[PATCH tip/core/rcu 0/3] Documentation updates for 3.12

[PATCH tip/core/rcu 0/3] Documentation updates for 3.12

[Paul E. McKenney]

Hello!

This series provides a few documentation updates:

1.	Update rcu_barrier() documentation to note that it no longer is
	guaranteed to wait for a full grace period.  This guarantee was
	a victim of energy efficiency.

2.	Update RTFP documentation.

3.	Fix a control-dependency example in the memory-barriers
	documentation.

							Thanx, Paul


 b/Documentation/RCU/RTFP.txt        |  855 +++++++++++++++++++++++-------------
 b/Documentation/RCU/rcubarrier.txt  |   12 
 b/Documentation/memory-barriers.txt |   10 
 3 files changed, 564 insertions(+), 313 deletions(-)

[PATCH tip/core/rcu 1/3] rcu: Fix rcu_barrier() documentation

[Paul E. McKenney]

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

There was a time when rcu_barrier() was guaranteed to wait for at least
a grace period, but that time ended due to energy-efficiency concerns.
So now rcu_barrier() is a no-op if there are no RCU callbacks queued in
the system.  This commit updates the documentation to reflect this change.

Now, rcu_barrier() often does wait for a grace period, so, one could
imagine some modification to rcu_barrier() to more efficiently handle
cases where both rcu_barrier() and a grace period are needed.  But this
must wait until someone shows a real-world need for a change.

Reported-by: Bob Copeland <bob@cozybit.com>
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 Documentation/RCU/rcubarrier.txt | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/Documentation/RCU/rcubarrier.txt b/Documentation/RCU/rcubarrier.txt
index 2e319d1..b10cfe7 100644
--- a/Documentation/RCU/rcubarrier.txt
+++ b/Documentation/RCU/rcubarrier.txt
@@ -70,10 +70,14 @@ in realtime kernels in order to avoid excessive scheduling latencies.
 
 rcu_barrier()
 
-We instead need the rcu_barrier() primitive. This primitive is similar
-to synchronize_rcu(), but instead of waiting solely for a grace
-period to elapse, it also waits for all outstanding RCU callbacks to
-complete. Pseudo-code using rcu_barrier() is as follows:
+We instead need the rcu_barrier() primitive.  Rather than waiting for
+a grace period to elapse, rcu_barrier() waits for all outstanding RCU
+callbacks to complete.  Please note that rcu_barrier() does -not- imply
+synchronize_rcu(), in particular, if there are no RCU callbacks queued
+anywhere, rcu_barrier() is within its rights to return immediately,
+without waiting for a grace period to elapse.
+
+Pseudo-code using rcu_barrier() is as follows:
 
    1. Prevent any new RCU callbacks from being posted.
    2. Execute rcu_barrier().
-- 
1.8.1.5

[PATCH tip/core/rcu 2/3] rcu: Update RTFP documentation

[Paul E. McKenney]

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

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 Documentation/RCU/RTFP.txt | 855 +++++++++++++++++++++++++++++----------------
 1 file changed, 550 insertions(+), 305 deletions(-)

diff --git a/Documentation/RCU/RTFP.txt b/Documentation/RCU/RTFP.txt
index 7f40c72..350be9a 100644
--- a/Documentation/RCU/RTFP.txt
+++ b/Documentation/RCU/RTFP.txt
@@ -39,7 +39,7 @@ in read-mostly situations.  This algorithm does take pains to avoid
 write-side contention and parallelize the other write-side overheads by
 providing a fine-grained locking design, however, it would be interesting
 to see how much of the performance advantage reported in 1990 remains
-in 2004.
+in 2004 (to say nothing of 2013).
 
 At about this same time, Adams [Adams91] described ``chaotic relaxation'',
 where the normal barriers between successive iterations of convergent
@@ -86,9 +86,9 @@ DYNIX/ptx kernel.  The corresponding conference paper appeared in 1998
 [McKenney98].
 
 In 1999, the Tornado and K42 groups described their "generations"
-mechanism, which quite similar to RCU [Gamsa99].  These operating systems
-made pervasive use of RCU in place of "existence locks", which greatly
-simplifies locking hierarchies.
+mechanism, which is quite similar to RCU [Gamsa99].  These operating
+systems made pervasive use of RCU in place of "existence locks", which
+greatly simplifies locking hierarchies and helps avoid deadlocks.
 
 2001 saw the first RCU presentation involving Linux [McKenney01a]
 at OLS.  The resulting abundance of RCU patches was presented the
@@ -106,8 +106,11 @@ these techniques still impose significant read-side overhead in the
 form of memory barriers.  Researchers at Sun worked along similar lines
 in the same timeframe [HerlihyLM02].  These techniques can be thought
 of as inside-out reference counts, where the count is represented by the
-number of hazard pointers referencing a given data structure (rather than
-the more conventional counter field within the data structure itself).
+number of hazard pointers referencing a given data structure rather than
+the more conventional counter field within the data structure itself.
+The key advantage of inside-out reference counts is that they can be
+stored in immortal variables, thus allowing races between access and
+deletion to be avoided.
 
 By the same token, RCU can be thought of as a "bulk reference count",
 where some form of reference counter covers all reference by a given CPU
@@ -179,7 +182,25 @@ tree using software transactional memory to protect concurrent updates
 (strange, but true!) [PhilHoward2011RCUTMRBTree], yet another variant of
 RCU-protected resizeable hash tables [Triplett:2011:RPHash], the 3.0 RCU
 trainwreck [PaulEMcKenney2011RCU3.0trainwreck], and Neil Brown's "Meet the
-Lockers" LWN article [NeilBrown2011MeetTheLockers].
+Lockers" LWN article [NeilBrown2011MeetTheLockers].  Some academic
+work looked at debugging uses of RCU [Seyster:2011:RFA:2075416.2075425].
+
+In 2012, Josh Triplett received his Ph.D. with his dissertation
+covering RCU-protected resizable hash tables and the relationship
+between memory barriers and read-side traversal order:  If the updater
+is making changes in the opposite direction from the read-side traveral
+order, the updater need only execute a memory-barrier instruction,
+but if in the same direction, the updater needs to wait for a grace
+period between the individual updates [JoshTriplettPhD].  Also in 2012,
+after seventeen years of attempts, an RCU paper made it into a top-flight
+academic journal, IEEE Transactions on Parallel and Distributed Systems
+[MathieuDesnoyers2012URCU].  A group of researchers in Spain applied
+user-level RCU to crowd simulation [GuillermoVigueras2012RCUCrowd], and
+another group of researchers in Europe produced a formal description of
+RCU based on separation logic [AlexeyGotsman2012VerifyGraceExtended],
+which was published in the 2013 European Symposium on Programming
+[AlexeyGotsman2013ESOPRCU].
+
 
 
 Bibtex Entries
@@ -193,13 +214,12 @@ Bibtex Entries
 ,volume="5"
 ,number="3"
 ,pages="354-382"
-,note="Available:
-\url{http://portal.acm.org/citation.cfm?id=320619&dl=GUIDE,}
-[Viewed December 3, 2007]"
 ,annotation={
 	Use garbage collector to clean up data after everyone is done with it.
 	.
 	Oldest use of something vaguely resembling RCU that I have found.
+	http://portal.acm.org/citation.cfm?id=320619&dl=GUIDE,
+	[Viewed December 3, 2007]
 }
 }
 
@@ -309,7 +329,7 @@ for Programming Languages and Operating Systems}"
 ,doi = {http://doi.acm.org/10.1145/42392.42399}
 ,publisher = {ACM}
 ,address = {New York, NY, USA}
-,annotation= {
+,annotation={
 	At the top of page 307: "Conflicts with deposits and withdrawals
 	are necessary if the reported total is to be up to date.  They
 	could be avoided by having total return a sum that is slightly
@@ -346,8 +366,9 @@ for Programming Languages and Operating Systems}"
 }
 }
 
-@Book{Adams91
-,Author="Gregory R. Adams"
+# Was Adams91, see also syncrefs.bib.
+@Book{Andrews91textbook
+,Author="Gregory R. Andrews"
 ,title="Concurrent Programming, Principles, and Practices"
 ,Publisher="Benjamin Cummins"
 ,Year="1991"
@@ -398,39 +419,39 @@ for Programming Languages and Operating Systems}"
 }
 }
 
-@conference{Pu95a,
-Author = "Calton Pu and Tito Autrey and Andrew Black and Charles Consel and
+@conference{Pu95a
+,Author = "Calton Pu and Tito Autrey and Andrew Black and Charles Consel and
 Crispin Cowan and Jon Inouye and Lakshmi Kethana and Jonathan Walpole and
-Ke Zhang",
-Title = "Optimistic Incremental Specialization: Streamlining a Commercial
-Operating System",
-Booktitle = "15\textsuperscript{th} ACM Symposium on
-Operating Systems Principles (SOSP'95)",
-address = "Copper Mountain, CO",
-month="December",
-year="1995",
-pages="314-321",
-annotation="
+Ke Zhang"
+,Title = "Optimistic Incremental Specialization: Streamlining a Commercial
+,Operating System"
+,Booktitle = "15\textsuperscript{th} ACM Symposium on
+,Operating Systems Principles (SOSP'95)"
+,address = "Copper Mountain, CO"
+,month="December"
+,year="1995"
+,pages="314-321"
+,annotation={
 	Uses a replugger, but with a flag to signal when people are
 	using the resource at hand.  Only one reader at a time.
-"
-}
-
-@conference{Cowan96a,
-Author = "Crispin Cowan and Tito Autrey and Charles Krasic and
-Calton Pu and Jonathan Walpole",
-Title = "Fast Concurrent Dynamic Linking for an Adaptive Operating System",
-Booktitle = "International Conference on Configurable Distributed Systems
-(ICCDS'96)",
-address = "Annapolis, MD",
-month="May",
-year="1996",
-pages="108",
-isbn="0-8186-7395-8",
-annotation="
+}
+}
+
+@conference{Cowan96a
+,Author = "Crispin Cowan and Tito Autrey and Charles Krasic and
+,Calton Pu and Jonathan Walpole"
+,Title = "Fast Concurrent Dynamic Linking for an Adaptive Operating System"
+,Booktitle = "International Conference on Configurable Distributed Systems
+(ICCDS'96)"
+,address = "Annapolis, MD"
+,month="May"
+,year="1996"
+,pages="108"
+,isbn="0-8186-7395-8"
+,annotation={
 	Uses a replugger, but with a counter to signal when people are
 	using the resource at hand.  Allows multiple readers.
-"
+}
 }
 
 @techreport{Slingwine95
@@ -493,14 +514,13 @@ Problems"
 ,Year="1998"
 ,pages="509-518"
 ,Address="Las Vegas, NV"
-,note="Available:
-\url{http://www.rdrop.com/users/paulmck/RCU/rclockpdcsproof.pdf}
-[Viewed December 3, 2007]"
 ,annotation={
 	Describes and analyzes RCU mechanism in DYNIX/ptx.  Describes
 	application to linked list update and log-buffer flushing.
 	Defines 'quiescent state'.  Includes both measured and analytic
 	evaluation.
+	http://www.rdrop.com/users/paulmck/RCU/rclockpdcsproof.pdf
+	[Viewed December 3, 2007]
 }
 }
 
@@ -514,13 +534,12 @@ Operating System Design and Implementation}"
 ,Year="1999"
 ,pages="87-100"
 ,Address="New Orleans, LA"
-,note="Available:
-\url{http://www.usenix.org/events/osdi99/full_papers/gamsa/gamsa.pdf}
-[Viewed August 30, 2006]"
 ,annotation={
 	Use of RCU-like facility in K42/Tornado.  Another independent
 	invention of RCU.
 	See especially pages 7-9 (Section 5).
+	http://www.usenix.org/events/osdi99/full_papers/gamsa/gamsa.pdf
+	[Viewed August 30, 2006]
 }
 }
 
