813,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			quiescent states.  Units are jiffies, minimum

			value is one, and maximum value is HZ.



	rcutree.rcu_nocb_leader_stride= [KNL]

			Set the number of NOCB kthread groups, which

			defaults to the square root of the number of

			CPUs.  Larger numbers reduces the wakeup overhead

			on the per-CPU grace-period kthreads, but increases

			that same overhead on each group's leader.



	rcutree.qhimark= [KNL]

			Set threshold of queued RCU callbacks beyond which

			batch limiting is disabled.

Documentation/memory-barriers.txt

+23 −4
Original line number Diff line number Diff line
@@ -757,10 +757,14 @@ SMP BARRIER PAIRING 
When dealing with CPU-CPU interactions, certain types of memory barrier should

always be paired.  A lack of appropriate pairing is almost certainly an error.



A write barrier should always be paired with a data dependency barrier or read

barrier, though a general barrier would also be viable.  Similarly a read

barrier or a data dependency barrier should always be paired with at least an

write barrier, though, again, a general barrier is viable:

General barriers pair with each other, though they also pair with

most other types of barriers, albeit without transitivity.  An acquire

barrier pairs with a release barrier, but both may also pair with other

barriers, including of course general barriers.  A write barrier pairs

with a data dependency barrier, an acquire barrier, a release barrier,

a read barrier, or a general barrier.  Similarly a read barrier or a

data dependency barrier pairs with a write barrier, an acquire barrier,

a release barrier, or a general barrier:



	CPU 1		      CPU 2

	===============	      ===============
@@ -1893,6 +1897,21 @@ between the STORE to indicate the event and the STORE to set TASK_RUNNING: 
	    <general barrier>		  STORE current->state

	LOAD event_indicated



To repeat, this write memory barrier is present if and only if something

is actually awakened.  To see this, consider the following sequence of

events, where X and Y are both initially zero:



	CPU 1				CPU 2

	===============================	===============================

	X = 1;				STORE event_indicated

	smp_mb();			wake_up();

	Y = 1;				wait_event(wq, Y == 1);

	wake_up();			  load from Y sees 1, no memory barrier

					load from X might see 0



In contrast, if a wakeup does occur, CPU 2's load from X would be guaranteed

to see 1.



The available waker functions include:



	complete();

MAINTAINERS

+15 −3
Original line number Diff line number Diff line
@@ -70,6 +70,8 @@ Descriptions of section entries: 


	P: Person (obsolete)

	M: Mail patches to: FullName <address@domain>

	R: Designated reviewer: FullName <address@domain>

	   These reviewers should be CCed on patches.

	L: Mailing list that is relevant to this area

	W: Web-page with status/info

	Q: Patchwork web based patch tracking system site
@@ -7443,10 +7445,14 @@ L: linux-kernel@vger.kernel.org 
S:	Supported

T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git

F:	Documentation/RCU/torture.txt

F:	kernel/rcu/torture.c

F:	kernel/rcu/rcutorture.c



RCUTORTURE TEST FRAMEWORK

M:	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

M:	Josh Triplett <josh@joshtriplett.org>

R:	Steven Rostedt <rostedt@goodmis.org>

R:	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

R:	Lai Jiangshan <laijs@cn.fujitsu.com>

L:	linux-kernel@vger.kernel.org

S:	Supported

T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
@@ -7469,8 +7475,11 @@ S: Supported 
F:	net/rds/



READ-COPY UPDATE (RCU)

M:	Dipankar Sarma <dipankar@in.ibm.com>

M:	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

M:	Josh Triplett <josh@joshtriplett.org>

R:	Steven Rostedt <rostedt@goodmis.org>

R:	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

R:	Lai Jiangshan <laijs@cn.fujitsu.com>

L:	linux-kernel@vger.kernel.org

W:	http://www.rdrop.com/users/paulmck/RCU/

S:	Supported
@@ -7480,7 +7489,7 @@ X: Documentation/RCU/torture.txt 
F:	include/linux/rcu*

X:	include/linux/srcu.h

F:	kernel/rcu/

X:	kernel/rcu/torture.c

X:	kernel/torture.c



REAL TIME CLOCK (RTC) SUBSYSTEM

M:	Alessandro Zummo <a.zummo@towertech.it>
@@ -8263,6 +8272,9 @@ F: mm/sl?b* 
SLEEPABLE READ-COPY UPDATE (SRCU)

M:	Lai Jiangshan <laijs@cn.fujitsu.com>

M:	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

M:	Josh Triplett <josh@joshtriplett.org>

R:	Steven Rostedt <rostedt@goodmis.org>

R:	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

L:	linux-kernel@vger.kernel.org

W:	http://www.rdrop.com/users/paulmck/RCU/

S:	Supported