@@ -611,9 +630,9 @@ Orran Krieger and Rusty Russell and Dipankar Sarma and Maneesh Soni"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?l=linux-kernel&m=100259266316456&w=2}
 [Viewed June 23, 2004]"
-,annotation="
+,annotation={
 	Memory-barrier and Alpha thread.  100 messages, not too bad...
-"
+}
 }
 
 @unpublished{Spraul01
@@ -624,10 +643,10 @@ Orran Krieger and Rusty Russell and Dipankar Sarma and Maneesh Soni"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?l=linux-kernel&m=100264675012867&w=2}
 [Viewed June 23, 2004]"
-,annotation="
+,annotation={
 	Suggested burying memory barriers in Linux's list-manipulation
 	primitives.
-"
+}
 }
 
 @unpublished{LinusTorvalds2001a
@@ -638,6 +657,8 @@ Orran Krieger and Rusty Russell and Dipankar Sarma and Maneesh Soni"
 ,note="Available:
 \url{http://lkml.org/lkml/2001/10/13/105}
 [Viewed August 21, 2004]"
+,annotation={
+}
 }
 
 @unpublished{Blanchard02a
@@ -657,10 +678,10 @@ Orran Krieger and Rusty Russell and Dipankar Sarma and Maneesh Soni"
 ,Month="June"
 ,Year="2002"
 ,pages="289-300"
-,annotation="
+,annotation={
 	Measured scalability of Linux 2.4 kernel's directory-entry cache
 	(dcache), and measured some scalability enhancements.
-"
+}
 }
 
 @Conference{McKenney02a
@@ -674,10 +695,10 @@ Andrea Arcangeli and Andi Kleen and Orran Krieger and Rusty Russell"
 ,note="Available:
 \url{http://www.linux.org.uk/~ajh/ols2002_proceedings.pdf.gz}
 [Viewed June 23, 2004]"
-,annotation="
+,annotation={
 	Presented and compared a number of RCU implementations for the
 	Linux kernel.
-"
+}
 }
 
 @unpublished{Sarma02a
@@ -688,9 +709,9 @@ Andrea Arcangeli and Andi Kleen and Orran Krieger and Rusty Russell"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?l=linux-kernel&m=102645767914212&w=2}
 [Viewed June 23, 2004]"
-,annotation="
+,annotation={
 	Compare fastwalk and RCU for dcache.  RCU won.
-"
+}
 }
 
 @unpublished{Barbieri02
@@ -701,9 +722,9 @@ Andrea Arcangeli and Andi Kleen and Orran Krieger and Rusty Russell"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?l=linux-kernel&m=103082050621241&w=2}
 [Viewed: June 23, 2004]"
-,annotation="
+,annotation={
 	Suggested RCU for vfs\_shared\_cred.
-"
+}
 }
 
 @unpublished{Dickins02a
@@ -722,10 +743,10 @@ Andrea Arcangeli and Andi Kleen and Orran Krieger and Rusty Russell"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?l=linux-kernel&m=103462075416638&w=2}
 [Viewed June 23, 2004]"
-,annotation="
+,annotation={
 	Performance of dcache RCU on kernbench for 16x NUMA-Q and 1x,
 	2x, and 4x systems.  RCU does no harm, and helps on 16x.
-"
+}
 }
 
 @unpublished{LinusTorvalds2003a
@@ -736,14 +757,14 @@ Andrea Arcangeli and Andi Kleen and Orran Krieger and Rusty Russell"
 ,note="Available:
 \url{http://lkml.org/lkml/2003/3/9/205}
 [Viewed March 13, 2006]"
-,annotation="
+,annotation={
 	Linus suggests replacing brlock with RCU and/or seqlocks:
 	.
 	'It's entirely possible that the current user could be replaced
 	by RCU and/or seqlocks, and we could get rid of brlocks entirely.'
 	.
 	Steve Hemminger responds by replacing them with RCU.
-"
+}
 }
 
 @article{Appavoo03a
@@ -758,9 +779,9 @@ B. Rosenburg and M. Stumm and J. Xenidis"
 ,volume="42"
 ,number="1"
 ,pages="60-76"
-,annotation="
+,annotation={
 	Use of RCU to enable hot-swapping for autonomic behavior in K42.
-"
+}
 }
 
 @unpublished{Seigh03
@@ -769,9 +790,9 @@ B. Rosenburg and M. Stumm and J. Xenidis"
 ,Year="2003"
 ,Month="March"
 ,note="email correspondence"
-,annotation="
+,annotation={
 	Described the relationship of the VM/XA passive serialization to RCU.
-"
+}
 }
 
 @Conference{Arcangeli03
@@ -785,14 +806,12 @@ Dipankar Sarma"
 ,year="2003"
 ,month="June"
 ,pages="297-310"
-,note="Available:
-\url{http://www.rdrop.com/users/paulmck/RCU/rcu.FREENIX.2003.06.14.pdf}
-[Viewed November 21, 2007]"
-,annotation="
+,annotation={
 	Compared updated RCU implementations for the Linux kernel, and
 	described System V IPC use of RCU, including order-of-magnitude
 	performance improvements.
-"
+	http://www.rdrop.com/users/paulmck/RCU/rcu.FREENIX.2003.06.14.pdf
+}
 }
 
 @Conference{Soules03a
@@ -820,10 +839,10 @@ Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis"
 ,note="Available:
 \url{http://www.linuxjournal.com/article/6993}
 [Viewed November 14, 2007]"
-,annotation="
+,annotation={
 	Reader-friendly intro to RCU, with the infamous old-man-and-brat
 	cartoon.
-"
+}
 }
 
 @unpublished{Sarma03a
@@ -832,7 +851,9 @@ Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis"
 ,month="December"
 ,year="2003"
 ,note="Message ID: 20031222180114.GA2248@in.ibm.com"
-,annotation="dipankar/ct.2004.03.27/RCUll.2003.12.22.patch"
+,annotation={
+	dipankar/ct.2004.03.27/RCUll.2003.12.22.patch
+}
 }
 
 @techreport{Friedberg03a
@@ -844,11 +865,11 @@ Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis"
 ,number="US Patent 6,662,184"
 ,month="December"
 ,pages="112"
-,annotation="
+,annotation={
 	Applies RCU to a wildcard-search Patricia tree in order to permit
 	synchronization-free lookup.  RCU is used to retain removed nodes
 	for a grace period before freeing them.
-"
+}
 }
 
 @article{McKenney04a
@@ -860,12 +881,11 @@ Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis"
 ,volume="1"
 ,number="118"
 ,pages="38-46"
-,note="Available:
-\url{http://www.linuxjournal.com/node/7124}
-[Viewed December 26, 2010]"
-,annotation="
+,annotation={
 	Reader friendly intro to dcache and RCU.
-"
+	http://www.linuxjournal.com/node/7124
+	[Viewed December 26, 2010]
+}
 }
 
 @Conference{McKenney04b
@@ -879,10 +899,10 @@ Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis"
 \url{http://www.linux.org.au/conf/2004/abstracts.html#90}
 \url{http://www.rdrop.com/users/paulmck/RCU/lockperf.2004.01.17a.pdf}
 [Viewed June 23, 2004]"
-,annotation="
+,annotation={
 	Compares performance of RCU to that of other locking primitives
 	over a number of CPUs (x86, Opteron, Itanium, and PPC).
-"
+}
 }
 
 @unpublished{Sarma04a
@@ -891,7 +911,9 @@ Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis"
 ,month="March"
 ,year="2004"
 ,note="\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=108003746402892&w=2}"
-,annotation="Head of thread: dipankar/2004.03.23/rcu-low-lat.1.patch"
+,annotation={
+	Head of thread: dipankar/2004.03.23/rcu-low-lat.1.patch
+}
 }
 
 @unpublished{Sarma04b
@@ -900,7 +922,9 @@ Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis"
 ,month="March"
 ,year="2004"
 ,note="\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=108016474829546&w=2}"
-,annotation="dipankar/rcuth.2004.03.24/rcu-throttle.patch"
+,annotation={
+	dipankar/rcuth.2004.03.24/rcu-throttle.patch
+}
 }
 
 @unpublished{Spraul04a
@@ -911,9 +935,9 @@ Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?l=linux-kernel&m=108546407726602&w=2}
 [Viewed June 23, 2004]"
-,annotation="
+,annotation={
 	Hierarchical-bitmap patch for RCU infrastructure.
-"
+}
 }
 
 @unpublished{Steiner04a
@@ -950,10 +974,12 @@ Realtime Applications"
 ,year="2004"
 ,month="June"
 ,pages="182-191"
-,annotation="
+,annotation={
 	Describes and compares a number of modifications to the Linux RCU
 	implementation that make it friendly to realtime applications.
-"
+	https://www.usenix.org/conference/2004-usenix-annual-technical-conference/making-rcu-safe-deep-sub-millisecond-response
+	[Viewed July 26, 2012]
+}
 }
 
 @phdthesis{PaulEdwardMcKenneyPhD
@@ -964,14 +990,13 @@ in Operating System Kernels"
 ,school="OGI School of Science and Engineering at
 Oregon Health and Sciences University"
 ,year="2004"
-,note="Available:
-\url{http://www.rdrop.com/users/paulmck/RCU/RCUdissertation.2004.07.14e1.pdf}
-[Viewed October 15, 2004]"
-,annotation="
+,annotation={
 	Describes RCU implementations and presents design patterns
 	corresponding to common uses of RCU in several operating-system
 	kernels.
-"
+	http://www.rdrop.com/users/paulmck/RCU/RCUdissertation.2004.07.14e1.pdf
+	[Viewed October 15, 2004]
+}
 }
 
 @unpublished{PaulEMcKenney2004rcu:dereference
@@ -982,9 +1007,9 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://lkml.org/lkml/2004/8/6/237}
 [Viewed June 8, 2010]"
-,annotation="
+,annotation={
 	Introduce rcu_dereference().
-"
+}
 }
 
 @unpublished{JimHouston04a
@@ -995,11 +1020,11 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://lkml.org/lkml/2004/8/30/87}
 [Viewed February 17, 2005]"
-,annotation="
+,annotation={
 	Uses active code in rcu_read_lock() and rcu_read_unlock() to
 	make RCU happen, allowing RCU to function on CPUs that do not
 	receive a scheduling-clock interrupt.
-"
+}
 }
 
 @unpublished{TomHart04a
@@ -1010,9 +1035,9 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://www.cs.toronto.edu/~tomhart/masters_thesis.html}
 [Viewed October 15, 2004]"
-,annotation="
+,annotation={
 	Proposes comparing RCU to lock-free methods for the Linux kernel.
-"
+}
 }
 
 @unpublished{Vaddagiri04a
@@ -1023,9 +1048,9 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?t=109395731700004&r=1&w=2}
 [Viewed October 18, 2004]"
-,annotation="
+,annotation={
 	Srivatsa's RCU patch for tcp_ehash lookup.
-"
+}
 }
 
 @unpublished{Thirumalai04a
@@ -1036,9 +1061,9 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?t=109144217400003&r=1&w=2}
 [Viewed October 18, 2004]"
-,annotation="
+,annotation={
 	Ravikiran's lockfree FD patch.
-"
+}
 }
 
 @unpublished{Thirumalai04b
@@ -1049,9 +1074,9 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://marc.theaimsgroup.com/?l=linux-kernel&m=109152521410459&w=2}
 [Viewed October 18, 2004]"
-,annotation="
+,annotation={
 	Ravikiran's lockfree FD patch.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2004rcu:assign:pointer
@@ -1062,9 +1087,9 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://lkml.org/lkml/2004/10/23/241}
 [Viewed June 8, 2010]"
-,annotation="
+,annotation={
 	Introduce rcu_assign_pointer().
-"
+}
 }
 
 @unpublished{JamesMorris04a
@@ -1073,12 +1098,12 @@ Oregon Health and Sciences University"
 ,day="15"
 ,month="November"
 ,year="2004"
-,note="Available:
-\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=110054979416004&w=2}
-[Viewed December 10, 2004]"
-,annotation="
+,note="\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=110054979416004&w=2}"
+,annotation={
 	James Morris posts Kaigai Kohei's patch to LKML.
-"
+	[Viewed December 10, 2004]
+	Kaigai's patch is at https://lkml.org/lkml/2004/9/27/52
+}
 }
 
 @unpublished{JamesMorris04b
@@ -1089,9 +1114,9 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://www.livejournal.com/users/james_morris/2153.html}
 [Viewed December 10, 2004]"
-,annotation="
+,annotation={
 	RCU helps SELinux performance.  ;-)  Made LWN.
-"
+}
 }
 
 @unpublished{PaulMcKenney2005RCUSemantics
@@ -1103,9 +1128,9 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/rcu-semantics.2005.01.30a.pdf}
 [Viewed December 6, 2009]"
-,annotation="
+,annotation={
 	Early derivation of RCU semantics.
-"
+}
 }
 
 @unpublished{PaulMcKenney2005e
@@ -1117,10 +1142,10 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://lkml.org/lkml/2005/3/17/199}
 [Viewed September 5, 2005]"
-,annotation="
+,annotation={
 	First posting showing how RCU can be safely adapted for
 	preemptable RCU read side critical sections.
-"
+}
 }
 
 @unpublished{EsbenNeilsen2005a
@@ -1132,12 +1157,12 @@ Oregon Health and Sciences University"
 ,note="Available:
 \url{http://lkml.org/lkml/2005/3/18/122}
 [Viewed March 30, 2006]"
-,annotation="
+,annotation={
 	Esben Neilsen suggests read-side suppression of grace-period
 	processing for crude-but-workable realtime RCU.  The downside
-	is indefinite grace periods...But this is OK for experimentation
+	is indefinite grace periods...  But this is OK for experimentation
 	and testing.
-"
+}
 }
 
 @unpublished{TomHart05a
@@ -1149,10 +1174,10 @@ Data Structures"
 ,note="Available:
 \url{ftp://ftp.cs.toronto.edu/csrg-technical-reports/515/}
 [Viewed March 4, 2005]"
-,annotation="
+,annotation={
 	Comparison of RCU, QBSR, and EBSR.  RCU wins for read-mostly
 	workloads.  ;-)
-"
+}
 }
 
 @unpublished{JonCorbet2005DeprecateSyncKernel
@@ -1164,10 +1189,10 @@ Data Structures"
 ,note="Available:
 \url{http://lwn.net/Articles/134484/}
 [Viewed May 3, 2005]"
-,annotation="
+,annotation={
 	Jon Corbet describes deprecation of synchronize_kernel()
 	in favor of synchronize_rcu() and synchronize_sched().
-"
+}
 }
 
 @unpublished{PaulMcKenney05a
@@ -1178,10 +1203,10 @@ Data Structures"
 ,note="Available:
 \url{http://lkml.org/lkml/2005/5/9/185}
 [Viewed May 13, 2005]"
-,annotation="
+,annotation={
 	First publication of working lock-based deferred free patches
 	for the CONFIG_PREEMPT_RT environment.
-"
+}
 }
 
 @conference{PaulMcKenney05b
@@ -1194,10 +1219,10 @@ Data Structures"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/realtimeRCU.2005.04.23a.pdf}
 [Viewed May 13, 2005]"
-,annotation="
+,annotation={
 	Realtime turns into making RCU yet more realtime friendly.
 	http://lca2005.linux.org.au/Papers/Paul%20McKenney/Towards%20Hard%20Realtime%20Response%20from%20the%20Linux%20Kernel/LKS.2005.04.22a.pdf
-"
+}
 }
 
 @unpublished{PaulEMcKenneyHomePage
@@ -1208,9 +1233,9 @@ Data Structures"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/}
 [Viewed May 25, 2005]"
-,annotation="
+,annotation={
 	Paul McKenney's home page.
-"
+}
 }
 
 @unpublished{PaulEMcKenneyRCUPage
@@ -1221,9 +1246,9 @@ Data Structures"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU}
 [Viewed May 25, 2005]"
-,annotation="
+,annotation={
 	Paul McKenney's RCU page.
-"
+}
 }
 
 @unpublished{JosephSeigh2005a
@@ -1232,10 +1257,10 @@ Data Structures"
 ,month="July"
 ,year="2005"
 ,note="Personal communication"
-,annotation="
+,annotation={
 	Joe Seigh announcing his atomic-ptr-plus project.
 	http://sourceforge.net/projects/atomic-ptr-plus/
-"
+}
 }
 
 @unpublished{JosephSeigh2005b
@@ -1247,9 +1272,9 @@ Data Structures"
 ,note="Available:
 \url{http://sourceforge.net/projects/atomic-ptr-plus/}
 [Viewed August 8, 2005]"
-,annotation="
+,annotation={
 	Joe Seigh's atomic-ptr-plus project.
-"
+}
 }
 
 @unpublished{PaulMcKenney2005c
@@ -1261,9 +1286,9 @@ Data Structures"
 ,note="Available:
 \url{http://lkml.org/lkml/2005/8/1/155}
 [Viewed March 14, 2006]"
-,annotation="
+,annotation={
 	First operating counter-based realtime RCU patch posted to LKML.
-"
+}
 }
 
 @unpublished{PaulMcKenney2005d
@@ -1275,11 +1300,11 @@ Data Structures"
 ,note="Available:
 \url{http://lkml.org/lkml/2005/8/8/108}
 [Viewed March 14, 2006]"
-,annotation="
+,annotation={
 	First operating counter-based realtime RCU patch posted to LKML,
 	but fixed so that various unusual combinations of configuration
 	parameters all function properly.
-"
+}
 }
 
 @unpublished{PaulMcKenney2005rcutorture
@@ -1291,9 +1316,25 @@ Data Structures"
 ,note="Available:
 \url{http://lkml.org/lkml/2005/10/1/70}
 [Viewed March 14, 2006]"
-,annotation="
+,annotation={
 	First rcutorture patch.
-"
+}
+}
+
+@unpublished{DavidSMiller2006HashedLocking
+,Author="David S. Miller"
+,Title="Re: [{PATCH}, {RFC}] {RCU} : {OOM} avoidance and lower latency"
+,month="January"
+,day="6"
+,year="2006"
+,note="Available:
+\url{https://lkml.org/lkml/2006/1/7/22}
+[Viewed February 29, 2012]"
+,annotation={
+	David Miller's view on hashed arrays of locks: used to really
+	like it, but time he saw an opportunity for this technique,
+	something else always proved superior.  Partitioning or RCU.  ;-)
+}
 }
 
 @conference{ThomasEHart2006a
@@ -1309,10 +1350,10 @@ Distributed Processing Symposium"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/hart_ipdps06.pdf}
 [Viewed April 28, 2008]"
-,annotation="
+,annotation={
 	Compares QSBR, HPBR, EBR, and lock-free reference counting.
 	http://www.cs.toronto.edu/~tomhart/perflab/ipdps06.tgz
-"
+}
 }
 
 @unpublished{NickPiggin2006radixtree
@@ -1324,9 +1365,9 @@ Distributed Processing Symposium"
 ,note="Available:
 \url{http://lkml.org/lkml/2006/6/20/238}
 [Viewed March 25, 2008]"
-,annotation="
+,annotation={
 	RCU-protected radix tree.
-"
+}
 }
 
 @Conference{PaulEMcKenney2006b
@@ -1341,9 +1382,9 @@ Suparna Bhattacharya"
 \url{http://www.linuxsymposium.org/2006/view_abstract.php?content_key=184}
 \url{http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf}
 [Viewed January 1, 2007]"
-,annotation="
+,annotation={
 	Described how to improve the -rt implementation of realtime RCU.
-"
+}
 }
 
 @unpublished{WikipediaRCU
@@ -1354,12 +1395,11 @@ Canis Rufus and Zoicon5 and Anome and Hal Eisen"
 ,month="July"
 ,day="8"
 ,year="2006"
-,note="Available:
-\url{http://en.wikipedia.org/wiki/Read-copy-update}
-[Viewed August 21, 2006]"
-,annotation="
+,note="\url{http://en.wikipedia.org/wiki/Read-copy-update}"
+,annotation={
 	Wikipedia RCU page as of July 8 2006.
-"
+	[Viewed August 21, 2006]
+}
 }
 
 @Conference{NickPiggin2006LocklessPageCache
@@ -1372,9 +1412,9 @@ Canis Rufus and Zoicon5 and Anome and Hal Eisen"
 ,note="Available:
 \url{http://www.linuxsymposium.org/2006/view_abstract.php?content_key=184}
 [Viewed January 11, 2009]"
-,annotation="
+,annotation={
 	Uses RCU-protected radix tree for a lockless page cache.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2006c
@@ -1388,9 +1428,9 @@ Canis Rufus and Zoicon5 and Anome and Hal Eisen"
 Revised:
 \url{http://www.rdrop.com/users/paulmck/RCU/srcu.2007.01.14a.pdf}
 [Viewed August 21, 2006]"
-,annotation="
+,annotation={
 	LWN article introducing SRCU.
-"
+}
 }
 
 @unpublished{RobertOlsson2006a
@@ -1399,12 +1439,11 @@ Revised:
 ,month="August"
 ,day="18"
 ,year="2006"
-,note="Available:
-\url{http://www.nada.kth.se/~snilsson/publications/TRASH/trash.pdf}
-[Viewed March 4, 2011]"
-,annotation="
+,note="\url{http://www.nada.kth.se/~snilsson/publications/TRASH/trash.pdf}"
+,annotation={
 	RCU-protected dynamic trie-hash combination.
-"
+	[Viewed March 4, 2011]
+}
 }
 
 @unpublished{ChristophHellwig2006RCU2SRCU
@@ -1426,10 +1465,10 @@ Revised:
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/linuxusage.html}
 [Viewed January 14, 2007]"
-,annotation="
+,annotation={
 	Paul McKenney's RCU page showing graphs plotting Linux-kernel
 	usage of RCU.
-"
+}
 }
 
 @unpublished{PaulEMcKenneyRCUusageRawDataPage
@@ -1440,10 +1479,10 @@ Revised:
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/linuxusage/rculocktab.html}
 [Viewed January 14, 2007]"
-,annotation="
+,annotation={
 	Paul McKenney's RCU page showing Linux usage of RCU in tabular
 	form, with links to corresponding cscope databases.
-"
+}
 }
 
 @unpublished{GauthamShenoy2006RCUrwlock
@@ -1455,13 +1494,13 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2006/10/26/73}
 [Viewed January 26, 2009]"
-,annotation="
+,annotation={
 	RCU-based reader-writer lock that allows readers to proceed with
 	no memory barriers or atomic instruction in absence of writers.
 	If writer do show up, readers must of course wait as required by
 	the semantics of reader-writer locking.  This is a recursive
 	lock.
-"
+}
 }
 
 @unpublished{JensAxboe2006SlowSRCU
@@ -1474,11 +1513,11 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2006/11/17/56}
 [Viewed May 28, 2007]"
-,annotation="
+,annotation={
 	SRCU's grace periods are too slow for Jens, even after a
 	factor-of-three speedup.
 	Sped-up version of SRCU at http://lkml.org/lkml/2006/11/17/359.
-"
+}
 }
 
 @unpublished{OlegNesterov2006QRCU
@@ -1491,10 +1530,10 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2006/11/19/69}
 [Viewed May 28, 2007]"
-,annotation="
+,annotation={
 	First cut of QRCU.  Expanded/corrected versions followed.
 	Used to be OlegNesterov2007QRCU, now time-corrected.
-"
+}
 }
 
 @unpublished{OlegNesterov2006aQRCU
@@ -1506,10 +1545,10 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2006/11/29/330}
 [Viewed November 26, 2008]"
-,annotation="
+,annotation={
 	Expanded/corrected version of QRCU.
 	Used to be OlegNesterov2007aQRCU, now time-corrected.
-"
+}
 }
 
 @unpublished{EvgeniyPolyakov2006RCUslowdown
@@ -1521,10 +1560,10 @@ Revised:
 ,note="Available:
 \url{http://www.ioremap.net/node/41}
 [Viewed October 28, 2008]"
-,annotation="
+,annotation={
 	Using RCU as a pure delay leads to a 2.5x slowdown in skbs in
 	the Linux kernel.
-"
+}
 }
 
 @inproceedings{ChrisMatthews2006ClusteredObjectsRCU
@@ -1541,7 +1580,8 @@ Revised:
 ,annotation={
 	Uses K42's RCU-like functionality to manage clustered-object
 	lifetimes.
-}}
+}
+}
 
 @article{DilmaDaSilva2006K42
 ,author = {Silva, Dilma Da and Krieger, Orran and Wisniewski, Robert W. and Waterland, Amos and Tam, David and Baumann, Andrew}
@@ -1557,7 +1597,8 @@ Revised:
 ,address = {New York, NY, USA}
 ,annotation={
 	Describes relationship of K42 generations to RCU.
-}}
+}
+}
 
 # CoreyMinyard2007list_splice_rcu
 @unpublished{CoreyMinyard2007list:splice:rcu
@@ -1569,9 +1610,9 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2007/1/3/112}
 [Viewed May 28, 2007]"
-,annotation="
+,annotation={
 	Patch for list_splice_rcu().
-"
+}
 }
 
 @unpublished{PaulEMcKenney2007rcubarrier
@@ -1583,9 +1624,9 @@ Revised:
 ,note="Available:
 \url{http://lwn.net/Articles/217484/}
 [Viewed November 22, 2007]"
-,annotation="
+,annotation={
 	LWN article introducing the rcu_barrier() primitive.
-"
+}
 }
 
 @unpublished{PeterZijlstra2007SyncBarrier
@@ -1597,10 +1638,10 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2007/1/28/34}
 [Viewed March 27, 2008]"
-,annotation="
+,annotation={
 	RCU-like implementation for frequent updaters and rare readers(!).
 	Subsumed into QRCU.  Maybe...
-"
+}
 }
 
 @unpublished{PaulEMcKenney2007BoostRCU
@@ -1609,14 +1650,13 @@ Revised:
 ,month="February"
 ,day="5"
 ,year="2007"
-,note="Available:
-\url{http://lwn.net/Articles/220677/}
-Revised:
-\url{http://www.rdrop.com/users/paulmck/RCU/RCUbooststate.2007.04.16a.pdf}
-[Viewed September 7, 2007]"
-,annotation="
+,note="\url{http://lwn.net/Articles/220677/}"
+,annotation={
 	LWN article introducing RCU priority boosting.
-"
+	Revised:
+	http://www.rdrop.com/users/paulmck/RCU/RCUbooststate.2007.04.16a.pdf
+	[Viewed September 7, 2007]
+}
 }
 
 @unpublished{PaulMcKenney2007QRCUpatch
@@ -1628,9 +1668,9 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2007/2/25/18}
 [Viewed March 27, 2008]"
-,annotation="
+,annotation={
 	Patch for QRCU supplying lock-free fast path.
-"
+}
 }
 
 @article{JonathanAppavoo2007K42RCU
@@ -1647,7 +1687,8 @@ Revised:
 ,address = {New York, NY, USA}
 ,annotation={
 	Role of RCU in K42.
-}}
+}
+}
 
 @conference{RobertOlsson2007Trash
 ,Author="Robert Olsson and Stefan Nilsson"
@@ -1658,9 +1699,9 @@ Revised:
 ,note="Available:
 \url{http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4281239}
 [Viewed October 1, 2010]"
-,annotation="
+,annotation={
 	RCU-protected dynamic trie-hash combination.
-"
+}
 }
 
 @conference{PeterZijlstra2007ConcurrentPagecacheRCU
@@ -1673,10 +1714,10 @@ Revised:
 ,note="Available:
 \url{http://ols.108.redhat.com/2007/Reprints/zijlstra-Reprint.pdf}
 [Viewed April 14, 2008]"
-,annotation="
+,annotation={
 	Page-cache modifications permitting RCU readers and concurrent
 	updates.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2007whatisRCU
@@ -1701,11 +1742,11 @@ Revised:
 ,note="Available:
 \url{http://lwn.net/Articles/243851/}
 [Viewed September 8, 2007]"
-,annotation="
+,annotation={
 	LWN article describing Promela and spin, and also using Oleg
 	Nesterov's QRCU as an example (with Paul McKenney's fastpath).
 	Merged patch at: http://lkml.org/lkml/2007/2/25/18
-"
+}
 }
 
 @unpublished{PaulEMcKenney2007WG21DDOatomics
@@ -1714,12 +1755,12 @@ Revised:
 ,month="August"
 ,day="3"
 ,year="2007"
-,note="Preprint:
+,note="Available:
 \url{http://open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2664.htm}
 [Viewed December 7, 2009]"
-,annotation="
+,annotation={
 	RCU for C++, parts 1 and 2.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2007WG21DDOannotation
@@ -1728,12 +1769,12 @@ Revised:
 ,month="September"
 ,day="18"
 ,year="2008"
-,note="Preprint:
+,note="Available:
 \url{http://open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2782.htm}
 [Viewed December 7, 2009]"
-,annotation="
+,annotation={
 	RCU for C++, part 2, updated many times.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2007PreemptibleRCUPatch
@@ -1745,10 +1786,10 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2007/9/10/213}
 [Viewed October 25, 2007]"
-,annotation="
+,annotation={
 	Final patch for preemptable RCU to -rt.  (Later patches were
 	to mainline, eventually incorporated.)
-"
+}
 }
 
 @unpublished{PaulEMcKenney2007PreemptibleRCU
@@ -1760,9 +1801,9 @@ Revised:
 ,note="Available:
 \url{http://lwn.net/Articles/253651/}
 [Viewed October 25, 2007]"
-,annotation="
+,annotation={
 	LWN article describing the design of preemptible RCU.
-"
+}
 }
 
 @article{ThomasEHart2007a
@@ -1783,6 +1824,7 @@ Revised:
 }
 }
 
+# MathieuDesnoyers2007call_rcu_schedNeeded
 @unpublished{MathieuDesnoyers2007call:rcu:schedNeeded
 ,Author="Mathieu Desnoyers"
 ,Title="Re: [patch 1/2] {Linux} Kernel Markers - Support Multiple Probes"
@@ -1792,9 +1834,9 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2007/12/20/244}
 [Viewed March 27, 2008]"
-,annotation="
+,annotation={
 	Request for call_rcu_sched() and rcu_barrier_sched().
-"
+}
 }
 
 
@@ -1815,11 +1857,11 @@ Revised:
 ,note="Available:
 \url{http://lwn.net/Articles/262464/}
 [Viewed December 27, 2007]"
-,annotation="
+,annotation={
 	Lays out the three basic components of RCU: (1) publish-subscribe,
 	(2) wait for pre-existing readers to complete, and (2) maintain
 	multiple versions.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2008WhatIsRCUUsage
@@ -1831,7 +1873,7 @@ Revised:
 ,note="Available:
 \url{http://lwn.net/Articles/263130/}
 [Viewed January 4, 2008]"
-,annotation="
+,annotation={
 	Lays out six uses of RCU:
 	1. RCU is a Reader-Writer Lock Replacement
 	2. RCU is a Restricted Reference-Counting Mechanism
@@ -1839,7 +1881,7 @@ Revised:
 	4. RCU is a Poor Man's Garbage Collector
 	5. RCU is a Way of Providing Existence Guarantees
 	6. RCU is a Way of Waiting for Things to Finish
-"
+}
 }
 
 @unpublished{PaulEMcKenney2008WhatIsRCUAPI
@@ -1851,10 +1893,10 @@ Revised:
 ,note="Available:
 \url{http://lwn.net/Articles/264090/}
 [Viewed January 10, 2008]"
-,annotation="
+,annotation={
 	Gives an overview of the Linux-kernel RCU API and a brief annotated RCU
 	bibliography.
-"
+}
 }
 
 #
@@ -1872,10 +1914,10 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2008/1/29/208}
 [Viewed March 27, 2008]"
-,annotation="
+,annotation={
 	Patch that prevents preemptible RCU from unnecessarily waking
 	up dynticks-idle CPUs.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2008LKMLDependencyOrdering
@@ -1887,9 +1929,9 @@ Revised:
 ,note="Available:
 \url{http://lkml.org/lkml/2008/2/2/255}
 [Viewed October 18, 2008]"
-,annotation="
+,annotation={
 	Explanation of compilers violating dependency ordering.
-"
+}
 }
 
 @Conference{PaulEMcKenney2008Beijing
@@ -1916,24 +1958,26 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lwn.net/Articles/279077/}
 [Viewed April 24, 2008]"
-,annotation="
+,annotation={
 	Describes use of Promela and Spin to validate (and fix!) the
 	dynticks/RCU interface.
-"
+}
 }
 
 @article{DinakarGuniguntala2008IBMSysJ
 ,author="D. Guniguntala and P. E. McKenney and J. Triplett and J. Walpole"
 ,title="The read-copy-update mechanism for supporting real-time applications on shared-memory multiprocessor systems with {Linux}"
 ,Year="2008"
-,Month="April-June"
+,Month="May"
 ,journal="IBM Systems Journal"
 ,volume="47"
 ,number="2"
 ,pages="221-236"
-,annotation="
+,annotation={
 	RCU, realtime RCU, sleepable RCU, performance.
-"
+	http://www.research.ibm.com/journal/sj/472/guniguntala.pdf
+	[Viewed April 24, 2008]
+}
 }
 
 @unpublished{LaiJiangshan2008NewClassicAlgorithm
@@ -1945,11 +1989,11 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lkml.org/lkml/2008/6/2/539}
 [Viewed December 10, 2008]"
-,annotation="
+,annotation={
 	Updated RCU classic algorithm.  Introduced multi-tailed list
 	for RCU callbacks and also pulling common code into
 	__call_rcu().
-"
+}
 }
 
 @article{PaulEMcKenney2008RCUOSR
@@ -1966,6 +2010,7 @@ lot of {Linux} into your technology!!!"
 ,address="New York, NY, USA"
 ,annotation={
 	Linux changed RCU to a far greater degree than RCU has changed Linux.
+	http://portal.acm.org/citation.cfm?doid=1400097.1400099
 }
 }
 
@@ -1978,10 +2023,10 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lkml.org/lkml/2008/8/21/336}
 [Viewed December 8, 2008]"
-,annotation="
+,annotation={
 	State-based RCU.  One key thing that this patch does is to
 	separate the dynticks handling of NMIs and IRQs.
-"
+}
 }
 
 @unpublished{ManfredSpraul2008dyntickIRQNMI
@@ -1993,12 +2038,13 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lkml.org/lkml/2008/9/6/86}
 [Viewed December 8, 2008]"
-,annotation="
+,annotation={
 	Manfred notes a fix required to my attempt to separate irq
 	and NMI processing for hierarchical RCU's dynticks interface.
-"
+}
 }
 
+# Was PaulEMcKenney2011cyclicRCU
 @techreport{PaulEMcKenney2008cyclicRCU
 ,author="Paul E. McKenney"
 ,title="Efficient Support of Consistent Cyclic Search With Read-Copy Update"
@@ -2008,11 +2054,11 @@ lot of {Linux} into your technology!!!"
 ,number="US Patent 7,426,511"
 ,month="September"
 ,pages="23"
-,annotation="
+,annotation={
 	Maintains an additional level of indirection to allow
 	readers to confine themselves to the desired snapshot of the
 	data structure.  Only permits one update at a time.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2008HierarchicalRCU
@@ -2021,13 +2067,12 @@ lot of {Linux} into your technology!!!"
 ,month="November"
 ,day="3"
 ,year="2008"
-,note="Available:
-\url{http://lwn.net/Articles/305782/}
-[Viewed November 6, 2008]"
-,annotation="
+,note="\url{http://lwn.net/Articles/305782/}"
+,annotation={
 	RCU with combining-tree-based grace-period detection,
 	permitting it to handle thousands of CPUs.
-"
+	[Viewed November 6, 2008]
+}
 }
 
 @unpublished{PaulEMcKenney2009BloatwatchRCU
@@ -2039,10 +2084,10 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lkml.org/lkml/2009/1/14/449}
 [Viewed January 15, 2009]"
-,annotation="
+,annotation={
 	Small-footprint implementation of RCU for uniprocessor
 	embedded applications -- and also for exposition purposes.
-"
+}
 }
 
 @conference{PaulEMcKenney2009MaliciousURCU
@@ -2055,9 +2100,9 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/urcutorture.2009.01.22a.pdf}
 [Viewed February 2, 2009]"
-,annotation="
+,annotation={
 	Realtime RCU and torture-testing RCU uses.
-"
+}
 }
 
 @unpublished{MathieuDesnoyers2009URCU
@@ -2066,16 +2111,14 @@ lot of {Linux} into your technology!!!"
 ,month="February"
 ,day="5"
 ,year="2009"
-,note="Available:
-\url{http://lkml.org/lkml/2009/2/5/572}
-\url{http://lttng.org/urcu}
-[Viewed February 20, 2009]"
-,annotation="
+,note="\url{http://lttng.org/urcu}"
+,annotation={
 	Mathieu Desnoyers's user-space RCU implementation.
 	git://lttng.org/userspace-rcu.git
 	http://lttng.org/cgi-bin/gitweb.cgi?p=userspace-rcu.git
 	http://lttng.org/urcu
-"
+	http://lkml.org/lkml/2009/2/5/572
+}
 }
 
 @unpublished{PaulEMcKenney2009LWNBloatWatchRCU
@@ -2087,9 +2130,24 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lwn.net/Articles/323929/}
 [Viewed March 20, 2009]"
-,annotation="
+,annotation={
 	Uniprocessor assumptions allow simplified RCU implementation.
-"
+}
+}
+
+@unpublished{EvgeniyPolyakov2009EllipticsNetwork
+,Author="Evgeniy Polyakov"
+,Title="The Elliptics Network"
+,month="April"
+,day="17"
+,year="2009"
+,note="Available:
+\url{http://www.ioremap.net/projects/elliptics}
+[Viewed April 30, 2009]"
+,annotation={
+	Distributed hash table with transactions, using elliptic
+	hash functions to distribute data.
+}
 }
 
 @unpublished{PaulEMcKenney2009expeditedRCU
@@ -2101,9 +2159,9 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lkml.org/lkml/2009/6/25/306}
 [Viewed August 16, 2009]"
-,annotation="
+,annotation={
 	First posting of expedited RCU to be accepted into -tip.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2009fastRTRCU
@@ -2115,21 +2173,21 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lkml.org/lkml/2009/7/23/294}
 [Viewed August 15, 2009]"
-,annotation="
+,annotation={
 	First posting of simple and fast preemptable RCU.
-"
+}
 }
 
-@InProceedings{JoshTriplett2009RPHash
+@unpublished{JoshTriplett2009RPHash
 ,Author="Josh Triplett"
 ,Title="Scalable concurrent hash tables via relativistic programming"
 ,month="September"
 ,year="2009"
-,booktitle="Linux Plumbers Conference 2009"
-,annotation="
+,note="Linux Plumbers Conference presentation"
+,annotation={
 	RP fun with hash tables.
-	See also JoshTriplett2010RPHash
-"
+	Superseded by JoshTriplett2010RPHash
+}
 }
 
 @phdthesis{MathieuDesnoyersPhD
@@ -2154,9 +2212,9 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://wiki.cs.pdx.edu/rp/}
 [Viewed December 9, 2009]"
-,annotation="
+,annotation={
 	Main Relativistic Programming Wiki.
-"
+}
 }
 
 @conference{PaulEMcKenney2009DeterministicRCU
@@ -2180,9 +2238,9 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://paulmck.livejournal.com/14639.html}
 [Viewed June 4, 2010]"
-,annotation="
+,annotation={
 	Day-one bug in Tree RCU that took forever to track down.
-"
+}
 }
 
 @unpublished{MathieuDesnoyers2009defer:rcu
@@ -2193,10 +2251,10 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://lkml.org/lkml/2009/10/18/129}
 [Viewed December 29, 2009]"
-,annotation="
+,annotation={
 	Mathieu proposed defer_rcu() with fixed-size per-thread pool
 	of RCU callbacks.
-"
+}
 }
 
 @unpublished{MathieuDesnoyers2009VerifPrePub
@@ -2205,10 +2263,10 @@ lot of {Linux} into your technology!!!"
 ,month="December"
 ,year="2009"
 ,note="Submitted to IEEE TPDS"
-,annotation="
+,annotation={
 	OOMem model for Mathieu's user-level RCU mechanical proof of
 	correctness.
-"
+}
 }
 
 @unpublished{MathieuDesnoyers2009URCUPrePub
@@ -2216,15 +2274,15 @@ lot of {Linux} into your technology!!!"
 ,Title="User-Level Implementations of Read-Copy Update"
 ,month="December"
 ,year="2010"
-,url=\url{http://www.computer.org/csdl/trans/td/2012/02/ttd2012020375-abs.html}
-,annotation="
+,url={\url{http://www.computer.org/csdl/trans/td/2012/02/ttd2012020375-abs.html}}
+,annotation={
 	RCU overview, desiderata, semi-formal semantics, user-level RCU
 	usage scenarios, three classes of RCU implementation, wait-free
 	RCU updates, RCU grace-period batching, update overhead,
 	http://www.rdrop.com/users/paulmck/RCU/urcu-main-accepted.2011.08.30a.pdf
 	http://www.rdrop.com/users/paulmck/RCU/urcu-supp-accepted.2011.08.30a.pdf
 	Superseded by MathieuDesnoyers2012URCU.
-"
+}
 }
 
 @inproceedings{HariKannan2009DynamicAnalysisRCU
@@ -2240,7 +2298,8 @@ lot of {Linux} into your technology!!!"
 ,address = {New York, NY, USA}
 ,annotation={
 	Uses RCU to protect metadata used in dynamic analysis.
-}}
+}
+}
 
 @conference{PaulEMcKenney2010SimpleOptRCU
 ,Author="Paul E. McKenney"
@@ -2252,10 +2311,10 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/SimplicityThruOptimization.2010.01.21f.pdf}
 [Viewed October 10, 2010]"
-,annotation="
+,annotation={
 	TREE_PREEMPT_RCU optimizations greatly simplified the old
 	PREEMPT_RCU implementation.
-"
+}
 }
 
 @unpublished{PaulEMcKenney2010LockdepRCU
@@ -2264,12 +2323,11 @@ lot of {Linux} into your technology!!!"
 ,month="February"
 ,year="2010"
 ,day="1"
-,note="Available:
-\url{https://lwn.net/Articles/371986/}
-[Viewed June 4, 2010]"
-,annotation="
+,note="\url{https://lwn.net/Articles/371986/}"
+,annotation={
 	CONFIG_PROVE_RCU, or at least an early version.
-"
+	[Viewed June 4, 2010]
+}
 }
 
 @unpublished{AviKivity2010KVM2RCU
@@ -2280,10 +2338,10 @@ lot of {Linux} into your technology!!!"
 ,note="Available:
 \url{http://www.mail-archive.com/kvm@vger.kernel.org/msg28640.html}
 [Viewed March 20, 2010]"
-,annotation="
+,annotation={
 	Use of RCU permits KVM to increase the size of guest OSes from
 	16 CPUs to 64 CPUs.
-"
+}
 }
 
 @unpublished{HerbertXu2010RCUResizeHash
@@ -2297,7 +2355,19 @@ lot of {Linux} into your technology!!!"
 ,annotation={
 	Use a pair of list_head structures to support RCU-protected
 	resizable hash tables.
-}}
+}
+}
+
+@mastersthesis{AbhinavDuggal2010Masters
+,author="Abhinav Duggal"
+,title="Stopping Data Races Using Redflag"
+,school="Stony Brook University"
+,year="2010"
+,annotation={
+	Data-race detector incorporating RCU.
+	http://www.filesystems.org/docs/abhinav-thesis/abhinav_thesis.pdf
+}
+}
 
 @article{JoshTriplett2010RPHash
 ,author="Josh Triplett and Paul E. McKenney and Jonathan Walpole"
@@ -2310,7 +2380,8 @@ lot of {Linux} into your technology!!!"
 ,annotation={
 	RP fun with hash tables.
 	http://portal.acm.org/citation.cfm?id=1842733.1842750
-}}
+}
+}
 
 @unpublished{PaulEMcKenney2010RCUAPI
 ,Author="Paul E. McKenney"
@@ -2318,12 +2389,11 @@ lot of {Linux} into your technology!!!"
 ,month="December"
 ,day="8"
 ,year="2010"
-,note="Available:
-\url{http://lwn.net/Articles/418853/}
-[Viewed December 8, 2010]"
-,annotation="
+,note="\url{http://lwn.net/Articles/418853/}"
+,annotation={
 	Includes updated software-engineering features.
-"
+	[Viewed December 8, 2010]
+}
 }
 
 @mastersthesis{AndrejPodzimek2010masters
@@ -2338,7 +2408,8 @@ lot of {Linux} into your technology!!!"
 	Reviews RCU implementations and creates a few for OpenSolaris.
 	Drives quiescent-state detection from RCU read-side primitives,
 	in a manner roughly similar to that of Jim Houston.
-}}
+}
+}
 
 @unpublished{LinusTorvalds2011Linux2:6:38:rc1:NPigginVFS
 ,Author="Linus Torvalds"
@@ -2358,7 +2429,8 @@ lot of {Linux} into your technology!!!"
 	of the most expensive parts of path component lookup, which was the
 	d_lock on every component lookup. So I'm seeing improvements of 30-50%
 	on some seriously pathname-lookup intensive loads."
-}}
+}
+}
 
 @techreport{JoshTriplett2011RPScalableCorrectOrdering
 ,author = {Josh Triplett and Philip W. Howard and Paul E. McKenney and Jonathan Walpole}
@@ -2392,12 +2464,12 @@ lot of {Linux} into your technology!!!"
 ,number="US Patent 7,953,778"
 ,month="May"
 ,pages="34"
-,annotation="
+,annotation={
 	Maintains an array of generation numbers to track in-flight
 	updates and keeps an additional level of indirection to allow
 	readers to confine themselves to the desired snapshot of the
 	data structure.
-"
+}
 }
 
 @inproceedings{Triplett:2011:RPHash
@@ -2408,7 +2480,7 @@ lot of {Linux} into your technology!!!"
 ,year = {2011}
 ,pages = {145--158}
 ,numpages = {14}
-,url={http://www.usenix.org/event/atc11/tech/final_files/atc11_proceedings.pdf}
+,url={http://www.usenix.org/event/atc11/tech/final_files/Triplett.pdf}
 ,publisher = {The USENIX Association}
 ,address = {Portland, OR USA}
 }
@@ -2419,27 +2491,52 @@ lot of {Linux} into your technology!!!"
 ,month="July"
 ,day="27"
 ,year="2011"
-,note="Available:
-\url{http://lwn.net/Articles/453002/}
-[Viewed July 27, 2011]"
-,annotation="
+,note="\url{http://lwn.net/Articles/453002/}"
+,annotation={
 	Analysis of the RCU trainwreck in Linux kernel 3.0.
-"
+	[Viewed July 27, 2011]
+}
 }
 
 @unpublished{NeilBrown2011MeetTheLockers
 ,Author="Neil Brown"
-,Title="Meet the Lockers"
+,Title="Meet the {Lockers}"
 ,month="August"
 ,day="3"
 ,year="2011"
 ,note="Available:
 \url{http://lwn.net/Articles/453685/}
 [Viewed September 2, 2011]"
-,annotation="
+,annotation={
 	The Locker family as an analogy for locking, reference counting,
 	RCU, and seqlock.
-"
+}
+}
+
+@inproceedings{Seyster:2011:RFA:2075416.2075425
+,author = {Seyster, Justin and Radhakrishnan, Prabakar and Katoch, Samriti and Duggal, Abhinav and Stoller, Scott D. and Zadok, Erez}
+,title = {Redflag: a framework for analysis of Kernel-level concurrency}
+,booktitle = {Proceedings of the 11th international conference on Algorithms and architectures for parallel processing - Volume Part I}
+,series = {ICA3PP'11}
+,year = {2011}
+,isbn = {978-3-642-24649-4}
+,location = {Melbourne, Australia}
+,pages = {66--79}
+,numpages = {14}
+,url = {http://dl.acm.org/citation.cfm?id=2075416.2075425}
+,acmid = {2075425}
+,publisher = {Springer-Verlag}
+,address = {Berlin, Heidelberg}
+}
+
+@phdthesis{JoshTriplettPhD
+,author="Josh Triplett"
+,title="Relativistic Causal Ordering A Memory Model for Scalable Concurrent Data Structures"
+,school="Portland State University"
+,year="2012"
+,annotation={
+	RCU-protected hash tables, barriers vs. read-side traversal order.
+}
 }
 
 @article{MathieuDesnoyers2012URCU
@@ -2459,5 +2556,153 @@ lot of {Linux} into your technology!!!"
 	RCU updates, RCU grace-period batching, update overhead,
 	http://www.rdrop.com/users/paulmck/RCU/urcu-main-accepted.2011.08.30a.pdf
 	http://www.rdrop.com/users/paulmck/RCU/urcu-supp-accepted.2011.08.30a.pdf
+	http://www.computer.org/cms/Computer.org/dl/trans/td/2012/02/extras/ttd2012020375s.pdf
+}
+}
+
+@inproceedings{AustinClements2012RCULinux:mmapsem
+,author = {Austin Clements and Frans Kaashoek and Nickolai Zeldovich}
+,title = {Scalable Address Spaces Using {RCU} Balanced Trees}
+,booktitle = {Architectural Support for Programming Languages and Operating Systems (ASPLOS 2012)}
+,month = {March}
+,year = {2012}
+,pages = {199--210}
+,numpages = {12}
+,publisher = {ACM}
+,address = {London, UK}
+,url="http://people.csail.mit.edu/nickolai/papers/clements-bonsai.pdf"
+}
+
+@unpublished{PaulEMcKenney2012ELCbattery
+,Author="Paul E. McKenney"
+,Title="Making {RCU} Safe For Battery-Powered Devices"
+,month="February"
+,day="15"
+,year="2012"
+,note="Available:
+\url{http://www.rdrop.com/users/paulmck/RCU/RCUdynticks.2012.02.15b.pdf}
+[Viewed March 1, 2012]"
+,annotation={
+	RCU_FAST_NO_HZ, round 2.
+}
+}
+
+@article{GuillermoVigueras2012RCUCrowd
+,author = {Vigueras, Guillermo and Ordu\~{n}a, Juan M. and Lozano, Miguel}
+,citeulike-article-id = {10632151}
+,citeulike-linkout-0 = {http://dx.doi.org/10.1007/s11227-012-0766-x}
+,citeulike-linkout-1 = {http://www.springerlink.com/content/25762r0874163570}
+,day = {25}
+,doi = {10.1007/s11227-012-0766-x}
+,issn = {0920-8542}
+,journal = {The Journal of Supercomputing}
+,keywords = {linux, simulation}
+,month = apr
+,posted-at = {2012-05-03 09:12:04}
+,priority = {2}
+,title = {{A Read-Copy Update based parallel server for distributed crowd simulations}}
+,url = {http://dx.doi.org/10.1007/s11227-012-0766-x}
+,year = {2012}
+}
+
+
+@unpublished{JonCorbet2012ACCESS:ONCE
+,Author="Jon Corbet"
+,Title="{ACCESS\_ONCE()}"
+,month="August"
+,day="1"
+,year="2012"
+,note="\url{http://lwn.net/Articles/508991/}"
+,annotation={
+	A couple of simple specific compiler optimizations that motivate
+	ACCESS_ONCE().
+}
+}
+
+@unpublished{AlexeyGotsman2012VerifyGraceExtended
+,Author="Alexey Gotsman and Noam Rinetzky and Hongseok Yang"
+,Title="Verifying Highly Concurrent Algorithms with Grace (extended version)"
+,month="July"
+,day="10"
+,year="2012"
+,note="\url{http://software.imdea.org/~gotsman/papers/recycling-esop13-ext.pdf}"
+,annotation={
+	Separation-logic formulation of RCU uses.
+}
+}
+
+@unpublished{PaulMcKenney2012RCUUsage
+,Author="Paul E. McKenney and Silas Boyd-Wickizer and Jonathan Walpole"
+,Title="{RCU} Usage In the Linux Kernel: One Decade Later"
+,month="September"
+,day="17"
+,year="2012"
+,url=http://rdrop.com/users/paulmck/techreports/survey.2012.09.17a.pdf
+,note="Technical report paulmck.2012.09.17"
+,annotation={
+	Overview of the first variant of no-CBs CPUs for RCU.
+}
+}
+
+@unpublished{JonCorbet2012NOCB
+,Author="Jon Corbet"
+,Title="Relocating RCU callbacks"
+,month="October"
+,day="31"
+,year="2012"
+,note="\url{http://lwn.net/Articles/522262/}"
+,annotation={
+	Overview of the first variant of no-CBs CPUs for RCU.
+}
+}
+
+@phdthesis{JustinSeyster2012PhD
+,author="Justin Seyster"
+,title="Runtime Verification of Kernel-Level Concurrency Using Compiler-Based Instrumentation"
+,school="Stony Brook University"
+,year="2012"
+,annotation={
+	Looking for data races, including those involving RCU.
+	Proposal:
+	http://www.fsl.cs.sunysb.edu/docs/jseyster-proposal/redflag.pdf
+	Dissertation:
+	http://www.fsl.cs.sunysb.edu/docs/jseyster-dissertation/redflag.pdf
+}
+}
+
+@unpublished{PaulEMcKenney2013RCUUsage
+,Author="Paul E. McKenney and Silas Boyd-Wickizer and Jonathan Walpole"
+,Title="{RCU} Usage in the {Linux} Kernel: One Decade Later"
+,month="February"
+,day="24"
+,year="2013"
+,note="\url{http://rdrop.com/users/paulmck/techreports/RCUUsage.2013.02.24a.pdf}"
+,annotation={
+	Usage of RCU within the Linux kernel.
+}
+}
+
+@inproceedings{AlexeyGotsman2013ESOPRCU
+,author = {Alexey Gotsman and Noam Rinetzky and Hongseok Yang}
+,title = {Verifying concurrent memory reclamation algorithms with grace}
+,booktitle = {ESOP'13: European Symposium on Programming}
+,year = {2013}
+,pages = {249--269}
+,publisher = {Springer}
+,address = {Rome, Italy}
+,annotation={
+	http://software.imdea.org/~gotsman/papers/recycling-esop13.pdf
+}
+}
+
+@unpublished{PaulEMcKenney2013NoTinyPreempt
+,Author="Paul E. McKenney"
+,Title="Simplifying RCU"
+,month="March"
+,day="6"
+,year="2013"
+,note="\url{http://lwn.net/Articles/541037/}"
+,annotation={
+	Getting rid of TINY_PREEMPT_RCU.
 }
 }
-- 
1.8.1.5

[PATCH tip/core/rcu 3/3] doc: Fix memory-barrier control-dependency example

[Paul E. McKenney]

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

Each control-dependency example needs its barriers between the "if"
condition and the body of the "if" because a control dependency is
a dependency induced by a branch.  This commit makes the needed
adjustment.

Reported-by: Yongming Shen <symingz@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 Documentation/memory-barriers.txt | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index fa5d8a9..c8c42e6 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -531,9 +531,10 @@ dependency barrier to make it work correctly.  Consider the following bit of
 code:
 
 	q = &a;
-	if (p)
+	if (p) {
+		<data dependency barrier>
 		q = &b;
-	<data dependency barrier>
+	}
 	x = *q;
 
 This will not have the desired effect because there is no actual data
@@ -542,9 +543,10 @@ attempting to predict the outcome in advance.  In such a case what's actually
 required is:
 
 	q = &a;
-	if (p)
+	if (p) {
+		<read barrier>
 		q = &b;
-	<read barrier>
+	}
 	x = *q;
 
 
-- 
1.8.1.5

Re: [PATCH tip/core/rcu 2/3] rcu: Update RTFP documentation

[Josh Triplett]

On Sat, Aug 17, 2013 at 06:25:52PM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

Could you mention the BibTeX formatting changes (and the rationale for
them) in the commit message, please?

> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

A couple of comments below (and above); with those fixed,
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

> ---
>  Documentation/RCU/RTFP.txt | 855 +++++++++++++++++++++++++++++----------------
>  1 file changed, 550 insertions(+), 305 deletions(-)
> 
> diff --git a/Documentation/RCU/RTFP.txt b/Documentation/RCU/RTFP.txt
> index 7f40c72..350be9a 100644
> --- a/Documentation/RCU/RTFP.txt
> +++ b/Documentation/RCU/RTFP.txt
> @@ -39,7 +39,7 @@ in read-mostly situations.  This algorithm does take pains to avoid
>  write-side contention and parallelize the other write-side overheads by
>  providing a fine-grained locking design, however, it would be interesting
>  to see how much of the performance advantage reported in 1990 remains
> -in 2004.
> +in 2004 (to say nothing of 2013).

In lieu of updating this again in 9 years, s/2004.*/today./ please?

> +In 2012, Josh Triplett received his Ph.D. with his dissertation
> +covering RCU-protected resizable hash tables and the relationship
> +between memory barriers and read-side traversal order:  If the updater
> +is making changes in the opposite direction from the read-side traveral
> +order, the updater need only execute a memory-barrier instruction,
> +but if in the same direction, the updater needs to wait for a grace
> +period between the individual updates [JoshTriplettPhD].  Also in 2012,

:)

> +after seventeen years of attempts, an RCU paper made it into a top-flight
> +academic journal, IEEE Transactions on Parallel and Distributed Systems
> +[MathieuDesnoyers2012URCU].  A group of researchers in Spain applied

What about the 2010 paper in Operating Systems Review?

> +user-level RCU to crowd simulation [GuillermoVigueras2012RCUCrowd], and
> +another group of researchers in Europe produced a formal description of
> +RCU based on separation logic [AlexeyGotsman2012VerifyGraceExtended],

Oh, interesting, I hadn't seen that one yet.

> +@phdthesis{JoshTriplettPhD
> +,author="Josh Triplett"
> +,title="Relativistic Causal Ordering A Memory Model for Scalable Concurrent Data Structures"

"A Memory Model ..." is a subtitle, so there should be either a : or a
--- after "Ordering".

> +,school="Portland State University"
> +,year="2012"
> +,annotation={
> +	RCU-protected hash tables, barriers vs. read-side traversal order.
> +}

Consider duplicating the summary above about traversal order versus
update order, and memory barriers versus grace periods, into the
annotation.

> +@article{GuillermoVigueras2012RCUCrowd
> +,author = {Vigueras, Guillermo and Ordu\~{n}a, Juan M. and Lozano, Miguel}
> +,citeulike-article-id = {10632151}
> +,citeulike-linkout-0 = {http://dx.doi.org/10.1007/s11227-012-0766-x}
> +,citeulike-linkout-1 = {http://www.springerlink.com/content/25762r0874163570}

Consider dropping these non-standard BibTeX tags; nothing will ever
format them, and you already have the doi below.

> +,day = {25}
> +,doi = {10.1007/s11227-012-0766-x}
> +,issn = {0920-8542}
> +,journal = {The Journal of Supercomputing}
> +,keywords = {linux, simulation}
> +,month = apr
> +,posted-at = {2012-05-03 09:12:04}
> +,priority = {2}
> +,title = {{A Read-Copy Update based parallel server for distributed crowd simulations}}
> +,url = {http://dx.doi.org/10.1007/s11227-012-0766-x}
> +,year = {2012}
> +}
> +
> +
> +@unpublished{JonCorbet2012ACCESS:ONCE

LWN is not "unpublished"; it's at least "misc", and I'd suggest
"article".  Ditto for every other LWN cite in this bibliography.

> +,Author="Jon Corbet"
> +,Title="{ACCESS\_ONCE()}"
> +,month="August"
> +,day="1"
> +,year="2012"
> +,note="\url{http://lwn.net/Articles/508991/}"
> +,annotation={
> +	A couple of simple specific compiler optimizations that motivate
> +	ACCESS_ONCE().
> +}
> +}

- Josh Triplett

Re: [PATCH tip/core/rcu 0/3] Documentation updates for 3.12

[Josh Triplett]

On Sat, Aug 17, 2013 at 06:25:22PM -0700, Paul E. McKenney wrote:
> Hello!
> 
> This series provides a few documentation updates:
> 
> 1.	Update rcu_barrier() documentation to note that it no longer is
> 	guaranteed to wait for a full grace period.  This guarantee was
> 	a victim of energy efficiency.
> 
> 2.	Update RTFP documentation.
> 
> 3.	Fix a control-dependency example in the memory-barriers
> 	documentation.

For patches 1 and 3:
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

I replied to patch 2 with some comments.

- Josh Triplett

Re: [PATCH tip/core/rcu 2/3] rcu: Update RTFP documentation

[Paul E. McKenney]

On Sat, Aug 17, 2013 at 07:46:30PM -0700, Josh Triplett wrote:
> On Sat, Aug 17, 2013 at 06:25:52PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> 
> Could you mention the BibTeX formatting changes (and the rationale for
> them) in the commit message, please?

Good point, done.  Short version: For compatibility with my .bib files,
some of which predate bibtex's ability to handle trailing commas.

> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> 
> A couple of comments below (and above); with those fixed,
> Reviewed-by: Josh Triplett <josh@joshtriplett.org>

I took all but the conversion of the LWN article entry tags, please
see below.

							Thanx, Paul

> > ---
> >  Documentation/RCU/RTFP.txt | 855 +++++++++++++++++++++++++++++----------------
> >  1 file changed, 550 insertions(+), 305 deletions(-)
> > 
> > diff --git a/Documentation/RCU/RTFP.txt b/Documentation/RCU/RTFP.txt
> > index 7f40c72..350be9a 100644
> > --- a/Documentation/RCU/RTFP.txt
> > +++ b/Documentation/RCU/RTFP.txt
> > @@ -39,7 +39,7 @@ in read-mostly situations.  This algorithm does take pains to avoid
> >  write-side contention and parallelize the other write-side overheads by
> >  providing a fine-grained locking design, however, it would be interesting
> >  to see how much of the performance advantage reported in 1990 remains
> > -in 2004.
> > +in 2004 (to say nothing of 2013).
> 
> In lieu of updating this again in 9 years, s/2004.*/today./ please?

Fair point, fixed.

> > +In 2012, Josh Triplett received his Ph.D. with his dissertation
> > +covering RCU-protected resizable hash tables and the relationship
> > +between memory barriers and read-side traversal order:  If the updater
> > +is making changes in the opposite direction from the read-side traveral
> > +order, the updater need only execute a memory-barrier instruction,
> > +but if in the same direction, the updater needs to wait for a grace
> > +period between the individual updates [JoshTriplettPhD].  Also in 2012,
> 
> :)
> 
> > +after seventeen years of attempts, an RCU paper made it into a top-flight
> > +academic journal, IEEE Transactions on Parallel and Distributed Systems
> > +[MathieuDesnoyers2012URCU].  A group of researchers in Spain applied
> 
> What about the 2010 paper in Operating Systems Review?

It is already there, but not visible in this patch:

	2010 produced a simpler preemptible-RCU implementation
	based on TREE_RCU [PaulEMcKenney2010SimpleOptRCU], lockdep-RCU
	[PaulEMcKenney2010LockdepRCU], another resizeable RCU-protected hash
	table [HerbertXu2010RCUResizeHash] (this one consuming more memory,
	but allowing arbitrary changes in hash function, as required for DoS
	avoidance in the networking code), realization of the 2009 RCU-protected
	hash table with atomic node move [JoshTriplett2010RPHash], an update on
	the RCU API [PaulEMcKenney2010RCUAPI].

And:

	@article{JoshTriplett2010RPHash
	,author="Josh Triplett and Paul E. McKenney and Jonathan Walpole"
	,title="Scalable Concurrent Hash Tables via Relativistic Programming"
	,journal="ACM Operating Systems Review"
	,year=2010
	,volume=44
	,number=3
	,month="July"
	,annotation={
	        RP fun with hash tables.
		http://portal.acm.org/citation.cfm?id=1842733.1842750
	}

> > +user-level RCU to crowd simulation [GuillermoVigueras2012RCUCrowd], and
> > +another group of researchers in Europe produced a formal description of
> > +RCU based on separation logic [AlexeyGotsman2012VerifyGraceExtended],
> 
> Oh, interesting, I hadn't seen that one yet.

I am hoping that it will lead to better tools to analyze both RCU
implementations and RCU uses.  ;-)

> > +@phdthesis{JoshTriplettPhD
> > +,author="Josh Triplett"
> > +,title="Relativistic Causal Ordering A Memory Model for Scalable Concurrent Data Structures"
> 
> "A Memory Model ..." is a subtitle, so there should be either a : or a
> --- after "Ordering".

Got it, fixed both in RTFP.txt and in my bibtex database.

> > +,school="Portland State University"
> > +,year="2012"
> > +,annotation={
> > +	RCU-protected hash tables, barriers vs. read-side traversal order.
> > +}
> 
> Consider duplicating the summary above about traversal order versus
> update order, and memory barriers versus grace periods, into the
> annotation.

Done!

> > +@article{GuillermoVigueras2012RCUCrowd
> > +,author = {Vigueras, Guillermo and Ordu\~{n}a, Juan M. and Lozano, Miguel}
> > +,citeulike-article-id = {10632151}
> > +,citeulike-linkout-0 = {http://dx.doi.org/10.1007/s11227-012-0766-x}
> > +,citeulike-linkout-1 = {http://www.springerlink.com/content/25762r0874163570}
> 
> Consider dropping these non-standard BibTeX tags; nothing will ever
> format them, and you already have the doi below.

Done.

> > +,day = {25}
> > +,doi = {10.1007/s11227-012-0766-x}
> > +,issn = {0920-8542}
> > +,journal = {The Journal of Supercomputing}
> > +,keywords = {linux, simulation}
> > +,month = apr
> > +,posted-at = {2012-05-03 09:12:04}
> > +,priority = {2}
> > +,title = {{A Read-Copy Update based parallel server for distributed crowd simulations}}
> > +,url = {http://dx.doi.org/10.1007/s11227-012-0766-x}
> > +,year = {2012}
> > +}
> > +
> > +
> > +@unpublished{JonCorbet2012ACCESS:ONCE
> 
> LWN is not "unpublished"; it's at least "misc", and I'd suggest
> "article".  Ditto for every other LWN cite in this bibliography.

There does seem to be a diverse set of advice out there, with some
agreeing with you on "misc", others advocating for "electronic", and
still others suggesting use of LaBibTex with its "online" tag, and with
the Tex Frequently Asked Questions page saying:

	There is no citation type for URLs, per se, in the standard
	BibTeX styles, though Oren Patashnik (the author of BibTeX)
	is believed to be considering developing one such for use with
	the long-awaited BibTeX version 1.0.

I couldn't find any online .bib files with entries for Linux Weekly News
articles.  Other than my own, of course!  (I know people have cited
them in papers, but Google doesn't see the corresponding .bib files.)

Given all that, I am going to stick with "unpublished" for the moment,
and wait at least one year to see if BibTex version 1.0 comes out.

Seem reasonable?

> > +,Author="Jon Corbet"
> > +,Title="{ACCESS\_ONCE()}"
> > +,month="August"
> > +,day="1"
> > +,year="2012"
> > +,note="\url{http://lwn.net/Articles/508991/}"
> > +,annotation={
> > +	A couple of simple specific compiler optimizations that motivate
> > +	ACCESS_ONCE().
> > +}
> > +}
> 
> - Josh Triplett
> 

Re: [PATCH tip/core/rcu 2/3] rcu: Update RTFP documentation

[Josh Triplett]

On Sun, Aug 18, 2013 at 05:20:02PM -0700, Paul E. McKenney wrote:
> On Sat, Aug 17, 2013 at 07:46:30PM -0700, Josh Triplett wrote:
> > On Sat, Aug 17, 2013 at 06:25:52PM -0700, Paul E. McKenney wrote:
> > > +In 2012, Josh Triplett received his Ph.D. with his dissertation
> > > +covering RCU-protected resizable hash tables and the relationship
> > > +between memory barriers and read-side traversal order:  If the updater
> > > +is making changes in the opposite direction from the read-side traveral
> > > +order, the updater need only execute a memory-barrier instruction,
> > > +but if in the same direction, the updater needs to wait for a grace
> > > +period between the individual updates [JoshTriplettPhD].  Also in 2012,
> > 
> > :)
> > 
> > > +after seventeen years of attempts, an RCU paper made it into a top-flight
> > > +academic journal, IEEE Transactions on Parallel and Distributed Systems
> > > +[MathieuDesnoyers2012URCU].  A group of researchers in Spain applied
> > 
> > What about the 2010 paper in Operating Systems Review?
> 
> It is already there, but not visible in this patch:
> 
> 	2010 produced a simpler preemptible-RCU implementation
> 	based on TREE_RCU [PaulEMcKenney2010SimpleOptRCU], lockdep-RCU
> 	[PaulEMcKenney2010LockdepRCU], another resizeable RCU-protected hash
> 	table [HerbertXu2010RCUResizeHash] (this one consuming more memory,
> 	but allowing arbitrary changes in hash function, as required for DoS
> 	avoidance in the networking code), realization of the 2009 RCU-protected
> 	hash table with atomic node move [JoshTriplett2010RPHash], an update on
> 	the RCU API [PaulEMcKenney2010RCUAPI].
> 
> And:
> 
> 	@article{JoshTriplett2010RPHash
> 	,author="Josh Triplett and Paul E. McKenney and Jonathan Walpole"
> 	,title="Scalable Concurrent Hash Tables via Relativistic Programming"
> 	,journal="ACM Operating Systems Review"
> 	,year=2010
> 	,volume=44
> 	,number=3
> 	,month="July"
> 	,annotation={
> 	        RP fun with hash tables.
> 		http://portal.acm.org/citation.cfm?id=1842733.1842750
> 	}

Right, I saw it in the file when I checked; I meant, that journal paper
seems to contradict "after seventeen years of attempts, an RCU paper
made it into a top-flight academic journal". :)

> > > +,day = {25}
> > > +,doi = {10.1007/s11227-012-0766-x}
> > > +,issn = {0920-8542}
> > > +,journal = {The Journal of Supercomputing}
> > > +,keywords = {linux, simulation}
> > > +,month = apr
> > > +,posted-at = {2012-05-03 09:12:04}
> > > +,priority = {2}
> > > +,title = {{A Read-Copy Update based parallel server for distributed crowd simulations}}
> > > +,url = {http://dx.doi.org/10.1007/s11227-012-0766-x}
> > > +,year = {2012}
> > > +}
> > > +
> > > +
> > > +@unpublished{JonCorbet2012ACCESS:ONCE
> > 
> > LWN is not "unpublished"; it's at least "misc", and I'd suggest
> > "article".  Ditto for every other LWN cite in this bibliography.
> 
> There does seem to be a diverse set of advice out there, with some
> agreeing with you on "misc", others advocating for "electronic", and
> still others suggesting use of LaBibTex with its "online" tag, and with
> the Tex Frequently Asked Questions page saying:
> 
> 	There is no citation type for URLs, per se, in the standard
> 	BibTeX styles, though Oren Patashnik (the author of BibTeX)
> 	is believed to be considering developing one such for use with
> 	the long-awaited BibTeX version 1.0.
> 
> I couldn't find any online .bib files with entries for Linux Weekly News
> articles.  Other than my own, of course!  (I know people have cited
> them in papers, but Google doesn't see the corresponding .bib files.)
> 
> Given all that, I am going to stick with "unpublished" for the moment,
> and wait at least one year to see if BibTex version 1.0 comes out.

Several different tags make sense, but "unpublished" isn't one of them.
"unpublished" exists for entirely un-reviewed works such as self-hosted
PDFs.  LWN has editorial standards.  Thus, of the standard tags that
work with all BibTeX styles, I think either "article" or "misc" would
make more sense than "unpublished".

An example from one of my own .bib files:

@article{tiny-rcu-lwn,
author = "Paul E. McKenney",
title = {{RCU: The Bloatwatch Edition}},
journal = "Linux Weekly News",
month = "March",
year = "2009",
day = "17",
url = {https://lwn.net/Articles/323929/}
}

(With the obvious change that since you don't use "url" in your .bib
files, that should go in "howpublished" or "note" instead.)

- Josh Triplett

Re: [PATCH tip/core/rcu 2/3] rcu: Update RTFP documentation

[Paul E. McKenney]

On Sun, Aug 18, 2013 at 05:38:51PM -0700, Josh Triplett wrote:
> On Sun, Aug 18, 2013 at 05:20:02PM -0700, Paul E. McKenney wrote:
> > On Sat, Aug 17, 2013 at 07:46:30PM -0700, Josh Triplett wrote:
> > > On Sat, Aug 17, 2013 at 06:25:52PM -0700, Paul E. McKenney wrote:
> > > > +In 2012, Josh Triplett received his Ph.D. with his dissertation
> > > > +covering RCU-protected resizable hash tables and the relationship
> > > > +between memory barriers and read-side traversal order:  If the updater
> > > > +is making changes in the opposite direction from the read-side traveral
> > > > +order, the updater need only execute a memory-barrier instruction,
> > > > +but if in the same direction, the updater needs to wait for a grace
> > > > +period between the individual updates [JoshTriplettPhD].  Also in 2012,
> > > 
> > > :)
> > > 
> > > > +after seventeen years of attempts, an RCU paper made it into a top-flight
> > > > +academic journal, IEEE Transactions on Parallel and Distributed Systems
> > > > +[MathieuDesnoyers2012URCU].  A group of researchers in Spain applied
> > > 
> > > What about the 2010 paper in Operating Systems Review?
> > 
> > It is already there, but not visible in this patch:
> > 
> > 	2010 produced a simpler preemptible-RCU implementation
> > 	based on TREE_RCU [PaulEMcKenney2010SimpleOptRCU], lockdep-RCU
> > 	[PaulEMcKenney2010LockdepRCU], another resizeable RCU-protected hash
> > 	table [HerbertXu2010RCUResizeHash] (this one consuming more memory,
> > 	but allowing arbitrary changes in hash function, as required for DoS
> > 	avoidance in the networking code), realization of the 2009 RCU-protected
> > 	hash table with atomic node move [JoshTriplett2010RPHash], an update on
> > 	the RCU API [PaulEMcKenney2010RCUAPI].
> > 
> > And:
> > 
> > 	@article{JoshTriplett2010RPHash
> > 	,author="Josh Triplett and Paul E. McKenney and Jonathan Walpole"
> > 	,title="Scalable Concurrent Hash Tables via Relativistic Programming"
> > 	,journal="ACM Operating Systems Review"
> > 	,year=2010
> > 	,volume=44
> > 	,number=3
> > 	,month="July"
> > 	,annotation={
> > 	        RP fun with hash tables.
> > 		http://portal.acm.org/citation.cfm?id=1842733.1842750
> > 	}
> 
> Right, I saw it in the file when I checked; I meant, that journal paper
> seems to contradict "after seventeen years of attempts, an RCU paper
> made it into a top-flight academic journal". :)

Ah, from what I can see, OSR is on its way up, but still mid-ranks.
(Some years back, it was low-end -- unreviewed.)

> > > > +,day = {25}
> > > > +,doi = {10.1007/s11227-012-0766-x}
> > > > +,issn = {0920-8542}
> > > > +,journal = {The Journal of Supercomputing}
> > > > +,keywords = {linux, simulation}
> > > > +,month = apr
> > > > +,posted-at = {2012-05-03 09:12:04}
> > > > +,priority = {2}
> > > > +,title = {{A Read-Copy Update based parallel server for distributed crowd simulations}}
> > > > +,url = {http://dx.doi.org/10.1007/s11227-012-0766-x}
> > > > +,year = {2012}
> > > > +}
> > > > +
> > > > +
> > > > +@unpublished{JonCorbet2012ACCESS:ONCE
> > > 
> > > LWN is not "unpublished"; it's at least "misc", and I'd suggest
> > > "article".  Ditto for every other LWN cite in this bibliography.
> > 
> > There does seem to be a diverse set of advice out there, with some
> > agreeing with you on "misc", others advocating for "electronic", and
> > still others suggesting use of LaBibTex with its "online" tag, and with
> > the Tex Frequently Asked Questions page saying:
> > 
> > 	There is no citation type for URLs, per se, in the standard
> > 	BibTeX styles, though Oren Patashnik (the author of BibTeX)
> > 	is believed to be considering developing one such for use with
> > 	the long-awaited BibTeX version 1.0.
> > 
> > I couldn't find any online .bib files with entries for Linux Weekly News
> > articles.  Other than my own, of course!  (I know people have cited
> > them in papers, but Google doesn't see the corresponding .bib files.)
> > 
> > Given all that, I am going to stick with "unpublished" for the moment,
> > and wait at least one year to see if BibTex version 1.0 comes out.
> 
> Several different tags make sense, but "unpublished" isn't one of them.
> "unpublished" exists for entirely un-reviewed works such as self-hosted
> PDFs.  LWN has editorial standards.  Thus, of the standard tags that
> work with all BibTeX styles, I think either "article" or "misc" would
> make more sense than "unpublished".
> 
> An example from one of my own .bib files:
> 
> @article{tiny-rcu-lwn,
> author = "Paul E. McKenney",
> title = {{RCU: The Bloatwatch Edition}},
> journal = "Linux Weekly News",
> month = "March",
> year = "2009",
> day = "17",
> url = {https://lwn.net/Articles/323929/}
> }
> 
> (With the obvious change that since you don't use "url" in your .bib
> files, that should go in "howpublished" or "note" instead.)

I might do this at some point, but don't want to do it twice.  If Patashnik
hasn't released a new BibTeX by this time next year, I will probably go
with "misc".

I do agree that LWN deserves more respect, but on the other hand, RTFP.txt
has been using "unpublished" since January 2008, so I am willing to hold
off another year.  ;-)

							Thanx, Paul

Re: [PATCH tip/core/rcu 0/3] Documentation updates for 3.12

[Rob Landley]

On 08/17/2013 08:25:22 PM, Paul E. McKenney wrote:
> Hello!
> 
> This series provides a few documentation updates:
> 
> 1.	Update rcu_barrier() documentation to note that it no longer is
> 	guaranteed to wait for a full grace period.  This guarantee was
> 	a victim of energy efficiency.
> 
> 2.	Update RTFP documentation.
> 
> 3.	Fix a control-dependency example in the memory-barriers
> 	documentation.

Acked-by: Rob Landley <rob@landley.net>

(I'm just happy you don't have gratuitous quizzes mixed through it...)

Rob

Re: [PATCH tip/core/rcu 0/3] Documentation updates for 3.12

[Paul E. McKenney]

On Tue, Aug 20, 2013 at 02:09:30AM -0500, Rob Landley wrote:
> On 08/17/2013 08:25:22 PM, Paul E. McKenney wrote:
> >Hello!
> >
> >This series provides a few documentation updates:
> >
> >1.	Update rcu_barrier() documentation to note that it no longer is
> >	guaranteed to wait for a full grace period.  This guarantee was
> >	a victim of energy efficiency.
> >
> >2.	Update RTFP documentation.
> >
> >3.	Fix a control-dependency example in the memory-barriers
> >	documentation.
> 
> Acked-by: Rob Landley <rob@landley.net>

Glad you like it!

> (I'm just happy you don't have gratuitous quizzes mixed through it...)

That comes later.  ;-)

There actually is a method to the quick-quiz madness, but perhaps
something for another time.

							Thanx, Paul

[PATCH tip/core/rcu 1/3] rcu: Fix rcu_barrier() documentation

[Paul E. McKenney]

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

There was a time when rcu_barrier() was guaranteed to wait for at least
a grace period, but that time ended due to energy-efficiency concerns.
So now rcu_barrier() is a no-op if there are no RCU callbacks queued in
the system.  This commit updates the documentation to reflect this change.

Now, rcu_barrier() often does wait for a grace period, so, one could
imagine some modification to rcu_barrier() to more efficiently handle
cases where both rcu_barrier() and a grace period are needed.  But this
must wait until someone shows a real-world need for a change.

Reported-by: Bob Copeland <bob@cozybit.com>
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
---
 Documentation/RCU/rcubarrier.txt | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/Documentation/RCU/rcubarrier.txt b/Documentation/RCU/rcubarrier.txt
index 2e319d1..b10cfe7 100644
--- a/Documentation/RCU/rcubarrier.txt
+++ b/Documentation/RCU/rcubarrier.txt
@@ -70,10 +70,14 @@ in realtime kernels in order to avoid excessive scheduling latencies.
 
 rcu_barrier()
 
-We instead need the rcu_barrier() primitive. This primitive is similar
-to synchronize_rcu(), but instead of waiting solely for a grace
-period to elapse, it also waits for all outstanding RCU callbacks to
-complete. Pseudo-code using rcu_barrier() is as follows:
+We instead need the rcu_barrier() primitive.  Rather than waiting for
+a grace period to elapse, rcu_barrier() waits for all outstanding RCU
+callbacks to complete.  Please note that rcu_barrier() does -not- imply
+synchronize_rcu(), in particular, if there are no RCU callbacks queued
+anywhere, rcu_barrier() is within its rights to return immediately,
+without waiting for a grace period to elapse.
+
+Pseudo-code using rcu_barrier() is as follows:
 
    1. Prevent any new RCU callbacks from being posted.
    2. Execute rcu_barrier().
-- 
1.8.1.5